WO2019145909A2

WO2019145909A2 - Radar-reflective periodic array of conductive strips, slots and marking tape

Info

Publication number: WO2019145909A2
Application number: PCT/IB2019/050637
Authority: WO
Inventors: Susannah C. Clear; Edmund J. Ring; Robert A. Sainati; Mohsen Salehi; Thomas P. Hedblom; Marcel DOERING; Christian Weinmann; Joern Buettner
Original assignee: 3M Innovative Properties Company
Priority date: 2018-01-26
Filing date: 2019-01-25
Publication date: 2019-08-01
Also published as: WO2019145909A3

Abstract

A pathway article that includes a radar reflective structure with a large radar cross section (RCS) in a compact planar structure. The radar reflective structure may include a plurality of elements that act as antennae and may be spaced appropriately on a planar surface creating a radar reflecting surface. The antennae may be slots in a conductive sheet, or conductive strips. Selecting the spacing between the antennae may cause constructive interference and reflection substantially opposite the direction of the incident radar radiation. Pathway articles may also include at least one additional feature that may be detected by other sensors. Examples of other features include retroreflective features detectable by the human eye, visible camera and similar sensors. This redundancy in the detectable features of the pathway article may enable use of sensor fusion to provide greater confidence of detection of the pathway article under a wide range of conditions.

Description

RADAR-REFLECTIVE PERIODIC ARRAY OF CONDUCTIVE STRIPS, SLOTS AND

MARKING TAPE

TECHNICAL FIELD

The disclosure relates to roadway marking.

BACKGROUND

Automotive radars in a narrowband range are widely implemented for applications such as adaptive cruise control and blind spot monitoring. There has been global activity toward automotive radar systems that may distinguish objects on a roadway with greater accuracy than narrowband systems. A larger bandwidth radar system may enable higher spatial resolution, compared to a narrow bandwidth system, which may limit resolution. Some vehicle radar system manufacturers have begun to develop and implement higher frequency and wider bandwidth radar systems.

SUMMARY

In general, this disclosure is directed to a pathway article that includes a radar reflective structure with a large radar cross section (RCS) in a compact planar structure. A pathway article may include a pathway marking tape, traffic cone or barrel, stop sign, and similar articles. The radar reflective structure may include a plurality of elements that act as antennae and may be spaced appropriately on a planar surface creating a radar reflecting surface. Selecting the spacing between the antennae may cause constructive interference leading to reflection in the backscatter direction, substantially opposite the direction of the incident radar radiation. The radar reflecting structures may provide cues for radar equipped vehicles traveling along a pathway that includes a pathway article of this disclosure.

Pathway articles of this disclosure may also include at least one additional feature along with these radar reflective structures that may be detected by other sensors on a vehicle. Examples of other features include retroreflective features detectable by the human eye, visible camera, infrared camera, and similar sensors. This redundancy in the detectable features of the pathway article may enable use of sensor fusion to provide greater confidence of detection of the pathway article under a wider range of conditions and to enable distinction between marking and other radar-reflective objects, such as other vehicles, in the field of view of the radar system.

In one example, the disclosure is directed to a radar reflecting structure device, the device comprising: a first radar reflective element; and a second radar reflective element, wherein: the second radar reflective element is substantially parallel to the first radar reflective element; a radar signal that reflects off the first radar reflective element results in a first reflected signal; the radar signal that reflects off the second radar reflective element results in a second reflected signal; the second reflected signal causes a phase interference in the first reflected signal; the phase interference causes the first reflected signal and the second reflected signal to form a reflected beam, wherein the reflected beam comprises a direction of travel substantially opposite to a direction of travel of the radar signal. In another example, the disclosure is directed to an article comprising: a sheet material comprising: a continuous base sheet including an upper surface and a lower surface; a sensable layer applied to the upper surface of the continuous base sheet, wherein the sensable layer comprises a protective layer, wherein the sheet material comprises a long axis and a short axis; a radar reflecting structure: wherein the radar reflective structure is disposed between the sensable layer and the continuous base sheet, in the plane of the continuous base sheet, the radar reflective structure comprising: a first radar reflective element; and a second radar reflective element, wherein: the second radar reflective element is substantially parallel to the first radar reflective element; a radar signal that reflects off the first radar reflective element results in a first reflected signal; the radar signal that reflects off the second radar reflective element results in a second reflected signal; the second reflected signal causes a phase interference in the first reflected signal; the phase interference causes the first reflected signal and the second reflected signal to form a reflected beam, wherein the reflected beam comprises a direction of travel substantially opposite to a direction of travel of the radar signal.

In another example, the disclosure is directed to a system for vehicles on a traffic-bearing surface, the system comprising : a pathway configured to support vehicle traffic; a pathway-article assisted vehicle (PAAV) comprising: one or more radar transceiver devices; one or more sensor devices; one or more processor circuits configured to interpret a first signal from the one or more radar transceiver devices and a second signal from the one or more sensor devices; a pathway article comprising a radar reflecting structure, wherein the pathway article is arranged on the pathway within a field of regard (FOR) of the one or more radar transceiver devices, and wherein the radar reflective structure comprises: a first radar reflective element; and a second radar reflective element, wherein: the second radar reflective element is substantially parallel to the first radar reflective element; a radar signal that reflects off the first radar reflective element results in a first reflected signal; the radar signal that reflects off the second radar reflective element results in a second reflected signal; the second reflected signal causes a phase interference in the first reflected signal; the phase interference causes the first reflected signal and the second reflected signal to form a reflected beam, wherein the reflected beam comprises a direction of travel substantially opposite to a direction of travel of the radar signal.

In another example, the disclosure is directed to a method for making a marking tape material comprising: providing a continuous base sheet including an upper surface and a lower surface; applying a sensable layer to the upper surface of the continuous base sheet; applying a continuous conformance layer to the lower surface of the continuous base sheet; adding a radar reflecting structure device disposed between the sensable layer and the continuous base sheet, in a plane of the continuous base sheet, wherein the radar reflective structure comprises a first radar reflective element and a second radar reflective element.

The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual block diagram illustrating an example system including roadway marking with radar reflecting structures.

FIGS. 2 A - 2D are conceptual diagrams illustrating example arrangements of radar reflecting structures within marking tape according to one or more techniques of this disclosure.

FIG. 3 is a conceptual diagram illustrating an example arrangement of radar reflecting structures spaced within marking tape to form a code according to one or more techniques of this disclosure.

FIG. 4 is a conceptual diagram illustrating an example vehicle equipped with radar transceiver devices and interaction with a marking tape according to one or more techniques of this disclosure.

FIGS. 5A - 5B are conceptual diagrams illustrating an example resonant radar reflecting structures according to one or more techniques of this disclosure.

FIGS. 6A - 6C are conceptual diagrams illustrating an example resonant radar reflecting structures with a radius according to one or more techniques of this disclosure.

FIGS. 7A - 7B are diagrams illustrating a detailed view of the slot radar reflecting structure according to one or more techniques of this disclosure.

FIGS. 8 A - 8B are conceptual diagrams illustrating an example non-resonant radar reflecting structures according to one or more techniques of this disclosure.

FIGS. 9A - 9B are conceptual diagrams illustrating an example non-resonant radar reflecting structures with a radius according to one or more techniques of this disclosure.

FIG. 10 is a diagram illustrating a side view of an example reflection and scattering of a radar beam with a radar reflecting structures of this disclosure.

FIG. 11 is a diagram illustrating a top view of an example reflection and scattering of a radar beam with a radar reflecting structures of this disclosure.

FIG. 12 is a block diagram illustrating an example compact planar structure that includes a radar reflecting structures according to one or more techniques of this disclosure.

FIGS. 13A and 13B are conceptual diagrams illustrating example marking tape with a retroreflective sensable layer and a radar reflecting structures layer according to one or more techniques of this disclosure.

FIG. 14 is a flow chart illustrating an example technique for making a marking tape according to one or more techniques of this disclosure.

DETAILED DESCRIPTION

This disclosure is directed to a pathway article that includes a radar reflective structure with a large radar cross section (RCS) in a compact planar structure. A pathway article may include a pathway marking tape, traffic cone or barrel, stop sign, and similar articles. The radar reflective structure may include a plurality of elements that act as antennae and may be spaced appropriately on a planar surface creating a radar reflecting surface. There may be one or more rows of these antennae that form a periodic structure which can interact with the radar’s electromagnetic wave. The dimensions and spacing between the rows of antennae is a function of expected angle of incidence and the expected frequency of the radar. Selecting the spacing between the antennae causes constructive interference leading to a reflection of energy in the backscatter direction.

A vehicle with radar systems or other sensors that takes cues from a vehicle pathway may be called a pathway-article assisted vehicle (PAAV). Some examples of PAAVs may include the fully autonomous vehicles, a vehicle with advanced Automated Driver Assist Systems (ADAS), as well as unmanned aerial vehicles (UAVs) (aka drones), human flight transport devices, underground pit mining ore carrying vehicles, forklifts, factory part or tool transport vehicles, ships and other watercraft and similar vehicles. A vehicle pathway may be a road, highway, a warehouse aisle, factory floor or a pathway not connected to the earth’s surface. The vehicle pathway may include portions not limited to the pathway itself. In the example of a road, the pathway may include the road shoulder, physical structures near the pathway such as toll booths, railroad crossing equipment, traffic lights, the sides of a mountain, guardrails, and generally encompassing any other properties or characteristics of the pathway or objects/structures in proximity to the pathway.

This disclosure also describes pathway articles that include these radar reflective structures and at least one additional feature that may be detected by other sensor systems mounted on the PAAV, such as an automobile. Examples of other features include retroreflective features detectable by the human eye, visible camera, infrared camera, and similar sensors. Other features may be detectable for example by LIDAR, or a magnetic detector. The radar reflective structures and the additional feature(s) may be located in the same region of the pathway article, such as marking tape, or adjacent to each other. This redundancy in the detectable features of the pathway article may enable use of sensor fusion to provide greater confidence of detection of the pathway article under a wider range of conditions and to enable distinction between marking and other radar-reflective objects, such as other vehicles, in the field of view of the radar system. In some examples, a magnetically detectable component may be applied in a spatially separated and distinct location from the radar reflecting structure.

One example of this invention is a pavement marking tape where the radar reflective structures are spaced along the axial direction of the pavement marking tape, and where they are positioned at an angle relative to the axial direction of vehicle travel. For pavement marking tapes that delineate lane boundaries, in some examples this angle may be between zero to ninety degrees relative to the axial direction of vehicle travel. As the vehicle equipped with a radar travels along the roadway, this configuration would generate a periodic response of backscattered power. When illuminated with a frequency modulated continuous wave (FMCW) signal, such as in some automotive radars, the radar system may observe a shift in frequency at which the reflected signal occurs for a given array as the vehicle moves relative to the array. The time delay associated with this peak may assist the PAAV to determine the distance of the tape from the radar transceiver unit.

FIG. 1 is a conceptual diagram illustrating an example system 100 including pathway marking tape with radar reflecting structures, according to one or more techniques of this disclosure. System 100 includes PAAV 110, vehicle pathway 130, and one or more pathway articles 132A-132C (collectively, “pathway articles 132”).

In some examples, pathway article 132 include a pavement marking tape, a traffic sign (e.g., a stop sign, yield sign, mile marker, etc.), license plate, a decal or similar article attached to a vehicle, a temporary traffic sign (e.g., a traffic cone or barrel), or other infrastructure articles. In some examples, a pathway article may also include any item along a pathway, such as an article of clothing, for example on a construction worker, a bicycle, and similar articles. For example, as illustrated in FIG. 1, pathway article 132A includes a pavement marking tape indicating an outer edge of vehicle pathway 130 (e.g., for traffic traveling left to right), pathway article 132B includes a pavement marking indicating a center line of vehicle pathway 130 (e.g., dividing traffic that travels left to right from traffic traveling right to left), and pathway article 132C indicates another outer edge of vehicle pathway 130 (e.g., for traffic traveling left to right).

In accordance with techniques of this disclosure, each pathway article of pathway articles 132 includes one or more radar reflecting structures. For example, as illustrated in FIG. 1, pathway article 132A includes radar reflecting structures 134AI-134A_N, pathway article 132B includes radar reflecting structures 134BI-134B_N, and pathway article 132C includes radar reflecting structures 134Ci- 134C_N (collectively,“radar reflecting structures 134”). In some examples, each of radar reflecting structures 134 is configured to receive radar radiation and reflect the radar radiation in the direction from which the radar radiation was received. For example, radar reflecting structures 134 may be configured to reflect radar radiation of a particular wavelength, such as radiation with a frequency between approximately 24 GHz and approximately 28 GHz or a frequency between approximately 76GHz and approximately 8 lGHz. It is to be understood that the wavelengths are example wavelengths only and that other ranges of wavelengths are possible. In some examples, radar reflecting structures 134 may include a plurality of antennas, which may be linear slot antennas, u-shaped antennas, or other shapes of antennas. In some examples, a plurality of radar reflective structures may also be referred to as a radar reflective array. A radar reflecting structure may also be referred to as an RCS device.

In some examples, each of pathway articles 132 may include additional human or machine detectable features. For example, pathway articles 132 may include a colored (e.g., yellow, white, etc.) surface detectable by a human operating or located within PAAV 110. In other words, at least a portion of pathway articles 132 may be colored in the human-visible light spectrum, such that pathway articles 132 are perceptible by humans. As another example, at least a portion of pathway articles 132 may include text, images, or other visual information. Similarly, pathway articles 132 may include a machine- perceptible surface. For example, at least a portion of pathway articles 132 may detectable via an infrared camera (e.g., an infrared camera onboard PAAV 110).

System 100 includes PAAV 110 that may operate on vehicle pathway 130. As described herein, PAAV generally refers to a vehicle that may interpret the vehicle pathway and the vehicle’s environment, such as other vehicles or objects. A PAAV may interpret information from one or more sensors (e.g., cameras, radar devices, etc.), make decisions based on the information from the one or more sensors, and take actions to navigate the vehicle pathway.

PAAV 110 of system 100 may be an autonomous or semi -autonomous vehicle, such as an ADAS. In some examples PAAV 110 may include occupants that may take full or partial control of PAAV 110. PAAV 110 may be any type of vehicle designed to carry passengers or freight including small electric powered vehicles, large trucks or lorries with trailers, vehicles designed to carry crushed ore within an underground mine, or similar types of vehicles. PAAV 110 may include lighting, such as headlights in the visible light spectrum as well as light sources in other spectrums, such as infrared. PAAV 110 may include other sensors such as radar, sonar, LIDAR, GPS, and communication links for the purpose of sensing the vehicle pathway, other vehicles in the vicinity, environmental conditions around the vehicle, and for communicating with infrastructure.

As shown in FIG. 1, PAAV 110 of system 100 may include one or more image capture devices 150, one or more radar devices 152, and computing device 140. PAAV 110 may include additional components not shown in FIG. 1 such as engine temperature sensor, speed sensor, tire pressure sensor, air temperature sensors, an inclinometer, accelerometers, light sensor, and similar sensing components.

Image capture devices 150 may convert light or electromagnetic radiation sensed by one or more image capture sensors into information, such as digital image or bitmap comprising a set of pixels. Each pixel may have chrominance and/or luminance components that represent the intensity and/or color of light or electromagnetic radiation. Image capture devices 150 may include one or more image capture sensors and one or more light sources. In some examples, image capture devices 150 may include image capture sensors and light sources in a single integrated device. In other examples, image capture sensors or light sources may be separate from or otherwise not integrated in image capture devices 150.

Examples of image capture sensors within image capture devices 150 may include semiconductor charge- coupled devices (CCD) or active pixel sensors in complementary metal-oxide-semiconductor (CMOS) or N-type metal-oxide-semiconductor (NMOS, Live MOS) technologies. Digital sensors include flat panel detectors. In one example, image capture devices 150 includes at least two different sensors for detecting light in two different wavelength spectrums.

In general, image capture devices 150 may be used to gather information about a pathway. Image capture devices 150 may have a fixed field of view or may have an adjustable field of view. An image capture device with an adjustable field of view may be configured to pan left and right, up and down relative to PAAV 110 as well as be able to widen or narrow focus. Image capture devices 150 may capture images of vehicle pathway 130, which may include images of lane markings, centerline markings, edge of roadway or shoulder markings, as well as the general shape of the vehicle pathway 130.

Responsive to capturing images of vehicle pathway 130, image capture devices 150 may generate information indicative of the images and send the image information to computing device 140.

PAAV 110 includes one or more radar devices 152. Each radar device of radar devices 152 include a radar transmitter configured to emit radar radiation (e.g., radio waves) and one or more radar receivers configured to detect radar radiation. In some examples, one or more radar receivers may be placed to measure off-angle shift in power and/or frequency. In some examples, radar devices 152 emit radar radiation with a frequency between approximately 24 GHz with approximately a 200 MHz bandwidth, or a frequency between approximately 76GHz and approximately 81 GHz. It is to be understood that the frequencies listed are merely example frequencies and that other radar frequencies may be used.

Radar devices 152 may be include stationary radar devices 152, such that the radar transmitter emits radar radiation in a single direction and the radar receiver receives or detects radar radiation from a single direction. In some examples, one or more of radar devices 152 are pivotable or rotatable, such that the radar transmitter emits radiation in a range of directions (e.g., 45 degrees in a horizontal direction and 45 degrees in a vertical direction) and the radar receiver receives radar radiation from a range of directions. In some examples, the radar device may be physically stationary, but the beam may be steered (e.g. via a phased array.) In some examples, radar devices 152 detect radar radiation and output radar information about the detected radar radiation to computing device 140. The region illuminated by the transmitted radar radiation and in which the radar receiver receives radar radiation may be referred to as a radar devices field of regard (FOR).

In the example of FIG. 1, computing device 140 includes an interpretation component 142 and a vehicle control component 144. Components 142 and 144 may perform operations described herein using hardware, hardware and software, hardware and firmware, or a mixture therein. Computing device 140 may execute components 142 and 144 with one or more processors. Computing device 140 may execute any of components 142 and 144 as or within a virtual machine executing on underlying hardware.

In some examples, interpretation component 142 may information from image capture devices 150, radar devices 152, or both, and determine one or more characteristics of vehicle pathway 130. For example, computing device 140 may receive image information from image capture devices 150.

Responsive to receiving the image information, interpretation component 142 of computing device 140 may perform image processing (e.g., filtering, amplification, and the like) and image recognition on the received image information. For example, interpretation component 15 may determine (e.g., using image recognition techniques) that the image information includes information indicative of pathway articles 132 and that pathway articles 132 correspond to pavement lane markings. Responsive to determining that pathway articles 132 correspond to pavement lane markings, interpretation component 142 may determine a position of vehicle 110 within a lane of pathway 130.

Similarly, interpretation component 142 may determine a position of vehicle 110 based at least in part on radar information received from radar devices 152. For example, radar devices 152 may output radar information that indicates an object was detected, a distance to the object, a direction of the object relative to vehicle 110, or any combination therein. In some examples, interpretation component 142 determines the direction and distance to the object (e.g., pathway article 132) based on the received radar information. Interpretation component 142 may determine that the radar information indicates the radar radiation was received from (e.g., reflected off) a pathway article, such as a pavement marking tape. Responsive to determining the radar information indicates that the radar radiation was received from a pavement marking tape, interpretation component 142 may determine a position of vehicle 110 with a lane of pathway 130. For example, interpretation component 142 may determine a distance to the pavement marking tape based on the received radar information. Responsive to determining the position of vehicle 110 within vehicle pathway 130, interpretation component 142 may output information about the vehicle position to vehicle control component 144. To simplify the description of the figures, this disclosure may focus on pathway articles that are pavement marking tapes. However, as described above, a pathway article may include other objects, including objects in which a marking tape according the techniques of this disclosure is affixed. Some examples may include guard rails, such as concrete barriers, traffic barrels, curbs and similar articles.

Vehicle control component 144 may control or adjust operation of PAAV 110 based on the information received from interpretation component. For example, vehicle control component 144 may receive, from interpretation component 142, information indicating that vehicle 110 is approaching a pavement marking tape and may output a command to an electronic control unit (ECU) of vehicle 110 to apply a force to the steering to keep vehicle 110 within its current lane.

In some examples, computing device 140 may use information from interpretation component 142 to generate notifications for a user of PAAV 110, e.g., notifications that indicate a characteristic or condition of vehicle pathway 130. For example, responsive to receiving information indicating that vehicle 110 is approaching a pavement marking tape, vehicle control component 144 may output a notification (e.g., audible, graphical, or tactile) to warn an occupant of vehicle 110 that vehicle 110 is approaching the pavement marking.

Pathway articles that include radar reflective structure of this disclosure may have advantages over other types of pathway articles. Including radar reflective structures in the pathway article may increase the ability of a PAAV to detect a pathway in various conditions (e.g., inclement weather conditions), reduce the cost and complexity of components utilized by the PAAV to detect the pathway (e.g., by eliminating the need for other more costly components such as LIDAR), provide redundant techniques for the PAAV to detect the pathway, or a combination therein. For example, computing device 140 of PAAV 110 may combined the input from visual, radar and other sensors to provide a more complete interpretation of the vehicle pathway. For example, a lane assistant system based on optical camera systems may detect and analyze the course of the lane mainly by detection of the contrast between road surface and pavement marking. In hazardous or extreme weather condition like fog, snow, or other precipitation, e.g. the detection rate may decrease significantly. A pavement marking tape that includes radar reflective structures according to this disclosure may provide a redundant and more precise lane detection method. A PAAV may more accurately detect the vehicle pathway based on a radar return signal received from the pathway article, which may increase vehicle and passenger safety.

Examples in which the radar reflective structures of this disclosure are combined with other sensable elements may provide additional advantages over other types of pathway articles. For example, pavement marking tapes comprising these radar reflective structures and at least one additional sensable feature that may be detected by other sensor systems mounted on the automobile, such as magnetic detectors, to provide additional redundancy in a compact planar structure. In some examples, the radar reflective structures and the additional sensable feature may be located in the same region of the marking tape or adjacent to each other. In other words, the redundancy in the detectable features of the marking tape may enable use of sensor fusion to provide greater confidence of detection of the pavement marking under a wider range of conditions and to enable distinction between pavement marking and other radar- reflective objects in the field of view.

To simplify the explanation, the description in this disclosure may focus on the example of a pathway article on a pathway with the radar transceiver on the vehicle. However, the radar reflecting structures of this disclosure may equally apply in examples in which the radar reflecting structure are in a compact planar structure affixed to a vehicle, such as a license plate, a decal, or similar article. In some examples a radar transceiver may be stationary along the vehicle pathway and transmit incident radar radiation toward a vehicle and receive reflected radar radiation from the radar reflecting structure on the vehicle. In other examples, a first vehicle may transmit radar radiation toward a second vehicle and receive reflected radar radiation from the radar reflecting structure on the second vehicle.

The radar reflective structures in a compact planar structure according to the techniques of this disclosure differ from other types of radar-reflective pavement markers. For example, the radar reflective structures of this disclosure and the compact planar structure may have advantages over cat’s eye pavement markers, because of lower cost, ease of maintenance and pavement marking tape may be more applicable in areas subject to snowfall and the use of snowplows than cat’s eye type pavement markers.

The radar reflective structures of this disclosure may also have advantages over frequency selective surfaces. For example, the radar reflecting structures of this disclosure have may broader range of detection distance, when compared to other structures. Also, periodic placement and angular directionality may enable the radar signal transmitter to be at least one pulsed signal transmitter on one or both sides of a PAAV. By placing a marking tape of this disclosure on either side of a vehicle pathway may protect marking tape from abrasion, wear, fouling, plasticization from oil and grease on roadway that may deleteriously affect the modulus of marking tape. In examples of a marking tape with a low RCS compared to the marking tape of this disclosure, the low RCS marking tape may have to be placed on a pathway somewhere under the vehicle. Therefore, the wear, soiling and damage of a low RCS marking tape may limit the durability of other sensible features than would otherwise enable redundancy via sensor fusion.

FIGS. 2A-2D are conceptual diagrams illustrating top views of example arrangements of radar reflecting structures within pathway articles, according to one or more techniques of this disclosure.

FIGS. 2A-2D illustrate example respective pathway articles 232A-232D (collectively, pathway articles 232”), which may correspond to any of pathway articles 132 of FIG. 1. Pathway articles 232 illustrated in FIGS. 2A-2D are only examples and other pathway articles 232 may exist.

Each pathway article of pathway articles 232 include a plurality of edges 240, 242, 244, and 246. In some examples, edges 240, 242 may be referred to as long edges or long axis and edges 244, 246 may be referred to as short edges or short axis. For example, pathway articles 232 may be relatively longer than they are wide. For instance, pathway articles 232 may be pavement marking tapes that indicate a boundary of one or more lanes of traffic, and may be defined by a width on the order of several inches (e.g., approximately 4 inches, or approximately 10 centimeters) and a length on the order of yards (or meters), tens or hundreds of yards (or meters), miles (or kilometers), or longer.

As illustrated in FIG. 2A, pathway article 232A includes a plurality of radar reflecting structures 234A_I-234A_N (collectively,“radar reflecting structures 234A”). Each of radar reflecting structures 234A include a plurality of antennas. For example, radar reflecting structure 234Ai includes antennas 236A_l; 236A₂, 236A₃ and 236A4 (collectively,“antennas 236A”).

In some examples, each radar reflecting structure of radar reflecting structures 234A may be orientated in the same or similar direction. For examples, as illustrated in FIG. 2A, each of radar reflecting structures 234A are orientated such that the lateral members 238, 239 of antennas 236 are substantially parallel to edges 244, 246 of pathway article 232. Similarly, each of radar reflecting structures 234A may be orientated such that each antenna 236 is substantially parallel to edges 240, 242 of pathway article 232. For instance, radar reflecting structures 234A may be squared with pathway article 232A. In some examples, orientating radar reflecting structures 234A square with pathway article 232A may enable a radar equipped vehicle (e.g., PAAV 110 of FIG. 1) to detect pathway articles adjacent (e.g., directly adjacent) to vehicle 110 using radar devices that are orthogonal to the direction of travel of vehicle 110.

As illustrated in FIG. 2B, pathway article 232B includes a plurality of radar reflecting structures 234B_I-234B_N (collectively,“radar reflecting structures 234B”). Each of radar reflecting structures 234B include a plurality of antennas similar to antennas 236A of FIG. 2A. As illustrated in FIG. 2B, each of radar reflecting structures 234B are orientated in a same or similar direction (e.g., within a threshold number of degrees, which may be defined by a manufacturing tolerance) as one another. As further illustrated in FIG. 2B, each radar reflecting structure of radar reflecting structures 234B is angled relative to pathway article 232B. In other words, of radar reflecting structures 234B are not squared to pathway article 232B. Orientating radar reflecting structures 234B as shown in FIG. 2B may enable radar reflecting structures 234B to receive incident radar radiation from, and redirect the radar radiation back to, directions that are not orthogonal to edges 240, 242 of pathway article 232B. In this way, radar reflecting structures 234B may enable a radar equipped vehicle (e.g., PAAV 110 of FIG. 1) to detect pathway articles ahead of or behind vehicle 110 using radar devices that directed within a threshold number of degrees (e.g., between approximately 30 and approximately 60 degrees) relative to the direction of travel of vehicle 110.

As illustrated in FIG. 2C, pathway article 232C includes a plurality of radar reflecting structures 234C_I-234C_N (collectively,“radar reflecting structures 234C”). Each of radar reflecting structures 234C include a plurality of antennas similar to antennas 236A of FIG. 2A.

Radar reflecting structures 234C may be orientated in different directions. For example, as illustrated in FIG. 2C, radar reflecting structure 234Ci is orientated in a first direction and radar reflecting structure 234C₂ is orientated in a different direction. In some examples, radar reflecting structures 234C may be orientated in alternating directions. For example, radar reflecting structure 234Ci may be orientated in a first direction and radar reflecting structure 234C₂ may be orientated 180 degrees opposite the orientation of radar reflecting structure 234Ci. In some examples, orientating radar reflecting structures 234C as shown in FIG. 2C may enable radar reflecting structures 234C to receive incident radar radiation from different directions, and redirect the radar radiation back to the respective direction from which the radiation was received. For instance, pathway article 232C may include a pavement marking tape dividing traffic traveling in opposite directions (e.g., such as pathway article 132B of FIG. 1) and may enable a single pathway article to reflect radar radiation to vehicles on opposite sides of a road. In this way, radar reflecting structures 234C may enable different radar equipped vehicles (e.g., PAAV 110 of FIG. 1) that are traveling in opposite directions to detect the same pathway article 232C.

As illustrated in FIG. 2D, pathway article 232D includes a plurality of radar reflecting structures 234D_I-234D_N (collectively,“radar reflecting structures 234D”). Each of radar reflecting structures 234D include a plurality of antennas similar to antennas 236A of FIG. 2A.

Radar reflecting structures 234D may be orientated in different directions. In some examples, radar reflecting structures 234D are orientated in a pattern. For example, as illustrated in FIG. 2D, radar reflecting structure 234Di is orientated in a first direction, radar reflecting structure 234D₂ is rotated approximately 45 degrees from radar reflecting structure 234Di, radar reflecting structure 234D₃ is rotated approximately 45 degrees from radar reflecting structure 234D₂, and so on. In some examples, orientating radar reflecting structures 234D as shown in FIG. 2D may enable radar reflecting structures 234D to receive incident radar radiation from different directions, and redirect the radar radiation back to the respective direction from which the radiation was received.

In this way, radar reflecting structures 234B may enable radar equipped vehicles to detect a given pathway article at various locations from various distances, and detect the pathway article when traveling in different directions.

FIG. 3 is a conceptual diagram illustrating a top view of example arrangements of radar reflecting structures within a within pathway article, according to one or more techniques of this disclosure. As illustrated in FIG. 3, pathway article 252A includes a plurality of groupings of radar reflecting structures 254A_I-254A₄. Pathway article 252A is similar to pathway articles 232A - 232D depicted in FIGS. 2A - 2D. Each of radar reflecting structures in pathway article 252A includes a plurality of antennas similar to antennas 236A of FIG. 2A.

The groupings of radar reflecting structures may be called a radar reflective array. In some examples there may be a predetermined distance or spacing 258 between groupings of radar reflective structures in a pathway article, such as pathway article 252A. The number of radar structures and spacing may convey additional information to a PAAV. As one example, pathway article 252A may be a pavement marking tape for a lane indicator on a vehicle pathway. A PAAV traveling along a vehicle pathway may detect a pattern of an array of three radar reflective structures followed by an array of two radar reflective structure, similar to the pattern depicted by radar reflective arrays 254A1 and 254A2. However, a PAAV going in the opposite direction may only detect a pattern of two radar reflective structures, such as depicted by radar reflective array 254A3. In some examples, the PAAV may be configured to determine that the first pattern indicates the correct direction and the second pattern indicates that the PAAV is traveling in the wrong direction on the vehicle pathway. In other examples, groupings or patterns of radar reflective structures may convey other information to a PAAV.

This separation between periodic arrays is also useful to counteract CTE effects. CTE is be a percentage of expansion over a baseline distance. If a feature is quite small, an expansion of 2% of the dimension of that feature is a relatively infinitesimal amount. If the feature is quite large, the overall expansion from edge to edge can be quite a substantial distance. Large elements, such as long antennas, i.e. long prism features, embedded in a length of the tape may buckle with expansion. Instead, using smaller elements in multiple radar reflecting structure in separated arrays of radar reflecting structure may help maintain dimensional integrity. In some examples, additional stress-relieving separation between the “radar reflective structure” may help to maintain dimensional integrity of the radar reflecting structures.

In some examples the spacing may be affected by the coefficient of thermal expansion (CTE) of the material of the pathway article. In some examples, the PAAV may be configured to detect changes in the reflected radar radiation caused by changes in spacing between slots. In some examples, the PAAV may be able to determine a temperature of the pathway article based on determining changes in the spacing between the slots.

FIG. 4 is a conceptual diagram illustrating an example marking tape and an example vehicle equipped with radar devices according to one or more techniques of this disclosure. Even with advances in autonomous driving technology, infrastructure, including vehicle roadways, may have a long transition period during which fully autonomous vehicles, vehicles equipped with ADAS, as well as traditional fully human operated vehicles share the road. Some practical constraints may make this transition period decades long, such as the service life of vehicles currently on the road, the capital invested in current infrastructure and the cost of replacement, and the time to manufacture, distribute, and install fully autonomous vehicles and infrastructure.

Autonomous vehicles and ADAS, which may be referred to as semi-autonomous vehicles, may use various sensors to perceive the environment, infrastructure, and other objects around the vehicle. These various sensors combined with onboard computer processing may allow the automated system to perceive complex information and respond to it more quickly than a human driver. As mentioned above, some examples of PAAVs may include the fully autonomous vehicles, as well UAVs, human flight transport devices, underground pit mining ore carrying vehicles, forklifts, factory part or tool transport vehicles, ships and other watercraft and similar vehicles. A vehicle pathway may be a road, highway, a warehouse aisle, factory floor or a pathway not connected to the earth’s surface.

FIG. 4 depicts pathway article 210 and PAAV 200, which is equipped with one or more sensors including longer range radars (LRR) 202A and 202B, medium range radars (MRR) 204A and 204B and short range radars (SRR) 206A and 206B. PAAV 200 may also include other sensors, such as cameras, as described above in relation to FIG. 1. The radar system configuration of PAAV 200 depicted in FIG. 4 is just one example for illustration. In other examples, PAAV 200 may be equipped with additional, or fewer, radar systems and arranged in other configurations. To simplify the description of FIG. 4, PAAV 200 will be described as a roadway vehicle, such as an automobile, traveling along a roadway. However, in other examples, PAAV 200 may be other types of vehicles traveling on other types of pathways, as described above in relation to FIG. 1.

LRR 202A and LRR202B may be radar systems with a field of regard (FOR) in the direction of travel of PAAV 200 and used to detect and/or track objects ahead of and behind PAAV 200. In the example of FIG. 4, the FOR of LRR 202A is the region facing forward of PAAV 200 and LRR 202B is the region facing behind PAAV 200. In some examples, LRR 202A and LRR 202B are narrowband systems in the 24 GHz or 76 GHz bands. In other examples, LRR 202A and LRR 202B may be broadband systems in the 77 GHz band.

Narrowband systems in the 24 GHz and 76 GHz bands may be used for applications such as adaptive cruise control and blind spot monitoring. A broadband radar system, for example with a bandwidth of 4 GHz, may be also used for adaptive cruise control, blind spot monitoring and obstacle or pathway detection. A broader bandwidth may enable higher spatial resolution of the radar system, relative to a unit based on 77 GHz, for example, with a 200 MHz bandwidth, which limits resolution to one meter (1 m). Higher frequency devices, such as in the 79 GHz range, may enable miniaturization of the radar unit due to physical requirements on antenna size, and also produce a lower emission power, which has the added benefit of mitigating the risk of mutual interference from units on the same roadway. Examples of units in the range of 79 GHz may be useful for short-range and medium-range applications where distinguishing potential obstacles on a vehicle pathway may be valuable.

MRR 204A and MRR 204B may have a wider azimuth FOR toward the front and rear of PAAV 200, when compared to LRR 202A and LRR 202B. In some examples, the only overlap between the MRR and LRR systems is facing forward between 76-77 GHz. To account for that overlap, in some examples may be to have the LRR 202A - 202B at 77 GHz unit have two polarizations, so that it could be distinguished from a signal generated by a MRR unit at 79 GHz. To account for that overlap, in some examples LRR 202A - 202B may have a different polarization, so that the LRR may be distinguished from a signal generated by a MRR unit. For example, a radar transmitter may transmit radar signals with transverse magnetic (TM) polarization or with transverse electric (TE) polarization. TE modes have the electric field transverse to the direction of propagation. TM modes have the magnetic field transverse to the direction of propagation.

SRR 206A and 206B may include an FOR to the right and left of the vehicle. Some applications for SRR 206A and SRR 206B may include imminent collision warning, for example to trigger air bags, as well as blind spot monitoring.

Pathway article 210, in the example of FIG. 4 may be a pavement marking tape or a tape attached to a barrier, such as a guardrail. Pathway article 210 includes radar reflective structure 212, radar reflective structure 214 and radar reflective structure 216. Each radar reflective structure 212 - 216 is at a different angle relative to the long axis 211 of pathway article 210. In contrast to radar-reflective pavement markers based on cat’s eye pavement markers and frequency selective surfaces, the radar reflective structures according to the techniques of this disclosure are in a compact planar structure. The compact planar structure may provide advantages over other types of roadway, for example that radar reflective structures of this disclosure may be included in marking tape that may be applied to pavement or other pathway structures.

As described above in relation to FIGS. 1 - 3, the reflected radar radiation from the radar reflective structure 212 - 216 may be at a maximum when the lateral member or lateral portion of the radar reflective structure is substantially orthogonal to the incident radar radiation. For example, radar reflective structure 220 is at an angle 212 that is parallel to long axis 211 of pathway article 210. In this orientation, radar reflective structure 220 is approximately orthogonal to the incident radar radiation from SRR 206B when PAAV 200 is approximately adjacent to radar reflective structure 220.

In another example, when PAAV 200 moves to be adjacent to radar reflective structure 224, which is at angle 216 relative to long axis 204, radar reflective structure 224 would not be orthogonal to the incident radar radiation from SRR 206B. Therefore, SRR 206B may receive less reflected radiation from radar reflective structure 224 when PAAV 200 is adjacent to radar reflective structure 224.

Similarly, SRR 206B may receive less reflected radar radiation when adjacent to radar reflective structure 222 at angle 214 relative to long axis 211. In contrast, the incident radar radiation from MRR 204A and LRR 202A may be orthogonal to radar reflective structure 222 or radar reflective structure 224 when PAAV 200 is at some distance from radar reflective structure 222 or radar reflective structure 224.

Therefore, MRR 204A and LRR 202A may receive a more reflected radiation from radar reflective structure 222 or radar reflective structure 224 when PAAV 200 is at some distance from radar reflective structure 222 or radar reflective structure 224.

In this manner, by selecting the angle of a radar reflective structure relative to the long axis of pathway article 210, and therefore relative to the position of PAAV 200, the radar reflective structure of this disclosure may be adapted to a variety of functions. As one example, radar reflective structure 220 at angle 212 may be used in a lane guidance function, in addition to any lane guidance function from a visual or other type of camera. The lane guidance function from multiple sources may be used as a cross check by computing device 40 depicted in FIG. 1. In other examples, such as if the lane markings are obscured by low visibility radar reflective structure 220 may provide a more accurate lane guidance function than can be provided by a visual camera under these conditions. Similarly, radar reflective structure 224 may be used to provide forewarning of an upcoming curve or lane shift based on the reflected radiation from MRR 204A and LRR 202A.

One example of a radar reflecting structure is a resonant structure, such as an array of antennas with dimensions that are a function of the expected frequency. For example, an array of antennas with a length that is one-half the wavelength of the expected frequency. A resonant structure type of radar reflecting structure may have the advantage of increasing the directivity of the backscattered radar signal because the elements of a resonant type of radar reflecting structure may be designed to eliminate unwanted scattering directions. However, the bandwidth for a resonant type radar reflecting structure may be limited to the bandwidth of the resonating element. The length of the resonating element may be tuned to a desired frequency band, such as a length of one-half wavelength. In the example of a half wavelength dipole, the RCS may be maximized at resonance. Therefore, wider bandwidth radar systems may get less efficient backscatter, i.e. a smaller RCS, as the frequency of the radar signal differs from the bandwidth of the resonating element. Also, the resonance frequency of a resonant structure type may be influenced by material surrounding the structure, which may be difficult to control.

In contrast, non-resonant structures may be very small size compared to the radar signal wavelength such that each element exhibits an omni-directional diffraction pattern. Therefore, non resonant RCS structures may not suffer from“out-tuning” issues. Some examples of non-resonating elements may include strips or slots with extremely small height (sub-millimeter). Other advantages of non-resonant structures may also include that RCS is less sensitive to manufacturing tolerance and electromagnetic loading by nearby objects which may results in change of electrical length of the elements. This is because the non-resonant structure may be less dependent on the dimensions of the elements. Also, the RCS of a radar reflecting structure of this disclosure may be larger due to the fact that the radiating elements are not limited to the resonant length. Because spacing is tied to frequency, a radar reflecting structure may exhibit larger RCS over a wider range of frequencies by using“non-uniform” spacing. In other words, if a large array of radar reflecting structures includes smaller sub-arrays, each with different spacing to cover adjacent frequency bands, overall bandwidth may be widened without having to change the dimensions of each element.

Material of the radar reflecting structure of this disclosure may be metallic, conductive, ferro magnetic or a material with high dielectric properties. One example of this radar reflecting structure is a flexible construction with this geometry buried beneath a layer of material with low dielectric properties in the marking tape, such as pavement marking tape described above. In some examples the radar reflecting structure s may be constructed of a molded or embossed material and coated with a metallic or other radar reflective coating. In other examples, the elements may be etched from a plate. In some examples, magnetic material, detectable by magnetic detectors, may be included in a marking tape in layers beneath the radar reflecting structure. In other words, the magnetic material may be placed so it does not interfere with the radar reflective properties of the radar reflecting structures.

FIGS. 5A - 5B are conceptual diagrams illustrating an example resonant radar reflecting structures according to one or more techniques of this disclosure. FIG. 5 A illustrates an example marking tape 300 that includes a plurality of antenna in radar reflecting structures, such as radar reflecting structure 302. Pathway article 300 is similar to pathway articles 232A - 232D depicted in FIGS. 2A - 2D, as well as pathway article 252A depicted in FIG. 3. Each of radar reflecting structures in pathway article 300 includes a plurality of antennas similar to antennas 236A of FIG. 2A. The antennas of radar reflecting structure 302 take the form of resonant conductive strips, or slots in a conductive material. For clarity and simplicity, the description of FIGS. 5A and 5B may focus on conductive strips, but the descriptions and properties may apply equally to slots in conducive material, unless otherwise noted.

The radar reflecting structure 301 of FIG. 5B comprises periodic array of elements, which act as antennas, arranged in manner to backscatter incident radar radiation, back in the direction in which it was incident upon the array, or some other direction. The dimensions, spacing and expected incident angle of incident determines the angle of reflected radiation. Radar radiation may also be referred to as electromagnetic radiation in this disclosure.

In some examples, the antennas 304 A - 304N are slots in a conductive layer or conductive sheet 306. Some examples of conductive layers may include bulk metal, foils, and conductive coatings. Either the conductive strips, or the conductive layer may be coated with vapor-coated metal, electroplated metal, electroless plated metal, molded graphene sheet, composite coating comprising enough conductive carbon black to have substantial surface conductivity. In some examples, the radar reflecting structure may be coated with a coating that presents a large difference in dielectric constant relative to air. In some examples the slot-type antennas may be etched from a solid plate of conductive material such as metal.

In other examples, antennas 304A - 304N are rows of conductive strips that may be placed on, or embedded in, a non-conductive dielectric layer or sheet 306. The conductive strip antennas may be copper or other metal material etched on non-conducting substrate, sheet 306, or any metal or conductive material deposited via masked vapor deposition, microcontact printing, conductive ink or other suitable processes onto a non-conducting substrate in a pattern as depicted in the example of FIG 5B.

Each respective antenna, such as antenna 304A may have a length (L) 310 and a width (W) 314 and may be spaced from other antennas in a respective column 303 of antennas by spacing (D) 312. In some examples, length (L) 310 of the antennas may be one-half the wavelength of the expected incident radar radiation, or some integer multiple of the half wavelength. For example, for an expected incident radar radiation of 79 GHz, the wavelength, l = 149 mils or 3.8 mm. Therefore, the length (L) 310 may be set to approximately l/2 = 74.5 mils or 1.9 mm.

Antennas 304A - 304N are in a column 303. Radar reflecting structure 301 depicts seven rows 305 of antenna columns 303. In other examples, a radar reflecting structure may include more or fewer rows of antenna columns 303. In general, a larger number of columns 303 and rows 305 that interact with an incident radar radiation, the more electromagnetic energy may be reflected. The practical limits on the number of columns 303 and rows 305 depend on the width of the pathway article, such as a marking tape, the angle of radar reflecting structure 301 relative to the long axis of the marking tape, the spacing (D)

312, the length (L) 310 and other dimensions of antennas 304A - 304N, and the beamwidth of the incident radar radiation.

The width (W) 314 and spacing (D) 312 may be set according to the desired backscatter direction and expected frequency and expected incident angle of the incident radar radiation. For a uniformly excited, equally spaced linear array of N antenna elements, the normalized array factor can be expressed according to:

Where y = b d cos Q + a, and

b : Phase constant

d: Element spacing Q : Angle with respect to array axis

a: Phase progression of exciting current.

The array factor is a sine function. It has a peak at xp = 0 which determines the main beam and repeats with period of 2p. One can also determine the visible range of the antenna according to bά and a values. Since the xp expression represents the points on a circle whose radius is bά and centered at a, an straightforward way to estimate the polar radiation (or scattering) pattern of the array factor is to make a nonlinear graphical transformation from xp values to polar Q values (pictured above). Each Cartesian xp value corresponds to a polar Q value where the vertical line crosses the circle. As can be seen from the picture, the array factor can be engineered to exhibit desired pattern by moving the visible region to the right or left by changing bά and a values. An N element array has N-l nulls and N-2 side lobes at each period.

In the example of FIGS. 5A and 5B, a plane wave of incident radar radiation strikes a planar scatterer, such as radar reflecting structure 301 with an incident angle of 6_inc with respect to the scatterer plane. For a first goal, configure the dimensions of radar reflecting structure 301 to backscatter the incident radar radiation with a main beam of the reflected radar radiation at Q = 180° . For a scattering problem with plane wave excitation, the phase progression can be written according to: a = b d cos 9_inc. To create a main beam at Q = 180°, map the right boundary of the visible region to xp = 2p. hence:

b d + b d cos 9_inc = 2p

Which can be simplified to the below equation, which gives the spacing (d) 312 between antenna elements:

d 1

l 1 + cos 9_inc

To increase backscattered power, reduce the boresight (Q = 0) radiation. Therefore, map the left

2n

boundary of the visible region into the lst null of the array factor, i. e. xp =— , which results in

Replacing A gives:

Therefore, to achieve the first goal of create a main beam at Q = 180°, set the dimensions of the array of rows 305 and columns 303 such that:

spacing elements

The design guidelines above may apply to an array factor pattern. Elements are assumed isotropic and may be replaced with actual scatterers (antennas). The final RCS pattern may be based on the array factor and single scatterer (antenna) pattern. Therefore, the choice of a desirable antenna may be such that the antenna does not present a null at desired angle, because a null will override the array factor. In some examples choices of elements may include: dipole, slot, and patch scatterers (antennas).

As a second goal, configure the dimensions of radar reflecting structure 301 such that the main beam of the reflected radar radiation is substantially opposite the direction of the incident radar radiation (i.e. Q =—0_inc). To create a main beam at Q =—Q_inc. we shall move the visible region to the right such that the maximum of array factor (xp = 2p) corresponds to the polar point of b d cos 9_inc, hence:

b d cos 6_inc + b d cos 6_inc = 2p

Which can be rewritten as:

2b d cos 9_inc = 2p

Then the spacing can be calculated according to:

d _ 1

2 2 cos Q i_nc

and the number of elements may be determined according to:

2 COS Oi-nr

N = -

1 cos di_nc

Therefore, for the second goal ing and number of elements may follow:

spacing elements

i_nc

In some examples, to remove the transmission and image components a radar reflecting structure may include a grounded film.

In some examples, as for the second goal described above, the periodic array of antennas of the radar reflecting structure 301 may be configured to be retroreflective, that is to reflect the incident radar radiation back in the same direction from which it came. In the example of a pavement marking tape, the angle of incidence, or entrance angle, of the incident radar radiation may be low, compared to the surface of the pavement marking tape. The antennas may be configured to create a large RCS for radar reflecting structure 301 based on a low entrance angle. In other examples, such as on some pathway articles, such as a barrier, or a license plate on a vehicle, the expected angle of incidence for the incident radar radiation may be high, i.e. have a high entrance angle. The dimensions and spacing for the antennas 304A - 304N, may be configured to create a large RCS for radar reflecting structure 301 based on a high entrance angle.

FIGS. 6A - 6C are conceptual diagrams illustrating an example resonant radar reflecting structures with a radius according to one or more techniques of this disclosure. FIG. 6A illustrates an example marking tape 330 that includes a plurality of radar reflecting structures, such as radar reflecting structure 332. Pathway article 330 is similar to pathway articles 232A - 232D depicted in FIGS. 2A - 2D, as well as pathway article 252A depicted in FIG. 3. Similar to the antennas described above in relation to FIGS. 5A and 5B, the antennas of radar reflecting structure 332 take the form of resonant conductive strips, or slots in a conductive material. In some examples, the curvature may cause a more focused beam of reflected radar radiation in the focal direction, when compared to a straight element. Similar to radar reflecting structure 301 described above in relation to FIG. 5B, the radar reflecting structure of FIG. 6B comprises periodic array of elements, which act as antennas, arranged in manner to backscatter incident radar radiation. As with radar reflecting structure 301, in some examples, the antennas 334A - 334N are slots in a conductive layer similar to conductive sheet 306 depicted in FIG. 5B.

In other examples, antennas 334A - 334N are rows of conductive strips that may be placed on, or embedded in, a non-conductive dielectric layer or sheet 306. The conductive strip antennas may be copper or other metal material etched on non-conducting substrate, or any metal or conductive material deposited via masked vapor deposition, microcontact printing, conductive ink or other suitable processes onto a non-conducting substrate in a pattern similar to the example depicted by FIG 5B.

Each respective antenna, such as antenna 304A may have a length (L) 340, as shown in FIG. 6C, and a width (W) 344 and may be spaced from other antennas by spacing (D) 342. In the example of FIG. 6B, antennas may also include a radius (R) 348. Radius (R) 348 may provide improved performance, in some examples, such as by causing a more focused main beam of reflected radar radiation.

In the example of FIGS. 5B - 6C, all the dimensions of the antenna are the substantially the same. In other examples, a radar reflecting structure may include antennas of different dimensions, for example, to account for a broader bandwidth of expected frequencies of the incident radar radiation, or a wider variation in expected angle of incidence.

FIG. 7 is a diagram illustrating a detailed view of the slot radar reflecting structure according to one or more techniques of this disclosure. The example of FIG. 7 illustrates the impact of radius that form the walls of the slot type antennas of this disclosure. In some examples the slot type antennas may be referred to as apertures in a conductive sheet.

Conductive sheet 350 includes three resonant or non-resonant slot antennas 352A - 352C, as described above in relation to FIGS. 5A - 6C. Slot antenna 352C is cross-sectioned by A-A, as shown.

FIG. 7B illustrates the cross section of an example slot antenna, such as slot antenna 352C. The comers 354 of the walls that form the slots may reflect more of the incident radar radiation when the comers 354 have a small radius. In other words, when comer 354 is substantially a right angle between the horizontal and vertical surfaces that form slot antenna 352C, then slot antenna 352C may reflect more incident radar radiation compared to a more rounded comer. Therefore, when the comers of the surfaces that form slot antennas 352A - 352C have a larger radius, the periodic array of reflective elements that make up the radar reflecting stmcture in conducting sheet 350 may be less effective at reflecting the incident radar radiation. Said another way, when the comers that form the slot antennas are substantially at right angles, then the RCS of the radar reflecting stmcture that includes slot type antennas may be larger. Sharp-edged comers for slot type antennas may be more desirable than comers that are more rounded, with a larger radius.

FIGS. 8 A - 8B are conceptual diagrams illustrating an example non-resonant radar reflecting structures according to one or more techniques of this disclosure. FIG. 8 A illustrates an example marking tape 370 that includes a plurality of antenna in radar reflecting structures, such as radar reflecting structure 372. Pathway article 370 is similar to pathway articles 232A - 232D depicted in FIGS. 2A

2D, as well as pathway article 252A depicted in FIG. 3. Each of radar reflecting structures in pathway article 370 includes a plurality of antennas similar to antennas 236A of FIG. 2A. The antennas of radar reflecting structure 372 take the form of non-resonant conductive strips, or non-resonant slots.

Similar to radar reflecting structure 301 depicted in FIG. 5B, radar reflecting structure 371 comprises periodic array of elements, which act as non-resonant antennas, arranged in manner to backscatter incident radar radiation for example back in the direction in which it was incident upon the array, or some other direction. The dimensions, spacing and expected incident angle of incident determines the angle of reflected radiation.

Similar to antennas 304A - 304N depicted in FIG. 5B, in some examples, antennas 374A - 374N are slots in a conductive layer or conductive sheet 375. Some examples of conductive layers may include bulk metal, foils, and conductive coatings. In other examples, antennas 374A - 374N are rows of conductive strips that may be placed on, or embedded in, a non-conductive dielectric layer or sheet 375. The conductive strip antennas may be copper or other metal material etched on non-conducting substrate, sheet 375, or any metal or conductive material deposited via masked vapor deposition, microcontact printing, conductive ink or other suitable processes onto a non-conducting substrate in a pattern as depicted in the example of FIG 8B.

Each respective antenna, such as antenna 374A, may have a length (L) 380 and a width (W) 376 and may be spaced from other antennas by spacing (D) 378. In some examples width (W) 376 may be approximately 0.2 mm. Unlike the example of FIG. 5B, length 380 may not be based on the wavelength of the expected incident radar radiation. In general, increasing the length may increase the amount of reflected radar radiation backscattered toward the radar receiver. As noted above in relation to FIG. 5B, length 380, and other dimensions of radar reflecting structure 371 may have practical limits that depend on the width of the pathway article, such as a marking tape, the angle of radar reflecting structure 371 relative to the long axis of the marking tape, the spacing (D) 378, and the beamwidth of the incident radar radiation.

The dimensions for a non-resonant radar reflecting structure may be determined in a similar manner to that described above for resonant radar reflecting structure described above in relation to FIG. 5B. For a periodic arrangement to be retro-reflective, the element spacing and number is determined by the following expressions:

For small angle of incidences (Oi < 5o), Cos(Oi) will be close to 1, and above formulas can be approximated as:

Any type of scatterer may be used to back-scatter the incident wave. Scattering efficiency depends on the material, number of elements, and similar factors, as described above. Non-resonant structures may be very small size compared to wavelength such that each element exhibits an omni-directional diffraction pattern. The example of FIGS 8A - 8B depict non-resonating etched slots on a metallic ground plane or conductive strips on a non-conductive layer with a length (L) 380 depending on how large of a backscattering level desired. As described above in relation to FIG. 5B, adding a ground plane on the opposite side of the radar reflecting structure from the incident radar radiation may increase the amount of radiation reflected to the radar transceiver, i.e. a larger backscattering level. In the example of slots type antennas, transmitted power through the open slots may bounce back from the ground plane resulting in the larger backscattering level.

FIGS. 9A - 9B are conceptual diagrams illustrating an example non-resonant radar reflecting structures with a radius according to one or more techniques of this disclosure. FIG. 9A illustrates an example marking tape 380 that includes a plurality of antenna in radar reflecting structures, such as radar reflecting structure 382. Pathway article 380 is similar to pathway articles 232A - 232D depicted in FIGS. 2A - 2D, as well as pathway article 252A depicted in FIG. 3. Each of radar reflecting structures in pathway article 380 includes a plurality of antennas similar to antennas 236A of FIG. 2A. The antennas 384A - 384N of radar reflecting structure 382 take the form of non-resonant conductive strips or non resonant slots with a radius or curvature, similar to antenna 334A - 334N depicted in FIG. 6B.

Similar to radar reflecting structure 301 depicted in FIG. 5B and radar reflecting structure 371 depicted in FIG. 8B, radar reflecting structure 371 comprises periodic array of elements, which act as non-resonant antennas, arranged in manner to backscatter incident radar radiation for example back in the direction in which it was incident upon the array, or some other direction. The dimensions, radius, spacing and expected incident angle of incident determines the angle of reflected radiation.

Each respective antenna, such as antenna 384A, may have a length (L) 390 and a width (W) 396, have a radius (R) 394, and may be spaced from other antennas by spacing (D) 398. In some examples width (W) 376 may be approximately 0.2 mm. Unlike the example of FIG. 5B, length 380 may not be based on the wavelength of the expected incident radar radiation. In general, increasing the length may increase the amount of reflected radar radiation backscattered toward the radar receiver. The radius may impact the focus of the main beam of the reflected radar radiation. As one example, antennas 384A - 384N with an arc of 10 degrees for a radius of 5 feet may give the radar reflecting structure a focal point of 5 feet. As noted above in relation to FIG. 5B, length 380, and other dimensions of radar reflecting structure 381 may have practical limits that depend on the width of the pathway article, such as a marking tape, the angle of radar reflecting structure 381 relative to the long axis of the marking tape, the spacing (D) 398, and the beamwidth of the incident radar radiation. In one example, the slots have an arc of 10 degrees for a radius of 5 feet which gives the structure a focal point of 5 feet.

The radar reflecting structures of this disclosure, such as those depicted in the examples of FIGS. 5A - 9B, employ appropriately spaced elements to create a diffracted beam of reflected radar radiation. In some examples the beam may be reflected back in the direction of the incident radar beam. Each element, or antenna, scatters some of the incident electromagnetic wave. By appropriately spacing the elements, the scattered energy can be made to add up in a specific direction, as described above in relation to FIG. 5C., such back towards the radar transmitter. In other examples, the elements of a radar reflecting structure may cause the radar radiation to scatter by various mechanisms. In some examples, elements may be made of conducting materials, in which case, currents induced on the element by the incident radar radiation may re-radiate to create the scattered signal. In other examples, elements may also be physical structures which have material electrical properties, i.e., permittivity and/or permeability, that are different from those of other the materials in the vicinity of the elements. In this case, it is the abrupt change in electrical properties that creates scattering of the incident signal. For example, the material may have a high dielectric constant when compared to the surrounding air. In this disclosure, the term permeability refers to a quantity measuring the influence of a substance on the magnetic flux in the region it occupies. Permittivity refers to the ability of a substance to store electrical energy in an electric field. Dielectric strength refers to the ability of an insulating material of a specified thickness to withstand high voltages, i.e. an electric field, without breaking down. In other words, a high dielectric material can withstand a relatively higher voltage without breaking down, i.e. without experiencing failure of its insulating properties compared to a lower dielectric material.

FIG. 10 is a diagram illustrating a side view of an example reflection and scattering of a radar beam with a radar reflective structure of this disclosure. FIG. 10 illustrates a cross sectional view of a radar reflective structure 700A with 0 = 0 (theta = 0) indicating the angle orthogonal to antenna of the radar reflective structure. To simplify the description, the radar reflective structure will be described in terms of a radar reflective structure that is part of a pavement marking tape. Therefore, 0 = 0 indicates a direction straight up and + 90 and - 90 indicating directions along the pavement surface.

Incident radar radiation 701 strikes radar reflective structure 700A resulting in a reflected radar radiation 704 with 3 dB vertical beamwidth 706 as well as backscatter 702. Radar reflective structure 700A may include any one or more radar reflective structures, such as described above in relation to FIGS. 5A - 8B.

As described above, the type of radar reflective structure, as well as the length, number of structures, material, spacing and other properties of radar reflective structure 700A may determine the beamwidth of reflected radar radiation 704, the amount of energy that is reflected and in the backscatter 702 and the direction of reflected radar radiation 704. Also, in the example of slots, as described above in relation to FIGS. 7A and 7B, the“sharpness” of the slot edges may also impact the amount of reflected radar radiation. For example, increasing the lateral length of each antennas of radar reflective structure 700A may have little impact on 3dB vertical beamwidth 706, i.e. the angular position of the 3dB boundary of reflected radar radiation 704 as well as little impact on the energy lost to backscatter 702 and sidelobes. However, increasing the lateral length may increase the energy in reflected radar radiation 704. Increasing the number of radar reflective structures in radar reflective structure 700A may increase the magnitude of the main lobe of reflected radar radiation 704 as well as decrease the 3dB vertical beamwidth 706. For example, a radar reflective structure with 100 reflective elements, or antennas, may have an increased magnitude of a main lobe when compared to a radar reflective structure with twenty- five elements. The number of radar reflective structures in an array may be limited by the angle of the radar reflective structure relative to the long axis of the pathway article, as well as the dimensions of the pathway article and spacing between radar reflective structures as needed for the expected frequency of the incident radar radiation.

In some examples, radar reflecting structure 700A may include a conducting groundplane below the reflective elements, as described above, for example in relation to FIGS. 5B and 8B. The groundplane may be separated from the reflective elements by a dielectric substrate. The addition of a groundplane at a predetermined distance below the reflective elements of radar reflecting structure 700A may increase reflected energy in reflected radar radiation 704 by hindering incident radar radiation from passing through the slots into the ground. The added groundplane may also de-couples radar reflecting structure 700A electromagnetically from the ground materials.

FIG. 11 is a diagram illustrating a top view of an example reflection and scattering of a radar beam with a radar reflective structure of this disclosure. FIG. 11 is the top view example of similar radar reflective structure 700B that is similar to radar reflective structure 700A and may receive incident radar radiation similar to incident radar radiation 701 described above in relation to FIG. 10.

Radar reflective structure 700B includes a plurality of radar reflective structures with lateral length 720. The principles in the description of FIG. 11 apply also to radar reflective structures with radar reflective structures described above in relation to FIGS. 5A- 8B. Radar reflective structure 700B may reflect energy in the form of a main lobe of reflected radar radiation 714 with 3dB horizontal beamwidth indicated by 716A and 716B, as well as backscatter 712.

Similar to described above, increasing lateral length 720 of each antenna of radar reflective structure 700B may increase the magnitude of the main lobe of reflected radar radiation 714 and decrease the amount of energy lost to backscatter 712 and sidelobes. Increasing lateral length 720 may also decrease the 3dB horizonal beam width of reflected radar radiation 714. Increasing the number of radar reflective structures in radar reflective structure 700B may increase the magnitude of the main lobe of reflected radar radiation 714 but have less impact on the 3dB horizontal beamwidth or the energy lost to backscatter 712 and sidelobes. For example, doubling the number of radar reflective structures may increase the main lobe energy by four times, but have little effect on the horizontal beamwidth.

Increasing the number of radar reflective structures by five times can cause a significant increase in the main lobe magnitude of reflected radar radiation 714 as well as reduce the 3dB horizontal beam width.

As mentioned above in relation to FIG. 10 above, the number of radar reflective structures may be limited by the dimensions of the pathway article.

FIG. 12 is a block diagram illustrating an example compact planar structure that includes a radar reflective structure according to one or more techniques of this disclosure. Compact planar structure 900 will be described in terms of a marking tape, or pavement marking tape, but other examples, such as signs may equally apply. Compact planar structure 900 may include a backing layer 910, a radar reflective layer 908, a sensable layer 902 and one or more other layers, which may not be shown in FIG. 12. In the example of a pavement marking tape, or a marking tape to be applied to a guard rail, traffic barrel and similar pathway articles, compact planar structure 900 may include an adhesive layer 914. In some examples, one or more layers included in backing layer 910 may be referred to as a carrier film, or a continuous base sheet. Some examples of materials that may be included in one or more layers may include polyethylene terephthalate (abbreviated as PET or PETE), polyesters, acrylics, rubbers, thermoplastics, polyolefins and similar materials.

In some examples, a marking tape comprising compact planar structure 900 may be used as a pavement marking for marking lanes, centerlines, edges or other features of a vehicle pathway. The dimensions of the marking tape may conform to a standard as prescribed by the region of use. In the example of a pavement marking for marking lanes, the material may be between about 7.5 and 30 centimeters (3 and 12 inches) wide and 30 centimeters (12 inches) long or longer. In the United States, pavement marking tapes are about 4, about 6, or about 8 inches wide (10 cm - 20 cm). In Europe, pavement marking tapes are typically about 15 or 30 centimeters wide.

In other examples, a marking tape comprising compact planar structure 900 may be used as a decal, or similar structure for use indoors, such as a warehouse or factory vehicle pathway. For an indoor application, compact planar structure 900 may not include for example, a protective layer or a conformance layer. In other examples, such as a decal or license plate used on a vehicle, compact planar structure 900 may include a protective layer to prevent moisture, oil, dirt or other contaminants from affecting the sensible layer and/or radar reflective layer but may not include protection from tires nor anti skid features, for example. Similarly, marking tape for application to a rough surface, such as a concrete barrier may include a conformance layer, while a marking tape for application to a smooth surface may not include a conforming layer. In other words, the construction of compact planar structure 900 may be specific for the particular application to which a pathway article that includes compact planar structure 900 may be used.

Sensable layer 902, in the example of FIG. 12 may include a retroreflective layer 906, with reflective elements and one or more protective layers 904. As discussed above, sensable layer 902 may also include any combination of LIDAR reflective elements, UV and IR reflective elements, magnetic elements, and other similar elements that may be detectable by one or more sensors on a PAAV (not shown in FIG. 12). Examples of retroreflective layer 906 may include an exposed-lens system, an enclosed lens retroreflective sheet, encapsulated-lens, embedded lens, cube-comer type, microsphere- based retroreflective sheetings that comprise a monolayer of transparent microspheres partially embedded in a binder layer, and other types of retroreflective sheeting as well as combinations of any of the above. Retroreflective layer 906 may also include a texture to provide high retroreflectivity at both high and low light entrance angles. Sensable layer 902 is configured to allow radar signals to pass through sensable layer 902, where sensable layer 902 is placed over radar reflecting structures in radar reflective layer 908. In examples in which sensable layer 902 includes magnetic or metallic elements, the magnetic or metallic elements may be in a separate location from the radar reflecting structures of radar reflective layer 908.

Sensable layer 902 may also be colored in the visible spectrum to provide additional cues to vehicle operators or a computing device, such as computing device 40 described above in relation to FIG. 1. Some example colors may include red, yellow, white or blue. An example of an enclosed-lens retroreflective sheet that is gray colored initially, because of the aluminum reflective layer, can be changed to a desired color, for example, by adding an opaque colorant. In some examples, a combination of opaque and light transmissive colorants may be used. In this way, a pathway article that included compact planar structure 900 would have effective day and night time colors. Materials used in sensable layer 902, such as colorants, may be selected to avoid interference with the functions of the radar reflective structures in radar reflective layer 908. In some examples, an enclosed-lens retroreflective layer may not be used, and other types of non-metallic visible light retroreflective layers may be used to ensure that incident radar radiation may pass through sensable layer 902 to strike radar reflective layer 908. In other examples, visible light retroreflective portions that may include metallic elements may be placed in a separate location from the radar reflecting structures.

Backing layer 910 may include a conformance layer 912 and/or a scrim layer (not shown in FIG. 12) and adhesive layer 914. In some examples, backing layer 910 may also a scrim material to impart increased tear resistance, which allows a temporary pavement marking to be removable. Conformance layer 912 may include material such as aluminum. Backing layer 910, or other layers in compact planar structure 900 may protect a pathway article that comprises compact planar structure 900 from

deformation that may come from the effects of traffic, temperature changes and similar stresses.

Conformance layer 912 may allow a marking tape applied to a rough surface to conform and adhere to the surface, while ensuring that the rough surface does not substantially distort radar reflective layer 908 such that radar reflective layer 908 retains radar reflective properties.

Protective layer 904 may comprise a thin, high abrasion resistance and/or dirt resistant coating applied to the top surface of sensable layer 902 to protect it from traffic wear and dirt accumulation. Properties of protective layer 904 may include radar and light transmissive. In some examples, skid control particles may be partially embedded in protective layer 904, or in a layer on top of protective layer 904 (not shown in FIG. 12). Skid control particles, may be referred to as anti -skid particles, and may be included in the upper surface of a pavement marking tape to improve the traction of vehicles. In some examples, protective layer 904 may include a release liner or apply a release treatment, e.g., silicone, to the top surface. Marking tape may be wound into a roll form and the release material may make it easier to dispense the marking tape.

Protective layer 904 may be single layer or multilayer, e.g., further comprising a top film overlying underlying layers. In some examples, aliphatic polyurethanes may be used for top films because aliphatic polyurethanes properties may include clear, resistant to dirt build-up, flexible enough to conform to the road surface, bond to inorganic anti-skid particles, and resist discoloration with exposure to ultraviolet radiation. Some other examples of protective layer 904 may include, but are not limited to, ceramer coatings or crosslinked water-based polyurethane coatings. As used herein, "ceramer" refers to a fluid comprising surface-modified colloidal silica particles dispersed in a free -radically polymerizable organic liquid. Advantages of a ceramer coating may include the ability to withstand outdoor conditions with resistance to moisture, light and heat, resistance to abrasion, chemical attack and coloration by automobile engine oil. In some examples, a ceramer precursor coating composition may be applied to the surface of retroreflective layer 906, preferably including the top surface of any refracting elements and portions of backing layer 910 and radar reflective layer 908 not covered by refracting elements. The ceramer precursor composition may be cured to form sensable layer 902 with a traffic bearing, abrasion resistant, light transmissive ceramer coating.

Radar reflective layer 908 may include plurality of radar reflective structures as described above in relation to FIGS. 1 - 8B. The plurality of radar reflective structures may be arranged on radar reflective layer 908 with any combination of angles with respect to a long axis of compact planar structure 900, as well as combinations of groupings, and spacing. The combinations may also include combinations of straight and/or curved radar reflective restructures described above.

In some examples, radar reflecting layer 908 may include a conducting groundplane below the reflective elements (not shown in FIG. 12). The groundplane may be separated from the reflective elements by a dielectric substrate. The addition of a groundplane at a predetermined distance below the reflective elements of radar reflecting layer 908 may increase reflected energy in reflected radar radiation by hindering incident radar radiation from passing through the radar reflecting structure into the ground. The added groundplane may also de-couples the radar reflecting structures in radar reflective layer 908 electromagnetically from the ground materials.

Radar reflecting layer 908 may include high retroreflectivity at both high and low entrance angles. In some examples of compact planar structure 900, the spacing, or other dimensions of radar reflective structures of radar reflective structures in radar reflective layer 908 may be adjusted to account for the expected entrance angle, i.e. the radar signal angle of incidence. As described above, for example in relation to FIGS. 5 A - 5B, the spacing and other dimensions of radar reflective structures is a function of the expected radar frequency and incident radar radiation. In examples of a pathway article that includes compact planar structure 900 in some applications, the dimensions of the radar reflective structure may be adjusted depending on the application. As one example, a marking tape in an application such as a stripe on a guard rail, Jersey barrier, or wall that is parallel a first vehicle pathway and perpendicular to a second pathway that intersects the first pathway on the opposite side of the first pathway from the second pathway. In this parallel/perpendicular application, a marking tape may include radar reflective structures configured for a low entrance angle and other radar reflective structures configured for a high entrance angle.

In some examples, marking tape with radar reflective structures according to this disclosure will be resistant to corrosion in installed environments, and to retain dimensional stability. In examples that include a metal layer on the surface of the radar reflective structure, such as stamped foil, vapor deposited layer, or conductive ink, may be corrosion-protected by fully encapsulating with a protective layer comprising a weatherable, abrasion-resistant, low dielectric material to prevent the ingress of chlorides and water. Some examples may include an anti-corrosion surface treatment. Both metallic and non- metallic examples may be encapsulated with a weatherable, abrasion-resistant, low dielectric layer to prevent collection of debris that may interfere with the reflectivity. Some examples of pavement marking tapes with dimensionally stable arrays may be formed on filled rubber premix compositions that are not substantially deformed in operation.

Compact planar structure 900 may be assembled by providing a sensable layer 902, which may comprise retroreflective layer 906 and protective layer 904, and applying, such as by laminating, conformance layer 912 to the bottom surface of sensable layer 906. In some examples, a layer of adhesive or primer may be applied to the surface of one or more layers prior to laminating. The criteria for suitable adhesive materials and primers will be dependent in part upon the nature of the sheeting and the intended application. In some examples, either conformance layer 912 or a configuration member (not shown in FIG. 12) could be first applied to retroreflective layer 906. For instance, in one example, a retroreflective sheet may be applied to an aluminum conformance layer 912 followed by lamination of a configuration member, e.g., a mesh (not shown in FIG. 12). However, any metallic structures may not be between the radar reflecting structures and the incident radar radiation. Optional adhesive layer 914 may be applied to the compact planar structure 900 before application to a desired substrate, such as a roadway. A marking tape comprising compact planar structure 900 can withstand repeated traffic impact and shear stresses in combination with other effects of sunlight, rain, road oil, road sand, road salt, and vehicle emissions. In some examples, adhesive layer 914 comprises a pressure sensitive adhesive.

FIGS. 13A and 13B are conceptual diagrams illustrating example marking tape with a retroreflective sensable layer and a radar reflective layer according to one or more techniques of this disclosure. Compact planar structures 920 and 950 of FIGS. 13A and 13B are examples of compact planar structure 900 with a sensable layer comprising a retroreflective layer.

FIG. 13A includes sensable layer 921, radar reflective layer 940 and backing layer 934. Backing layer 934 comprises conformance layer 936, configuration member 932, and adhesive layer 938. As described above backing layer 934 may also include a scrim material (not shown in FIG. 13A). In some examples, radar reflective layer 940 may be included in backing layer 934, in examples in which the marking tape is configured to ensure metallic or other structures of the marking tape do not interfere with the radar reflective properties of the radar reflective layer.

Sensable layer 921 includes a protective layer 929 and retroreflective sheet 922. Protective sheet 929 is similar to protective layer 904 described above in relation to FIG. 12.

Enclosed-lens retroreflective sheet 922 may comprise a monolayer of retroreflective elements 924 formed into first portions of the monolayer arranged in an upwardly contoured profile 926A and second portions 928 of the monolayer are arranged a lower, sometimes substantially planar profile. First portions 926A are elevated above second portions 928 by configuration member 932. These upwardly contoured portions 926A, with their relatively vertical profiles may provide enhanced retroreflective performance. First, when the pathway article is oriented as a pavement marking or guard rail marking, the incidence angle or entrance angle of light to the upwardly contoured portions 926A may be lower than the incidence angle to the second lower portions 928. This may achieve and effective retroreflective result. Second, the higher elevation of upwardly contoured portions 926A may facilitate the run off of water that might degrade retroreflective performance. Third, in the example of pavement markings, upwardly contoured portions 926A have been observed to result in improved adhesion to the road surface.

Upwardly contoured portions 926A may be implemented in any way that will elevate portions of the retroreflective sheet. In the example of FIGS. 9B and 9C, such means is use of a configuration member. Configuration members may be of any shape so long as they elevate some portions of the retroreflective sheet. In some examples, the configuration member is a mesh or netting of strands or even simply an assembled array of unconnected strands. When the article is assembled the strands define the first upwardly contoured portions 926A and the openings between the strands define the second lower portions 928. Some examples of shapes may include rectangles, diamonds, hexagons, curves, circles, sinusoidal ridges (e.g., nested in parallel or intersecting), etc. Each second lower portion 928 may be essentially separated from neighboring lower portions or they may intersect, depending upon the shape of the first upwardly contoured portions 926A.

In the example of FIG. 13 A, configuration member 932 is directly attached to retroreflective sheet 922. In some examples, compact planar structure 920 may include a tie layer (not shown in FIG. 13A) between one or more layers. The tie layer may be a layer that adheres well to the surfaces of mating layers. For example, ethylene methacrylic acid will adhere to both aluminum and nitrile rubber layers. In other examples, conformance layer 936 may be directly attached to the bottom of the radar reflective layer 940, followed by a configuration member and adhesive layer 938. In some examples, the retroreflective sheet and configuration members may be substantially coextensive, while in other examples may be not co-extensive. In the example of FIG. 13A, backing layer 934 comprises configuration member 932 bonded to optional conformance layer 936.

FIG. 13B is another example of a compact planar structure including radar reflective structures, according to one or more techniques of this disclosure. Compact planar structure 950 is similar to compact planar structures 900 and 920 of FIGS. 12 and 13 A, with a different example of conformance members 952. Features among the figures with the same reference numbers have the same function and description.

FIG. 13B includes sensable layer 951, radar reflective layer 940 and backing layer 954. Backing layer 934 comprises optional conformance layer 936, and adhesive layer 938. As described above backing layer 934 may also include a scrim material (not shown in FIG. 13B). In some examples, radar reflective layer 940 may be included in backing layer 934 or may be considered a separate layer.

Sensable layer 951 includes a protective layer 929 and retroreflective sheet 922. Protective sheet 929 is similar to protective layer 904 described above in relation to FIG. 12. In the example of FIG. 13B configuration member 952 is applied to retroreflective sheet 922 followed by lamination of radar reflective layer 940, conformance layer 936 and adhesive layer 938. As with configuration member 932 of FIG. 13A, configuration members 952 may be polymeric. Some examples of polymeric materials may include polyurethanes and polyolefin copolymers such as polyethylene acid copolymer consisting of ethylene methacrylic acid 35 (EMAA), ethylene acrylic acid (EAA), ionically crosslinked EMAA or EAA.

Upward contoured portions 926B may be achieved by laminating configuration members 952 to any region beneath the retroreflective sheet 922. In other words, configuration members 952 may be placed between retroreflective sheet 922 and adhesive layer 938, which bonds the marking tape to a desired substrate, e.g., a roadway. Optional adhesive layer 938 may be applied before application to the desired substrate, Thus, the configuration member can be placed in any layer beneath the retroreflective sheet insofar as it results in the desired configuration. Because the purpose of the configuration member is to impart an upward profile to the retroreflective sheet, its placement can vary for processing

convenience.

In other examples, compact planar structures 900, 920 and 950 may be assembled by providing a sensable layer and backfilling upwardly contoured profiles with a filling material. The upwardly contoured profiles may be formed by variety of techniques. In one example, retroreflective sheet 922 may be gathered together in portions and any voids backfilled. In other examples, retroreflective sheet 922 may be fed into an embossing roll to form the upwardly contoured profiles of a variety of shapes, as described above. An embossing roll may have an advantage in causing less disruption of the sensable layer, when compared to laminating the sensable layer to a preformed configuration layer, such as in the example of Fig 13 A. Disruption may lead to reduction of retroreflective brightness or reduce physical integrity of the sheeting. Some examples of material that may be used as an embossed layer may include rubber or structured elastomer.

Forming the profiles may create voids or depressions in the back of the retroreflective sheet (i.e., the non-reflective side). It may be desirable to fill the voids with some material that provides sufficient dimensional stability to retain the described profiles. Backfill material may be conformable so the resultant marking tape is flexible and conformable while retaining the contoured profile described herein. For example, a polymeric film may be used as backfill material. The polymeric film may be heated to flow into the voids in the structured regions. Radar reflective layer 940 may be laminated or otherwise assembled to the sensable layer after the formation and backfill of the upwardly contoured profiles. As described above, a tie layer may be included between any of the layers.

Components of a marking tape that includes compact planar structures 900, 920 and 952 may be configured to be sufficiently conformable so that the desired upwardly contoured profiles 926A and 926B of retroreflective sheet 922 can be achieved. In some examples, configuration member, such as configuration members 932 and 952 may self-adhere to conformance layer 936, if present, which may have an advantage of improved durability when compared to other configurations. In addition to providing the functions disclosed herein, the configuration layer may impart improved mechanical properties to a pavement marking material in similar manner as the scrim layer described above in relation to FIG. 13 A. As described above, a variety of techniques may be used to add colorants to some portion the compact planar structures of this disclosures. Some examples may include a light and radar transmissive colored top film. In other examples, a colorless top film could be applied to a colored retroreflective sheet.

FIG. 14 is a flow chart illustrating an example technique for making a marking tape according to one or more techniques of this disclosure. The steps of FIG. 10 will be described in terms of FIGS. 12 - 13B, unless otherwise noted. The techniques in the description of FIG. 14 is just one example. In other examples, steps may be performed in a different order, and may include more steps or few steps then described in FIG. 14.

One technique for making a marking tape material according to one or more techniques of this disclosure may include providing a continuous base sheet including an upper surface and a lower surface (90). The base sheet may include any one or more of the layers included in backing layer 934, such as configuration member 932 and conformance layer 936. The base sheet may be one continuous length along the long axis, such as long axis 211 depicted in FIG. 4. In other examples, the base sheet may be a shorter length such as 15 cm, 1 meter or other lengths. The base sheet may be any width, as appropriate for the intended application, such as approximately 10 cm wide.

The techniques of this disclosure may include applying a sensable layer to the upper surface of the continuous base sheet, such as by laminating a surface of the sensable layer to the base sheet upper surface (92). The sensable layer may include features that are visible to the human eye or visual camera, such as retroreflective layer 922. The sensable may also include features such as magnetic elements that may be detectable by other sensors on a PAAV. In some examples, retroreflective layer 922 includes an embedded-lens retroreflective sheet, which may include a layer of transparent microspheres having front and back surfaces, a cover layer in which the front surfaces of the microspheres are embedded, and an associated reflective means behind the back surface of the microspheres. In other examples, retroreflective layer 922 may include a retroreflective sheet comprising a monolayer of cube-comer elements or non-metallic microspheres. In other examples, retroreflective layer 922 may include one or more first upwardly contoured profile 926A and 926B, which may be arranged in an interconnected network. As described above, examples of metallic retroreflective materials may be physically separated from the radar reflecting structures.

In some examples, a marking tape, including a compact planar structure, such as compact planar structure 950, may be further assembled by applying a continuous conformance layer, such as conformance layer 936 to the lower surface of the continuous base sheet (94). Conformance layer 936 may comprise a variety of materials, including aluminum, and may be applied along with a tie layer and a scrim layer. Some examples of marking tape may also include adhesive layer 938.

The marking tape may further be assembled by adding a radar reflective structure disposed between sensable layer 902 and the continuous base sheet, in the plane of the continuous base sheet (96). The radar reflective structure may be one of a plurality of radar reflective structures, such as radar reflective structures 220 - 224 depicted in FIG. 4. The radar reflective structures may be arranged at a variety of angles and spacings to perform various functions as described above in relation to FIGS. 1 - 3. Radar reflective structures may comprise a conductive material and have dimensions and spacing configured to reflect incident radar radiation from one or more radar transceivers in a PAAV.

The following are embodiments according to the present disclosure:

Embodiment 1. A radar reflecting structure device, the device comprising:

a first radar reflective element; and

a second radar reflective element, wherein:

the second radar reflective element is substantially parallel to the first radar reflective element; a radar signal that reflects off the first radar reflective element results in a first reflected signal; the radar signal that reflects off the second radar reflective element results in a second reflected signal;

the second reflected signal causes a phase interference in the first reflected signal;

the phase interference causes the first reflected signal and the second reflected signal to form a reflected beam, wherein the reflected beam comprises a direction of travel substantially opposite to a direction of travel of the radar signal.

Embodiment 2. The device of embodiment 1, wherein the first radar reflective element is the first radar reflective element of a plurality of radar reflective elements and the second radar reflective element is the second radar reflective element of the plurality of radar reflective elements, wherein:

a respective radar reflective element of the plurality of radar reflective elements is substantially parallel to the first radar reflective element,

each respective radar reflective element is arranged at distance from each adjacent radar reflective element such that the respective reflected signal from each respective radar reflective element causes a phase interference to form the reflected beam,

the reflected beam is at a maximum when the radar signal is substantially orthogonal to the

plurality of radar reflective elements.

Embodiment 3. The device of any combination of embodiments 1 - 2, wherein the first radar reflecting element and the second radar reflecting element are non-resonant radar reflecting elements.

Embodiment 4. The device of any combination of embodiments 1 - 3, wherein the first radar reflecting element and the second radar reflecting element each comprise a conductive strip in a dielectric substrate.

Embodiment 5. The device of any combination of embodiments 1 - 4, wherein the first radar reflecting element and the second radar reflecting element each comprise a slot in a conductive substrate, wherein each slot is defined by a first wall of length L, a second wall of length L, wherein the second wall is substantially parallel to the first wall, a third wall of length W, wherein the third wall is substantially orthogonal to the first wall and a fourth wall of length W, wherein the fourth wall is substantially parallel to the third wall, and

wherein the first radar reflecting element and the second radar reflecting element are arranged such that reflected beam is at a maximum when the radar signal is substantially orthogonal to the first wall and the second wall.

Embodiment 6. The device of any combination of embodiments 1 - 5, wherein the first wall and the second wall further comprise an arc of radius R, wherein the reflected beam is at a maximum when the radius R is in substantially the same direction as the direction of travel of the radar signal.

Embodiment 7. The device of any combination of embodiments 1 - 6, wherein the first radar reflecting element and the second radar reflecting element are resonant radar reflecting elements.

Embodiment 8. The device of any combination of embodiments 1 - 7, wherein the first radar reflecting element and the second radar reflecting element each comprise a conductive strip in a dielectric substrate, wherein each conductive strip comprises a long axis and a short axis, and wherein the long axis is a half wavelength of an expected frequency of the radar signal.

Embodiment 9. The device of any combination of embodiments 1 - 8, wherein the long axis of each conductive strip further comprises an arc of radius R, wherein the reflected beam is at a maximum when the radius R is in substantially the same direction as the direction of travel of the radar signal.

Embodiment 10. The device of any combination of embodiments 1 - 9, further comprising a plurality of conductive strips,

wherein the conductive strips are arranged in an array of conductive strips, and

wherein the array of conductive strips is arranged such that:

the long axis of each conductive strip is substantially parallel to the long axis of each other

conductive strip in the plurality of conductive strips;

the long axis of each conductive strip is arranged such that reflected beam is at a relative

maximum when the radar signal is substantially orthogonal to the long axis of each conductive strip.

Embodiment 11. The device of any combination of embodiments 1 - 10, wherein the first radar reflecting element and the second radar reflecting element each comprise a slot in a conductive substrate, wherein each slot is defined by a first wall of length L, a second wall of length L, wherein the second wall is substantially parallel to the first wall, a third wall of length W, wherein the third wall is substantially orthogonal to the first wall and a fourth wall of length W, wherein the fourth wall is substantially parallel to the third wall, wherein the length L is a half-wavelength of an expected frequency of the radar signal, and wherein the first radar reflecting element and the second radar reflecting element are arranged such that reflected beam is at a maximum when the radar signal is substantially orthogonal to the first wall and the second wall.

Embodiment 12. The device of any combination of embodiments 1 - 11, wherein the first wall and the second wall further comprise an arc of radius R, wherein the reflected beam is at a maximum when the radius R is in substantially the same direction as the direction of travel of the radar signal.

Embodiment 13. The device of any of any combination of embodiments 1 - 12, further comprising a plurality of slots,

wherein the slots are arranged in an array of slots, and

wherein the array of slots is arranged such that:

the length L of each slot is substantially parallel to the length L of each other slot in the plurality of slots;

the length L of each slot is arranged such that reflected beam is at a maximum when the radar signal is substantially orthogonal to the length L of each slot.

Embodiment 14. An article comprising:

a sheet material comprising:

a continuous base sheet including an upper surface and a lower surface;

a sensable layer applied to the upper surface of the continuous base sheet, wherein the sensable layer comprises a protective layer,

wherein the sheet material comprises a long axis and a short axis;

a radar reflecting structure:

wherein the radar reflective structure is disposed between the sensable layer and the continuous base sheet, in the plane of the continuous base sheet,

the radar reflective structure comprising:

a first radar reflective element; and

a second radar reflective element, wherein:

the second radar reflective element is substantially parallel to the first radar reflective element;

a radar signal that reflects off the first radar reflective element results in a first reflected signal;

the radar signal that reflects off the second radar reflective element results in a second reflected signal;

the second reflected signal causes a phase interference in the first reflected signal; the phase interference causes the first reflected signal and the second reflected signal to form a reflected beam, wherein the reflected beam comprises a direction of travel substantially opposite to a direction of travel of the radar signal.

Embodiment 15. The article of embodiment 14, wherein the sensable layer comprises at least one feature selected from a group comprising: a retroreflective feature, an infrared feature, a magnetically detectable feature.

Embodiment 16. The article of any combination of embodiments 14 - 15, further comprising one or more conformance members disposed between the sensable layer and the continuous base sheet, wherein the one or more conformance members are configured to form one or more upwardly contoured profile portions in the sensable layer.

Embodiment 17. The article of any combination of embodiments 14 - 16, further comprising a continuous conformance layer applied to the lower surface of the continuous base sheet.

Embodiment 18. The article of any combination of embodiments 14 - 17, wherein the radar reflecting structure comprises a conductive material.

Embodiment 19. The article of any combination of embodiments 14 - 18, wherein the radar reflecting structure comprises a high dielectric material.

Embodiment 20. The article of any combination of embodiments 14 -19, wherein the one or more conformance members comprise an embossed surface.

Embodiment 21. The article of any combination of embodiments 14 -20, wherein the radar reflective structure is a first radar reflective structure, the article further comprising a second radar reflective structure, wherein,

the first radar reflective structure is positioned one the continuous base sheet at a first angle relative to the long axis of the sheet material, and

the second radar reflective structure is positioned one the continuous base sheet at a second angle relative to the long axis of the sheet material.

Embodiment 22. The article of any combination of embodiments 14 - 21, wherein the first angle is different from the second angle.

Embodiment 23. The article of any combination of embodiments 14 -22, wherein the sheet material protects the radar reflective structure from deformation. Embodiment 24. The article of any combination of embodiments 14 - 23, further comprising a pressure sensitive adhesive layer applied to a lower surface of the continuous conformance layer.

Embodiment 25. The article of any combination of embodiments 14 - 24, wherein the first angle of the first radar reflective structure and the second angle of the second radar reflective structure are configured to form a code, wherein the code is configured to convey information based on a reflection of a radar signal from the first radar reflective structure and the second radar reflective structure.

Embodiment 26. The article of any combination of embodiments 14 - 24, further comprising a spacing length between the first radar reflective structure and the second radar reflective structure, wherein the spacing length is configured to form a code, wherein the code is configured to convey information based on a reflection of a radar signal from the first radar reflective structure and the second radar reflective structure.

Embodiment 27. The article of any combination of embodiments 14 - 26, wherein the information conveyed comprises one or more characteristics of a vehicle pathway.

Embodiment 28. The article of any combination of embodiments 14 - 27, wherein the one or more characteristics comprise a potential hazard on the vehicle pathway, and wherein the one or more characteristics comprise one or more of: a nature of the potential hazard, a location of the potential hazard relative to the vehicle pathway, and a portion of the vehicle pathway affected by the potential hazard.

Embodiment 29. The article of any combination of embodiments 14 - 28, wherein the one or more characteristics is selected from a group comprising: a slope of the pathway, a curvature of the pathway, a change in recommended speed of a vehicle on the vehicle pathway, etc.

Embodiment 30. A system for vehicles on a traffic-bearing surface, the system comprising:

a pathway configured to support vehicle traffic;

a pathway-article assisted vehicle (PAAV) comprising:

one or more radar transceiver devices;

one or more sensor devices;

one or more processor circuits configured to interpret a first signal from the one or more radar transceiver devices and a second signal from the one or more sensor devices;

a pathway article comprising a radar reflecting structure,

wherein the pathway article is arranged on the pathway within a field of regard (FOR) of the one or more radar transceiver devices, and

wherein the radar reflective structure comprises: a first radar reflective element; and

a second radar reflective element, wherein:

Embodiment 31. The system of embodiment 30, wherein the PAAV comprises one or more sensor devices selected from a group comprising: an image processing device, a magnetic sensing device, a LIDAR device, and a global positioning system (GPS) device.

Embodiment 32. The system of any combination of embodiments 30 - 31, wherein the image processing device comprises one or more devices selected from a group comprising: an optical camera, an infrared (IR) camera, an ultraviolet camera (UV).

Embodiment 33. The system of any combination of embodiments 30 - 32, wherein the pathway article is a marking tape.

Embodiment 34. The system of any combination of embodiments 30 - 33, wherein the marking tape is applied to a protective barrier along the edge of the pathway.

Embodiment 35. The system of any combination of embodiments 30 - 34, wherein the marking tape is applied to a temporary warning device positioned on the pathway within the FOR of the one or more radar transceiver devices.

Embodiment 36. The system of any combination of embodiments 30 - 35, wherein the temporary warning device is a vehicle impact reducing barrel.

Embodiment 37. The system of any combination of embodiments 30 - 36, wherein the pathway comprises pavement to support vehicle traffic and pathway article is a pavement marking tape.

Embodiment 38. The system of any combination of embodiments 30 - 37, wherein the pathway is a two-way pathway,

wherein the pathway article is disposed along a centerline of the two-way pathway, and

wherein the one or more processing circuits is configured to determine a location of the centerline of the two-way pathway based on a radar signal reflected from the radar reflective structure.

Embodiment 39. The system of any combination of embodiments 30 - 38, wherein the pathway article is disposed along an edge of a pathway and wherein the one or more processing circuits is configured to determine a location of the edge of the two-way pathway based on a radar signal reflected from the radar reflective structure.

Embodiment 40. The system of any combination of embodiments 30 - 39, wherein the pathway article marks a hazard along the pathway

Embodiment 41. The system of any combination of embodiments 30 - 40, wherein the pathway article is disposed at a lane location of a pathway and wherein the one or more processing circuits is configured to determine the lane location based on a radar signal reflected from the radar reflective structure.

Embodiment 42. The system of any combination of embodiments 30 - 41, wherein the radar reflective structure comprises:

a material with a coefficient of thermal expansion (CTE), wherein the first radar reflective element and the second radar reflective element are arranged with a first spacing at a first temperature and are arranged at a second spacing at a second temperature, based on the CTE,

wherein the first radar reflective element and the second radar reflective element are configured to reflect a radar signal with a first return signal at the first spacing and to reflect the radar signal with a second return signal at the second spacing,

wherein the one or more processors is configured to determine a temperature of the radar

reflective structure based on whether the one or more radar transceiver devices receives the first return signal or receives the second return signal.

Embodiment 43. The system of any combination of embodiments 30 - 42, wherein the radar reflective structure is a first radar reflective structure of a plurality of radar reflective structures arranges within the FOR of the radar transceiver device.

Embodiment 44. The system of any combination of embodiments 30 - 43,

wherein the plurality of radar reflective structures is arranged on the pathway article to form a code, wherein the code is configured to convey information based on a reflection of a radar signal from the plurality of radar reflective structures, and

wherein the one or more processor circuits is configured to interpret the information based on the code. Embodiment 45. The system of any combination of embodiments 30 - 44,

wherein the information based on the code comprises one or more characteristics of the pathway;

wherein the one or more processors is configured to:

determine the one or more characteristics of the vehicle pathway, based in part on interpretation of the information;

determine an adjustment for one or more functions of the PAAV based at least in part on the one or more characteristics; and

control the determined adjustment.

Embodiment 46. The system of any combination of embodiments 30 - 45, wherein the one or more processing circuits controls the determined adjustment for one or more functions of the PAAV based on the information in conjunction with a human operator.

Embodiment 47. The system of any combination of embodiments 30 - 46, wherein the one or more processors are further

configured to output a notification to an occupant of the PAAV based on the information.

Embodiment 48. The system of any combination of embodiments 30 - 47,

wherein the one or more processors are further configured to determine environmental conditions in a vicinity of the PAAV based on the second signal from the one or more sensor devices, wherein the environmental conditions in the vicinity of the PAAV comprise one or more of: air

temperature, precipitation level, precipitation type, incline of the vehicle pathway, presence of other vehicles and estimated friction level between the PAAV tires and the vehicle pathway, and wherein the determined adjustment for one or more functions of the PAAV is based at least in part on the environmental conditions in a vicinity of the PAAV.

Embodiment 49. The system of any combination of embodiments 30 - 48, wherein the one or more processors are configured to control the determined adjustment by one or more of: a change a speed of the PAAV, change a status of a headlight, change a damping coefficient of a suspension system of the PAAV, apply a force to the steering system of the PAAV and change the interpretation of one or more inputs from sensors.

Embodiment 50. A method for making a marking tape material comprising:

providing a continuous base sheet including an upper surface and a lower surface;

applying a sensable layer to the upper surface of the continuous base sheet;

applying a continuous conformance layer to the lower surface of the continuous base sheet; adding a radar reflecting structure device disposed between the sensable layer and the continuous base sheet, in a plane of the continuous base sheet, wherein the radar reflective structure comprises a first radar reflective element and a second radar reflective element.

Embodiment 51. The method of embodiment 50, wherein the sensable layer is a retroreflective layer, the method further comprising:

(a) providing an enclosed-lens retroreflective sheet having a top surface and a bottom surface and

comprising a cover layer and a monolayer of retroreflective elements;

(b) applying a conformance layer to the bottom surface of the retroreflective sheet; and

(c) laminating a configuration member to the conformance layer thereby creating first portions and second portions in the retroreflective sheet, wherein the first portions are arranged in an upwardly contoured profile and the second portions being arranged in a lower, substantially planar position.

Embodiment 52. The method of any combination of embodiments 50 - 51, wherein the configuration member is a polyolefin copolymer selected from a group consisting of ethylene methacrylic acid

(EMAA), ethylene acrylic acid (EAA), ionically crosslinked EMAA, and ionically crosslinked EAA.

Embodiment 53. The method of any combination of embodiments 50 - 52 further comprising applying a layer of adhesive to a bottom surface of the configuration member or to the conformance layer.

Embodiment 54. The method of any combination of embodiments 50 - 53, wherein the configuration member is a mesh.

Embodiment 55. The method of any combination of embodiments 50 - 54, wherein the retroreflective sheet is selected from a group consisting of embedded-lens retroreflective sheet and encapsulated-lens retroreflective sheet.

Embodiment 56. The method of any combination of embodiments 50 - 55, wherein the embedded-lens retroreflective sheet comprises a layer of transparent microspheres having front and back surfaces, a cover layer in which the front surfaces of the microspheres are embedded, and an associated reflective means behind the back surface of the microspheres.

Embodiment 57. The method of any combination of embodiments 50 - 56, wherein the retroreflective sheet comprises a monolayer of cube-comer elements.

Embodiment 58. The method of any combination of embodiments 50 - 57, wherein the first portions are arranged in an interconnected network. Embodiment 59. The method of any combination of embodiments 50 - 58 further comprising applying a protective coating on a cover layer of the sensable layer.

Embodiment 60. The method of any combination of embodiments 50 - 59 further comprising applying antiskid particles on the protective coating.

Embodiment 61. The method of any combination of embodiments 50 - 60, wherein the sensable layer comprises a conformable magnetic layer comprising a binder and a sufficient amount of magnetic particles within the binder to provide a magnetic signal.

Embodiment 62. The method of any combination of embodiments 50 - 61, wherein the magnetic layer comprises sections of alternating polarity along the length of the continuous base sheet.

Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.

Claims

CLAIMS:

1. An article comprising:

a sheet material comprising:

a continuous base sheet including an upper surface and a lower surface;

wherein the sheet material comprises a long axis and a short axis;

a radar reflecting structure:

the radar reflective structure comprising:

a first radar reflective element; and

a second radar reflective element, wherein:

2. The article of claim 1, wherein the sensable layer comprises at least one feature selected from a group comprising: a retroreflective feature, an infrared feature, a magnetically detectable feature.

3. The article of any of the preceding claims, further comprising one or more conformance members disposed between the sensable layer and the continuous base sheet, wherein the one or more conformance members are configured to form one or more upwardly contoured profile portions in the sensable layer.

4. The article of any of the preceding claims, further comprising a continuous conformance layer applied to the lower surface of the continuous base sheet.

5. The article of any of the preceding claims, wherein the radar reflecting structure comprises a conductive material.

6. The article of any of the preceding claims, wherein the radar reflecting structure comprises a high dielectric material.

7. The article of any of the preceding claims, wherein the one or more conformance members comprise an embossed surface.

8. The article of any of the preceding claims, wherein the radar reflective structure is a first radar reflective structure, the article further comprising a second radar reflective structure, wherein, the first radar reflective structure is positioned one the continuous base sheet at a first angle relative to the long axis of the sheet material, and

9. The article of any of the preceding claims, wherein the first angle is different from the second angle.

10. The article of any of the preceding claims, wherein the first angle of the first radar reflective structure and the second angle of the second radar reflective structure are configured to form a code, wherein the code is configured to convey information based on a reflection of a radar signal from the first radar reflective structure and the second radar reflective structure.

11. The article of any of the preceding claims, further comprising a spacing length between the first radar reflective structure and the second radar reflective structure, wherein the spacing length is configured to form a code, wherein the code is configured to convey information based on a reflection of a radar signal from the first radar reflective structure and the second radar reflective structure.

12. The article of any of the preceding claims, wherein the one or more characteristics comprise a potential hazard on the vehicle pathway, and wherein the one or more characteristics comprise one or more of: a nature of the potential hazard, a location of the potential hazard relative to the vehicle pathway, and a portion of the vehicle pathway affected by the potential hazard.

13. The article of any of the preceding claims, wherein the one or more characteristics is selected from a group comprising: a slope of the pathway, a curvature of the pathway, a change in recommended speed of a vehicle on the vehicle pathway, etc.

14. A system for vehicles on a traffic-bearing surface, the system comprising:

a pathway configured to support vehicle traffic;

a pathway-article assisted vehicle (PAAV) comprising: one or more radar transceiver devices;

one or more sensor devices;

a pathway article comprising a radar reflecting structure,

wherein the radar reflective structure comprises:

a first radar reflective element; and

a second radar reflective element, wherein:

15. The system of claim 14, wherein the PAAV comprises one or more sensor devices selected from a group comprising: an image processing device, a magnetic sensing device, a LIDAR device, and a global positioning system (GPS) device,

wherein the image processing device comprises one or more devices selected from a group comprising: an optical camera, an infrared (IR) camera, an ultraviolet camera (UV); and

wherein the pathway article is a marking tape.