WO2012013228A1

WO2012013228A1 - A method and a system for monitoring traffic of vehicles

Info

Publication number: WO2012013228A1
Application number: PCT/EP2010/060974
Authority: WO
Inventors: Robert Nordentoft; Gabriel Felipe GARRIDO GONZÁLEZ; David PÉREZ CASARES
Original assignee: Traffic Network Solutions, S. L.
Priority date: 2010-07-28
Filing date: 2010-07-28
Publication date: 2012-02-02
Also published as: ES2424397B1; ES2424397R1; ES2424397A2

Abstract

The method comprises: - detecting a plurality of mobile devices (Mv, Mp) at different geographical positions by means of receiving, by several sensor devices (D1, D2) disposed at several known locations along a roadway (R), identifying information related to said mobile devices (Mv, Mp) contained in wireless signals; - determining which of said mobile devices (Mv, Mp) detected at least at two sensor devices (D1, D2) are associated to vehicles (V1, V2, V3), by processing the received identifying information to find out the type of mobile device it relates to; -establishing an exclusion velocity limit dynamically according to the velocities of the mobile devices (Mv) associated to vehicles (V1, V2, V3); and - identifying slow-moving mobile devices (Mp) with a velocity below said exclusion velocity limit, and monitoring traffic of the mobile devices (Mv) which are not said slow-moving mobile devices (Mp). The system is adapted to implement the method.

Description

A method and a system for monitoring traffic of vehicles

Field of the art

The present invention generally relates, in a first aspect, to a method for monitoring traffic of vehicles which comprises using wireless short range technology signals for detecting mobile devices, and more particularly to a method providing a dynamic discrimination between those mobile devices being associated to vehicles from those which are not.

A second aspect of the invention concerns to a system for monitoring traffic of vehicles, and more particularly to a system having means intended for carrying out the dynamic discrimination of the method of the first aspect.

Prior State of the Art

There are several proposals related to methods and systems for monitoring traffic of vehicles, which disclose to detect vehicles from information acquired from some kind of wireless short range technology signals interchanged between sensor devices placed along a roadway and mobile devices circulating by said roadway, some of which are associated to vehicles.

One of the main problems that said proposals have to cope with is that related to the discrimination, from all the mobile objects detected, between those which are really, or very likeable, associated to vehicles from those which are not, such as those carried by pedestrians or cyclists.

International application WO2009/086565A1 discloses one of said proposals, particularly related to monitoring traffic using identification information obtained using a Bluetooth protocol, acquired by scanning a route for discoverable Bluetooth devices, by means of several sensors placed at known locations along a route. Information related to the sensor devices, such as sensor identifiers, location, etc, is associated to identifiers of the Bluetooth devices contained in the acquired information, which includes at least their Media Access Control (MAC) address. No mention is done about discarding any of the devices detected, and only a general statement indicating that pedestrians are more easily detected than vehicles because of the time a typical Bluetooth inquiry scan takes is done, to justify that, in order to detect vehicles, the scan must be configured to be carried out faster.

However, it is known by the present inventors that the product marketed by the applicant of WO2009/086565A1 carries out such a discrimination between vehicles and pedestrians, cyclists or other slow objects, just by using a simple exclusion velocity threshold, which determines that objects moving at a speed lower than said exclusion threshold are considered as not being associated to vehicles, and thus are discarded from traffic monitoring.

US65051 14B2 describes a system and a method for traffic monitoring and prediction of traffic intensity. The method comprises the steps of: determining at least twice, within a specified time interval, geographical positions of a plurality of mobile devices in a mobile telecommunications network by means of measuring a property of signals transmitted between said mobile devices and base stations in said mobile telecommunications network; comparing at least a subset of said geographical positions with a route of a road provided in a route database in order to identify mobile devices having routes corresponding to at least a part of said road route; calculating a velocity for said identified mobile devices based on said at least two positions; and comparing said calculated velocity of at least one identified mobile device with a reference velocity of said road in order to predict traffic intensity on said road.

Using wireless short range signals as said signals transmitted between the mobile devices and the base station is disclosed in US65051 14B2, and more specifically it is disclosed to use Bluetooth transceivers.

US65051 14B2 copes with the problem stated above, related to the discrimination between the objects associated to vehicles from those which are not. In fact, its granted claim 1 includes limitations offering a basic solution to that problem, which were not initially included in claim 1 of the original application. That solution is provided by the steps of identifying slow-moving mobile devices having a velocity being below an exclusion velocity limit, and discarding said so identified slow-moving vehicles from the step of comparing its velocity with the reference velocity of the road.

In US65051 14B2 specification there is also described to refine the process of discrimination between relevant signals coming from units located on a thoroughfare versus uninteresting signals coming from neighbouring areas or from people walking in neighbouring areas, by making test vehicles equipped with mobile devices travel the relevant areas, and provide data relevant to the computation of speed and location to be used as a local benchmark.

US2009153364 discloses a system and a method for calculating the travel time of vehicles between at least two points, acquiring the MAC of a WLAN device carried by the vehicles, included in a wireless signal transmitted there from, and assigning to it a timestamp and an location identifier, at each point that is detected by a respective detection device, sending the information to a central server, where travel time is calculated. In the specification of US2009153364 it is stated that the WLAN device can be an 802.1 1 a, 802.1 1 g, or 802.1 1 η device or it can be another type of device capable of transmitting a wireless or radio signal.

US2009153364 specification discloses to discard those devices carried by pedestrians, and even vehicles that are stopped, for example, to refuel, whose computed and recorded travel times are out of a standard deviation of the average travel time of the vehicles.

None of the cited proposals disclose to carry out the mentioned discarding or discrimination between vehicles and other kind of detected mobile objects, by first reliably determining some mobile objects to be associated to vehicles, which are not test vehicles but vehicles circulating within the flow of traffic to be monitored, and by providing an exclusion velocity threshold dynamically adjustable as a function of said mobile objects associated to vehicles.

Description of the Invention

It is necessary to offer an alternative to the state of the art which covers the gaps found therein and which provides such a proposal.

To that end, the present invention provides, in a first aspect, a method for monitoring traffic of vehicles, comprising the steps of:

a) detecting a plurality of mobile devices at two respective geographical positions, at two different moments, by means of receiving by a first and a second sensor devices disposed, respectively, at a first and a second known locations along a roadway, identifying information related to said mobile devices contained in wireless signals transmitted there from according to a wireless short range technology, and

b) identifying, from said plurality of detected mobile devices, slow-moving mobile devices having a velocity being below an exclusion velocity limit, and monitoring traffic of the mobile devices which are not said slow-moving mobile devices.

In a characteristic manner, the method of the first aspect of the invention comprises, prior to said slow-moving mobile devices identifying step:

i) determining which of said plurality of mobile devices detected twice are associated to vehicles, by processing, for each of said plurality of mobile devices, at least part of said received identifying information to find out the type of mobile device it relates to; and

ii) establishing said exclusion velocity limit dynamically according to the velocities of the mobile devices determined to be associated to vehicles.

In other words, step i) is a selection step which provides the reliable determination of those mobile devices associated to vehicles (cars, buses, etc.), said determined mobile devices being considered as patterns whose velocities are used to define said exclusion velocity.

Depending on the embodiment the exclusion velocity will be substantially equal to the one of the slowest (at a specific moment) mobile device determined to be associated to a vehicle, or to the velocities of part or all of the mobile devices determined to be associated to vehicles operated in any manner a person skilled in the art knows, such as for example by averaging their values, etc.

Depending on the embodiment of the method of the first aspect of the invention, said identifying information of each mobile device comprises only a media access control address or further a class data field.

For some embodiments said received identifying information processed to find out of the type of mobile device it relates to is contained in at least part of said media access control address and/or in said class data field.

For an embodiment of the method of the first aspect of the invention, it comprises encrypting at least part of said identifying information at each of said first and second sensor devices.

Although the method of the first aspect of the invention is not limited to any wireless short range technology, and it could be used for example for a WiFi technology, for a preferred embodiment the wireless short range technology is a Bluetooth® technology.

For an embodiment related to the use of said Bluetooth® technology, said received identifying information processed to find out of the type of mobile device it relates to is contained in only part of said media access control address, which for a more particular embodiment is the MAC header.

Said type of mobile device is, for an embodiment, a type of Bluetooth® device for vehicles, such as a TomTom® or a Parrot® device, which can be known from the vendor indicated in the MAC header.

For other types of devices it is enough, or even necessary because the vendor information is not defining the type of device, to consult the class data field. That is the case, for example, of those devices whose class data field indicates that the device is a hands free device, which permits to reliably determine that said device is certainly associated to a vehicle.

With the purpose of avoiding registering and processing redundant data related to a specific mobile device, and thus reducing the amount of data to be further processed, the method of the invention comprises, for an embodiment, generally prior to said steps i) and ii), at each of said first and second sensor devices, detecting several times the same mobile device by receiving corresponding wireless signals, selecting from said several detections the one associated to the wireless signal received at the sensor device with a higher power (and optionally the more delayed wireless signal), and discard the rest of said several detections.

It is assumed that the selected highest power signal corresponds to the mobile device which is closest to the sensor device receiving its wireless signal.

Many vehicles can contain several mobile devices with wireless short range technology detectable according to the method of the first aspect of the invention. In order to take that case into account, and having in mind that what is wanted to be monitored is the traffic of vehicles, nor of each individual mobile device, for an embodiment of the method it comprises determining, from the mobile devices determined to be associated to vehicles, that there are many mobile devices associated to the same vehicles, and creating there from clusters of mobile devices, each cluster associated to one and the same vehicle, and monitoring the traffic of vehicles by monitoring said clusters.

Said determining that many mobile devices are associated to one and the same vehicle is established if said mobile devices are detected at substantially the same moment or within a predetermined time interval, at least at each of said first and second sensor devices or of other analogous sensor devices.

The higher the number of sensor devices that have detected several mobile devices at substantially the same moment or within a predetermined time interval, the more likely said several mobile devices are associated to the same vehicle.

Although the method of the first aspect of the invention has been explained referring to a first sensor device and a second sensor device, that has been done only for making a clearer description. Obviously the method of the invention is applicable to a plurality of sensor devices, and everything explained with relation to the first and second sensor devices can be extrapolate to any pair of two consecutive sensor devices of said plurality of sensor devices.

Depending on the embodiment, the requirements to consider two or more mobile devices as belonging to the same cluster, i.e. to be associated to the same vehicle, can be more or less restrictive, being the most restrictive requirement that referring to the detection at substantially the same moment, and lesser restrictive requirements those with longer predetermined time intervals within to detect said mobile devices.

For an embodiment those requirements vary along time, particularly they become less restrictive as the number of sensor devices that detect several mobile devices at said substantially the same moment or within said predetermined time interval increases.

For said embodiments referring to the creation of clusters of mobile devices associated to the same vehicles, the monitoring of traffic will be carried out on said clusters. Those mobile devices which have not been included in a cluster of two or more elements, i.e. mobile devices, can be monitored as mobile devices or as clusters of one element each.

For an embodiment the method comprises, to statistically calculate traffic variables, as average speed, traffic distribution, etc., to weight data according to the number of clusters.

As for said monitoring of traffic of vehicles is concerned, depending on the embodiment, it relates to one or more parameters referred to the level of service and/or vehicles distribution of said roadway.

Examples of parameters defining said level of service are next: trip time between at least said and/or other first and second sensor devices, average vehicles velocity and traffic density at each sensor device.

For an embodiment said vehicles distribution is calculated by the percentage of vehicles captured in said second sensor device that come from said first sensor device, or in any second sensor device coming from a first sensor device of any pair of consecutive sensor devices.

The method of the invention also comprises, for an embodiment, to carry out the described identifying of slow-moving mobile devices only if the average velocity of the mobile devices determined to be associated to vehicles is above a traffic jam velocity, because if the vehicles are in a traffic jam situation, their velocities are so low that can not be taken as an exclusion velocity limit for discriminating them from pedestrians.

A second aspect of the invention concerns to a system for monitoring traffic of vehicles, comprising:

- a plurality of sensor devices disposed, respectively, at a plurality of known locations along a roadway, each sensor device having a local electronic system and wireless short range technology communications capabilities, and being arranged and intended for detecting a plurality of mobile devices circulating by said roadway, by means of receiving identifying information related to said mobile devices contained in wireless signals transmitted there from according to said wireless short range technology, and - means for identifying, from said plurality of detected mobile devices, slow- moving mobile devices having a velocity being below an exclusion velocity limit, and monitoring traffic of the mobile devices which are not said slow-moving mobile devices.

In the system of the second aspect of the invention, said means are also intended for carrying out the steps i) and ii) of the method of the first aspect of the invention.

For an embodiment said means are included in one or more of said local electronic systems of said plurality of sensor devices, which implements one or more algorithms (software and/or hardware based) to carry out said steps i) and ii) and said mobile devices detections.

For an alternative embodiment said means comprise a central server communicated with said plurality of sensor devices to receive at least said identifying information related to said mobile devices, said central server also implementing one or more algorithms (software or hardware based) to carry out at least said steps i) and ii).

In a subsequent section, a preferred embodiment will be described with more detail, where the system of the second aspect of the invention includes said central server.

Brief Description of the Drawings

The previous and other advantages and features will be more fully understood from the following detailed description of embodiments with reference to the attached drawings, which must be considered in an illustrative and non-limiting manner, in which :

Fig. 1 is a schematic view of the system of the second aspect of the invention applied to a road where vehicles and pedestrians are circulating through and adjacent thereto.

Detailed Description of Several Embodiments

A simple embodiment of the system provided by the second aspect of the invention is illustrated in Fig. 1 where two sensor devices D1 , D2 are disposed at two respective known locations adjacent roadway R.

There are three vehicles V1 , V2, V3 carrying mobile devices Mv and circulating through the illustrated roadway R, and one pedestrian P1 carrying a respective mobile device Mp is also walking through said roadway R and another one P2 carrying another mobile device Mp is walking through a zone adjacent thereto, such as a pavement.

Each sensor device D1 , D2 has a local electronic system and wireless short range technology communications capabilities with a coverage range which embraces at least the width of the roadway R, such that it detects the mobile devices Mv contained in the vehicles V1 , V2, V3 entering said coverage range, receiving, after a request, the above described identifying signals from any mobile device Mv, Mp within the coverage range.

The sensor devices D1 , D2 are connected to a central server Sc, to which they transmit the identifying information received from the mobile devices Mv, Mp.

This central server Sc is in charge of carrying out the steps i) and ii) of the method of the first aspect f the invention, described in a previous section, and also the identifying of the slow-moving mobile devices Mp having a velocity being below an exclusion velocity limit, i.e. the ones carried by pedestrians P, by implementing one or more algorithms (software and/or hardware based), in order to monitor only the mobile devices Mv associated to vehicles V1 , V2, V3.

Said central server Sc is also intended, for some embodiments, for carrying out the actions of the method related to the higher power wireless signal selection, the creation of clusters and the statistical calculus of traffic variables data weighted according to the number of clusters, as explained in a previous section.

It can be seen in Fig. 1 how one of the vehicles V1 , V2, V3, specifically vehicle

V2, contains two mobile devices Mv. As explained in a previous section, according to the method of the first aspect of the invention, said two devices Mv are grouped into a cluster related to said vehicle V2, in order to monitor vehicle V2 by monitoring clusters instead of monitoring each mobile device Mv as being associated to a different vehicle.

In other words, in Fig. 1 there are illustrated three vehicles V1 , V2, V3, each being associated to a respective cluster, two of them including only a mobile device Mv

(vehicles V1 and V3), and another one (vehicle V2) including two mobile devices Mv.

Each sensor device D1 , D2 is intended for time stamping the received identifying information and to detect the power of the wireless signals received.

In connection with its respective electronic system, each sensor devices D1 , D2 has a respective GPS unit to synchronize with the rest of the sensors devices D1 , D2 and to detect their geographical locations periodically.

For an embodiment said sensor devices D1 , D2 are intended for sending to the central server Sc the received identifying information, once time stamped, the values of said detected wireless signals power and the geographical location associated to each mobile device detection Mv, Mp.

Each of the sensor devices D1 , D2 is, for some embodiments, intended for encrypting at least part of the received identifying information related to said mobile devices Mv, Mp, and to send it to said central server Sc once encrypted, and optionally also to store it, in an encrypted form, in respective local memories of its respective local electronic systems.

A person skilled in the art could introduce changes and modifications in the embodiments described without departing from the scope of the invention as it is defined in the attached claims.

Claims

1 . - A method for monitoring traffic of vehicles, comprising the steps of:

a) detecting a plurality of mobile devices (Mv, Mp) at two respective geographical positions, at two different moments, by means of receiving by a first (D1 ) and a second (D2) sensor devices disposed, respectively, at a first and a second known locations along a roadway (R), identifying information related to said mobile devices (Mv, Mp) contained in wireless signals transmitted there from according to a wireless short range technology, and

b) identifying, from said plurality of detected mobile devices (Mv, Mp), slow- moving mobile devices (Mp) having a velocity being below an exclusion velocity limit, and monitoring traffic of the mobile devices (Mv) which are not said slow-moving mobile devices (Mp);

said method being characterised in that it comprises, prior to said slow-moving mobile devices (Mp) identifying step:

i) determining which of said plurality of mobile devices (Mv, Mp) detected twice are associated to vehicles (V1 , V2, V3), by processing, for each of said plurality of mobile devices (Mv, Mp), at least part of said received identifying information to find out the type of mobile device it relates to; and

ii) establishing said exclusion velocity limit dynamically according to the velocities of the mobile devices (Mv) determined to be associated to vehicles (V1 , V2, V3).

2. - A method as per claim 1 , wherein it comprises, at each of said at least first (D1 ) and second (D2) sensor devices, detecting several times the same mobile device (Mv, Mp) by receiving corresponding wireless signals, selecting from said several detections the one associated to the wireless signal received at the sensor device (D1 , D2) with a higher power, and discard the rest of said several detections.

3. - A method as per claim 1 or 2, wherein it comprises determining, from the mobile devices (Mv) determined to be associated to vehicles (V1 , V2, V3), that there are many mobile devices (Mv) associated to the same vehicles, and creating therefrom clusters of mobile devices, each cluster associated to one and the same vehicle, and monitoring the traffic of vehicles (V1 , V2, V3) by monitoring said clusters.

4. - A method as per claim 3, wherein said determining that many mobile devices (Mv) are associated to one and the same vehicle is established if said mobile devices (Mv) are detected at substantially the same moment or within a predetermined time interval, at least at each of said first (D1 ) and second (D2) sensor devices or of other analogous sensor devices.

5. - A method as per claim 4, wherein to statistically calculate traffic variables data is weighted according to the number of clusters.

6. - A method as per claim 1 or 2, wherein said identifying information of each mobile device (Mv, Mp) comprises a media access control address.

7.- A method as per claim 6, wherein said identifying information of each mobile device (Mv, Mp) further comprises a class data field.

8.- A method as per claim 6 or 7, wherein said received identifying information processed to find out of the type of mobile device (Mv, Mp) it relates to is contained in at least part of said media access control address and/or in said class data field.

9.- A method according to any of the previous claims, wherein said wireless short range technology is a Bluetooth® technology.

1 0.- A method as per claim 9 when depending on claim 8, wherein said received identifying information processed to find out of the type of mobile device (Mv, Mp) it relates to is contained in only part of said media access control address.

1 1 .- A method as per claim 1 0, wherein said part of said media access control address processed to find out of the type of mobile device it relates to is the media access control address header.

1 2.- A method as per claim 9, 10 or 1 1 , wherein said type of mobile device is a type of Bluetooth® device for vehicles.

1 3.- A method as per any of the previous claims, wherein it comprises encrypting at least part of said identifying information at each of said first (D1 ) and second (D2) sensor devices.

14. - A method as per any of the previous claims, wherein said monitoring of traffic of vehicles relates to at least one parameter referred to at least one of the level of service and vehicles distribution of said roadway (R).

15. - A method as per claim 14, wherein said level of service is defined by at least the next parameters: trip time between at least said and/or other first (D1 ) and second (D2) sensor devices, average vehicles velocity and traffic density at each sensor device.

16. - A method as per claim 14, wherein said vehicles distribution is calculated by the percentage of vehicles captured in said second sensor device (D2) that come from said first sensor device (D1 ).

1 7. - A method according to claim 1 , wherein said identifying of slow-moving mobile devices (Mp) is carried out only if the average velocity of the mobile devices (Mv) determined to be associated to vehicles (V1 , V2, V3) is above a traffic jam velocity.

1 8.- A system for monitoring traffic of vehicles, comprising: - a plurality of sensor devices (D1 , D2) disposed, respectively, at a plurality of known locations along a roadway (R), each sensor device (D1 , D2) having a local electronic system and wireless short range technology communications capabilities, and being arranged and intended for detecting a plurality of mobile devices (Mv, Mp) circulating by said roadway, by means of receiving identifying information related to said mobile devices (Mv, Mp) contained in wireless signals transmitted there from according to said wireless short range technology, and

- means for identifying, from said plurality of detected mobile devices (Mv, Mp), slow-moving mobile devices (Mp) having a velocity being below an exclusion velocity limit, and monitoring traffic of the mobile devices (Mv) which are not said slow-moving mobile devices (Mp);

said system being characterised in that said means are also intended for carrying out the steps i) and ii) of the method as per any of claims 1 to 17.

19. - A system as per claim 18, wherein each of said plurality of sensor devices (D1 , D2) is intended for time stamping the received identifying information.

20. - A system as per claim 18 or 19, wherein each of said plurality of sensor devices (D1 , D2) is able to detect the power of the wireless signals received.

21 . - A system as per claim 18, 19 or 20, wherein each of said plurality of sensor devices (D1 , D2) has a respective GPS unit to synchronize said plurality of sensors devices (D1 , D2) and to detect their geographical locations periodically.

22. - A system as per any of claims 18 to 21 , wherein said means are included in at least one of said local electronic systems of said plurality of sensor devices (D1 , D2).

23. - A system as per any of claims 18 to 21 , wherein said means comprise a central server (Sc) communicated with said plurality of sensor devices (D1 , D2) to receive at least said identifying information related to said mobile devices (V1 , V2, V3, P1 , P2).

24. - A device as per claim 23 when depending on any of claims 20 to 21 , wherein said plurality of sensor devices (D1 , D2) are intended for sending to said central server (Sc) said received identifying information once time stamped, the values of said detected wireless signals power and the geographical location associated to each mobile device detection (Mv, Mp).

25. - A system as per claim 23 or 24, wherein said plurality of sensor devices (D1 , D2) are intended for encrypting at least part of said received identifying information related to said mobile devices (Mv, Mp), and at least send it to said central server (Sc) once encrypted.

26. - A system as per claim 25, wherein said plurality of sensor devices (D1 , D2) are intended for also storing in respective local memories of said local electronic systems said encrypted information.

27. - A system as per any of claims 23 to 25, wherein said central server (Sc) is also intended for carrying out the actions of the method as per any of claims 2, 3, 4 and

5.