LU500967B1

LU500967B1 - Method and system for vulnerable road user clustering

Info

Publication number: LU500967B1
Application number: LU500967A
Authority: LU
Inventors: Friedbert Berens
Original assignee: Fbconsulting S A R L
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2023-06-07
Also published as: EP4445357A1; WO2023104871A1

Abstract

The proposed invention allows for reliable estimation of the position of devices associated with vulnerable road users, VRU, in an intelligent transport system, ITS, communication network. Moreover, the invention provides means for managing a VRU cluster with high positioning accuracy based on ultra-wideband, UWB, communications and based on the reuse of other communication means to participate in safety-critical data exchanges. High-precision data of vulnerable road users is made available, notably through the use of ultra-wide band positioning techniques.

Description

METHOD AND SYSTEM FOR VULNERABLE ROAD USER CLUSTERING LU500967

Technical field

The invention lies in the field of communication systems. In particular, the invention relates to a method and system for estimating and gathering precise position information of vulnerable road users in a collaborative intelligent transport system network.

Background of the invention

In a cooperative intelligent transport system, C-ITS, vehicles are essentially network nodes that exchange information among themselves and/or with road-side infrastructure equipment, with the goal to improve the awareness of the different traffic participants among all nodes of the network.

Such systems include for example vehicular networks. Known C-ITS systems use wireless communication protocols based on IEEE 802.11p, IEEE 802.11bd, LTE-V2X or 5G-NR and higher layer protocols defined in ETSI TC ITS and IEEE 1609 standard documents. While positioning information is often sufficiently precise at a granularity of meters for vehicles such as cars, when vulnerable road users, VRU, such as cyclists or pedestrians are concerned, a higher accuracy is desirable. In comparison with a road user who drives a car, a pedestrian is more vulnerable when impacted by the car, than the driver. Moreover, the displacement direction of vulnerable road users is prone to change abruptly, as theses road users are often not limited by the directions/speeds imposed by the road infrastructure or the prevailing traffic signalling. À positioning error of 1 m may for example erroneously indicate that a VRU is located on a sidewalk along a road, when the VRU is really on the road that is shared with larger vehicles. In order to be able to include pedestrians and other vulnerable road users into a safety-related communication system, specific ITS services and protocol-level messages are required set to efficiently and accurately support the communication of VRUs with vehicles and infrastructure.

In particular, a high level of positioning accuracy down to 25 cm and below is desirable.

Moreover, if a large number of pedestrians participate in a safety related communication network, the information they relay to other nodes in the network potentially uses a large part of the available communication resources.

Technical problem to be solved

It is an objective of the invention to present a method, which overcomes at least some of the disadvantages of the prior art.

Summary of the invention

In accordance with a first aspect of the invention, a method for clustering Vulnerable Road User,

VRU, position data in an intelligent transport system, ITS, at a first portable device associated with a first VRU if provided. The first portable device has first means for transmitting and receiving data to/from nodes of an I'TS network, and second means for transmitting and receiving LU500967 ultra-wideband signals. The method comprises the steps of: - using detection means, detecting at least one second VRU:; - estimating position information of the detected at least one second VRU relative to the first portable device using ultra-wideband ranging signals; - if the estimated position information satisfies a set of predetermined conditions, transmitting position data indicative of said estimated position information of the detected at least one second VRU from the first portable device to a node of said ITS network.

In accordance with another aspect of the invention, a method for clustering Vulnerable Road

User, VRU, position data in an intelligent transport system, ITS, at a node of the ITS network is provided. The network node has first means for transmitting and receiving data to/from peer nodes of the ITS network, and second means for transmitting and receiving ultra-wideband signals. The method comprises the steps of: - using detection means, detecting at a plurality of VRUs; - estimating position information of the detected at VRUs relative to the ITS network node using ultra-wideband ranging signals; - if the estimated position information satisfies a set of predetermined conditions, transmitting position data indicative of said estimated position information of the detected VRUs from the ITS network node to at least one peer node in said ITS network.

The first means for transmitting and receiving data to/from nodes of an ITS network may preferably comprise a WiFi, LTE-V2X, 5G-NT V2X, 802.11bd or Bluetooth, preferably

Bluetooth Low Energy, transceiver.

Preferably, the step of estimating position information of the detected at least one second VRU may comprise the preliminary step of: - estimating coarse position information of the detected at least one second VRU relative to the first portable device using the first means for transmitting and receiving data: followed by - estimating precise position information of the detected at least one second VRU relative to the first portable device using the second means for transmitting and receiving ultra-wideband signals. Preferable, the ultra-wideband signals may comprise ultra-wideband ranging signals.

The method may further preferably comprise the step of transmitting data to a device associated with said second VRU, indicating that said second VRU should not transmit position data to nodes of the ITS network.

The step of detecting at least one second VRU may preferably comprise receiving data from a LU500967 device associated with said second VRU using said first means for transmitting and receiving data to/from nodes of an ITS network.

Preferably, the step of detecting at least one second VRU may comprise using ultra-wideband ranging signals transmitted and received using said second means for transmitting and receiving ultra-wideband signals.

The step of estimating position information of the detected at least one second VRU relative to the first portable device may preferably comprise estimating a relative displacement direction and a relative displacement speed.

Preferably, the set of predetermined conditions may comprise the condition that the estimated relative displacement direction of the detected at least one second VRU substantially corresponds to the displacement direction of the first portable device.

The set of predetermined conditions may preferably the condition that the estimated relative displacement speed of the detected at least second VRU substantially corresponds to the displacement speed of the first portable device.

The displacement direction and/or the displacement speed of the first portable device may be estimated by the first portable device using any of Global Positioning Satellite System receiver, a gyroscope or an accelerometer, or any combination thereof.

Preferably, the position data transmitted from the first portable device to a node of said ITS network may comprise position information indicative of the position of the first portable device and of the at least one second VRU.

The method may preferably further comprise the step of computing an absolute position of the at least one second VRU using absolute position information of the first portable device and the estimated relative position information.

Further, the method may preferably comprise the step of transmitting said absolute position to a device associated with said at least one second VRU using either of the first or second data transmission means.

The method may further preferably comprise the preliminary step of switching the first portable LU500967 device from first operating mode to a second operating mode, upon reception of a predetermined signal from a node of said ITS network.

Preferably, the first operating mode may be a power saving mode, in which a least said seconds means for transmitting and receiving ultra-wideband signals are not operational, and the first portable device may preferably be fully operational in said second operating mode.

According to another aspect of the invention, a computing device is provided. The computing device comprises a data processor, a memory element, first means for transmitting and receiving data to/from nodes of an ITS network, and second means for transmitting and receiving ultra- wideband signals. The data processor is configured for: - upon detection of at least one Vulnerable Road User, VRU, in said ITS network, estimating position information of the at least one VRU relative to the computing device itself using ultra-wideband ranging signals; - if the estimated position information satisfies a set of predetermined conditions, transmitting position data indicative of said estimated position information of the detected at least one second VRU from the computing device to a node of said ITS network.

Preferably, the data processor may further be configured to implement the method in accordance with aspects of the invention.

The computing device may preferably be a portable computing device that is associated with a

Vulnerable Road User, VRU, in said ITS network.

In accordance with a further aspect of the invention, an intelligent transport system, ITS, communication network is provided. The ITS communication network comprises at least one computing device associated with a first Vulnerable Road User, VRU, according to aspects of the invention. At least one node of the communication network is configured for receiving estimated position information of at least a first and a second Vulnerable Road User, VRU, from said at least one computing device.

In accordance with yet another aspect of the invention, a computer program comprising computer readable code means is provided, which, when run on a computer system, causes the computer system to carry out the method according to aspects of the invention.

In accordance with a final aspect of the invention, a computer program product comprising a LU500967 computer readable medium on which the computer program according an aspect of the invention is stored. 5 The method provided by aspects of the invention allows for reliable estimation of the position of devices associated with vulnerable road users in an intelligent transport system communication network. Moreover, the invention provides means for managing a VRU cluster with the required positioning accuracy based on a UWB communication and on the reuse of other communication means to participate in the safety related ITS communication. High-precision data of vulnerable road users is made available, notably through the use of ultra-wide band positioning techniques.

A device that is associated with a VRU may detect, for example using UWB ranging signals and data exchanges with nearby devices, that several VRUs share similar position features such as movement direction or displacement speed. This detection can be made, and the corresponding conclusions can be draw, without the use of ITS infrastructure nodes, but by relying on direct ad- hoc network capabilities among neighbouring VRUs. It becomes possible to aggregate the data describing such a group or cluster of VRUs that share a similar positioning pattern at a cluster delegate node. The cluster delegate node then communicates with other nodes of the communication network. This reduces the spectrum resource usage and the processing requirements at the receiver. A combination of ad-hoc possibilities among devices associated with VRUs on the one hand, and infrastructure-supported communication and positioning means on the other hand, allows for efficiently dissemination of safety-critical information to VRUs participating in the collaborative intelligent transport system network.

Brief description of the drawings

Several embodiments of the present invention are illustrated by way of figures, which do not limit the scope of the invention, wherein: - Figure 1 shows a workflow indicating the main steps of a method in accordance with a preferred embodiment of the invention; - Figure 2 shows an intelligent transport network including a device in accordance with a preferred embodiment of the invention; - Figure 2 shows an intelligent transport network including a device in accordance with a preferred embodiment of the invention.

Detailed description of the invention

This section describes the invention in further detail based on preferred embodiments and on the figures. Similar reference numbers will be used to describe similar or the same concepts throughout different embodiments of the invention. For example, references 100 and 200 respectively denote two different embodiments of a device in accordance with aspects of the LUS00967 invention, for implementing embodiments of the method in accordance with the invention.

It should be noted that features described for a specific embodiment described herein may be combined with the features of other embodiments unless the contrary is explicitly mentioned.

Features commonly known in the art will not be explicitly mentioned for the sake of focusing on the features that are specific to the invention. For example, the disclosed computing device is evidently powered by an electric power supply, such as a battery, even though this is not explicitly shown in the figures.

Figure 1 illustrates the main steps 01, 02 and 03 in accordance with a preferred embodiment of the invention, while Figure 2 provides an illustration of the method steps, and of a device 100 in accordance with a preferred embodiment of the invention.

An intelligent transport system, ITS, network 1000 comprises a plurality of networked nodes 100°, implemented by computing devices that equip car, road infrastructure elements such as traffic lights, or other signalling device. The data communication channels between nodes 100° are either wired large area network connections such as Ethernet connections, or WiFi wireless network connections. The nodes may also use a cellular data communication infrastructure, such as 4G or 5G to communicate data among themselves. The aim of the ITS network is to provide time sensitive and security sensitive information about a traffic state to critical nodes of the network. For example, vehicles may communicate among themselves to avoid crashes, or a vehicle may receive an order to urgently break due to a cyclist or pedestrian approaching in a dead angle. As such, the use of the ITS allows to improve the overall traffic safety, by reacting and adapting to both local and large-scale traffic events. A particular node of the ITS network 1000 is provided by a portable device 100 associated with a first vulnerable road user, VRU, 10.

While the VRU 10, is depicted as a pedestrian, the VRU may as well be a cyclist, or motorcyclist, without limiting the invention thereto. The portable device 100 may be a dedicated device that is carried by the VRU 10, a wearable device such as a smartwatch, or a smartphone, without limiting the invention to these examples. The portable device 100 comprises first means for transmitting and receiving data 110 to and from other nodes 100” of the ITS. The first means for transmitting and receiving data 110 may for example comprise a WiFi or cellular data networking interface such as they are well known in the art, adapted for communicating wirelessly with the nodes 100° of the ITS network. The portable device 100 further comprises second means for transmitting and receiving ultra-wideband signals 120.

At a first step 01 of the proposed method, at least one second VRU 20 is detected using detection means 130 of the portable computing device 100. The detection means may, by way of non-

limiting example comprise dedicated sensors such as a radar signal transceiver, a camera, or they LU500967 may also comprise any of the first and second data transmission means 110, 120. The operation of the detection means 130 is governed by a data processor 140, which is preferably programmed accordingly by appropriate computer software code.

At a second step 02, the position of the second VRU 20 relative to the portable device 100 1s estimated with the help of ultra-wideband, UWB, ranging signals, or by using UWB ranging signals exclusively.

If the estimated position information satisfies a set of predetermined conditions, data that is indicative of the estimated position information P(20) of the detected at least one second VRU 20 is transmitted from the portable device 100 to a node 100” of the ITS network. This corresponds to step 03 of as shown in figure 1. Preferably, both position data about the device 100 itself, and about the at least one second VRU 20 are transmitted.

The portable computing device 100 may detect several second VRUs, as shown for example by

VRU 20 and 20° in figure 2. The position information may comprise an estimated relative position P(20), P(20”) with respect to the device 100, as well as a displacement speed and direction v(20), v(20”). The set of predetermined conditions, which may for example be stored in the memory element 150 to which the data processor 140 has read/write access, preferably comprises any of the following conditions, in isolation or in combination: - the position of a detected VRU is with three to five meters of the position of the device 100; - the displacement speed is within 5% of the displacement speed of the device 100.

The memory element 150 may preferably be a random-access memory, RAM, module, but any known memory element may be used, including a hard disk drive, HDD, or solid-state drive,

SDD, without the invention being limited to these examples. The data processor may be an application specific integrated circuit, or a general-purpose processing unit programmed appropriately.

If the set of predetermined conditions is satisfied, the correspondingly detected VRUs 20, 20° position information is clustered at the device 100 and clustered data is transmitted, preferably in a single data packet, to a node 100” of the ITS network. It becomes apparent that the more VRUs are identified as belonging to a group or cluster, because they satisfy the set of predetermined conditions, the more communication resources are preserved. Only one data transmission from the device 100 to the ITS network is sufficient to provide precise information describing the positions of a plurality of VRU cluster members. If the detected VRU do not participate actively in the ITS network, for lack of corresponding computing devices, the method allows to integrate information about these real but unconnected traffic users into the ITS network, thus enriching the data set available to the ITS network. If at any point in time, the set of predetermined conditions is no longer satisfied for a given second VRU 20, it is immediately excluded from the LU500967 cluster, and its position information P(20) is no longer transmitted by the computing device 100.

In addition to the position and the estimated displacement speed of cluster members, the position data P(10), P(20) transmitted may be complemented by further data. For example, a shape of the cluster may be communicated to the ITS network. This allows nodes of the ITS network to consider all VRUs in the cluster a shape having a common position, displacement speed and/or direction. Alternatively, or additionally, the number and type (cyclist, pedestrian, ...) of detected

VRUs may be included in the position information.

The use of ultra-wideband, UWB, signalling in the step of estimating a detected VRU”s position allows for the provision of precise positioning data. In an UWB transmitter such as the transceiver 120, information may be transmitted by generating radio pulses that occupy a large bandwidth at specific time intervals. The information may for example be modulated on UWB pulses by encoding the polarity of the pulse, its amplitude and/or by using orthogonal pulses.

UWB pulses can be sent sporadically at relatively low pulse rates to support time or position modulation but can also be sent at rates up to the inverse of the UWB pulse bandwidth.

Alternatively, information may be modulated using Orthogonal Frequency Division

Multiplexing, OFDM, Fast Frequency Hopping, Frequency-modulated continuous-wave, FMCW, or other known modulation techniques.

An UWB transmission system may further be used to determine the time of flight of a transmitted

UWB signal at various frequencies. This helps overcome multipath propagation, as at least some of the frequencies have a line-of-sight trajectory. Using time of flight methods, distances to objects, obstacles or Vulnerable Road Users in the vicinity of an UWB transceiver 120 can be measured to high resolution and accuracy. The measurement of distances also implies the detection of the objects, obstacles or Vulnerable Road Users to which the distances are being measured. As such the transceiver 120 may be considered as being part of the detection means 130. Using similar techniques, several UWB transceivers that are within communication range of cach other, for example several VRUs, each equipped with their own portable device 100, may also be configured to measure the distances between themselves, thereby enabling for example one UWB device to estimate the relative position or location of a second UWB device. The existing access layers in ITS networks, including ITS-G5 based on the IEEE802.11p standard, use a bandwidth of 10MHz, whereas UWB uses at least a bandwidth of 500MHz. In general, it can be assumed that the positioning capability of UWB is at least 50 time better than the capability of existing ITS systems. Moreover, data traffic may be handled by the UWB transceiver 120 as well.

In an alternative embodiment, the method steps that have been described are implemented at a LU500967 node of an ITS network, that is not associated with a VRU. It may for example be a part of the road and signalling infrastructure, such as a traffic light. The node detects a plurality of VRUs in its vicinity and estimates their position relative to the node itself, as previously described. If a subset or all of the detected VRUs satisfy a set of predetermined conditions, their position data is clustered and notified to other nodes of the ITS network. Ideally, the corresponding VRUs are notified so that they stop communicating directly with the ITS network themselves. In this embodiments, additional sensors that are available in the fixed node infrastructure, may be used to complement the position data that is estimated by the ITS network node. These may for example include traffic cameras, or absolute geopositioning means. The ITS network node that implements the method in accordance with the invention may be considered to be a “virtual”

VRU cluster member: while it is not itself associated with a vulnerable road user, it implements a

VRU position data clustering method.

Figure 3 provides an illustration of another preferred embodiment of the invention. The depicted system shares many similarities with the system described in the context of figure 2.

An intelligent transport system, ITS, network 2000 comprises a plurality of networked nodes 200°, of which only one is shown. The aim of the ITS network is to provide time sensitive and security sensitive information about a traffic state to critical nodes of the network. A particular node of the ITS network 3000 is provided by a portable device 200 associated with a first vulnerable road user, VRU, 10. While the VRU 10, is depicted as a pedestrian, the VRU may as well be a cyclist, or motorcyclist, without limiting the invention thereto. The portable device 200 may be a dedicated device that is carried by the VRU 10, a wearable device such as a smartwatch, or a smartphone, without limiting the invention to these examples. The portable device 200 comprises first means for transmitting and receiving data 210 to and from other nodes 200’ of the ITS network. The first means for transmitting and receiving data 210 may for example comprise a WiFi or cellular data networking interface such as they are well known in the art, adapted for communicating wirelessly with the nodes 200’ of the ITS network. The portable device 200 further comprises second means for transmitting and receiving ultra-wideband signals 220.

At a first step 01 of the proposed method, at least one second VRU 20, who is equipped with a device 201 that participates in the ITS network 2000, is detected using detection means 230 of the portable computing device 200. The device 201 may be similar to the device 200. The detection means may, by way of non-limiting example comprise dedicated sensors such as a radar signal transceiver, a camera, or they may also comprise any of the first and second data transmission means 210, 220. The operation of the detection means 230 is governed by a data processor 240,

which is preferably programmed accordingly by appropriate computer software code. Typically, LU500967 both the device 200 and the device 201 will transmit position data to the ITS network nodes 200” independently. As such, the detection of VRU 20 at the device 200 associated with the first VRU 10 may be a passive operation from the point of view of the portable device 200. À coarse location or position information may be estimated from data packets that are broadcast by the device 201 associated with the second VRU 20 over the data communication channels of the ITS network. As such, the device 200, using the first data reception means 210, may detect the presence, and get coarse position information R(20), of the device 201 through a data packet received wither directly from the device 201 or through an intermediary network node 200’ of the

ITS network. This event may trigger an investigation of precise position information of the second VRU in the following step.

At a second step 02, the precise position of the second VRU 20 and device 201 relative to the portable device 200 is estimated with the help of ultra-wideband, UWB, ranging signals, or by using UWB ranging signals exclusively.

If the estimated position information satisfies a set of predetermined conditions, data that is indicative of the estimated position information P(20) of the detected at least one second VRU 20 and device 201 is transmitted from the portable device 200 to a node 200’ of the ITS network.

This corresponds to step 03 of as shown in figure 1. Preferably, both position data about the device 200 itself, and about the at least one second VRU 20 and device 201are transmitted.

The portable computing device 200 may detect several second VRUs. The position information may comprise an estimated relative position with respect to the device 200, as well as a displacement speed and direction. The set of predetermined conditions, which may for example be stored in the memory element 250 to which the data processor 240 has read/write access, preferably comprises any of the following conditions, in isolation or in combination: - the position of a detected VRU is with three to five meters of the position of the device 200; - the displacement speed is within 5% of the displacement speed of the device 200.

If the set of predetermined conditions is satisfied, the correspondingly detected VRUs 20, 20° position information is clustered at the device 200 and clustered data is transmitted, preferably in a single data packet, to a node 200’ of the ITS network. The device 201 is notified, preferably via

UWB or WiFi data transmission, that it should stop communicating its own position to the ITS nodes 200°. This allows the device 201 to save power that would otherwise be drawn from its limited battery. It further becomes apparent that the more VRUs are identified as belonging to a group or cluster, because they satisfy the set of predetermined conditions, the more communication resources are preserved. Only one data transmission from the device 200 to the

ITS network is sufficient to provide precise information describing the positions of a plurality of LU500967

VRU cluster members. If at any point in time, the set of predetermined conditions is no longer satisfied for a given second VRU 20, it is immediately excluded from the cluster, and its position information P(20) is no longer transmitter by the computing device 200. The ITS network, having acquired knowledge about the nature and number of VRUs in the cluster, may also address specific data transmissions to devices 201 associated with particular VRUs, if required. Such communications may be centralized through the device 200, which may act as a router or relay within the ad-hoc network formed by the VRUs it has detected and clustered, in order to forward the corresponding data to the device 201 associated with the destination VRU 20.

In addition to the position and the estimated displacement speed of cluster members, the position data P(10), P(20) transmitted may be complemented by further data. For example, a shape of the cluster may be estimated by the data processor 240 based on estimated positions of detected VRU and communicated to the ITS network. This allows nodes of the ITS network to consider all

VRUs in the cluster a shape having a common position, displacement speed and/or direction.

Alternatively, or additionally, the number and type (cyclist, pedestrian, ...) of detected VRUs may be included in the position information.

In all embodiments, the device 100, 200 in accordance with the invention may further be configured to operate in either of two states. In a first, power saving state, no ranging signals are emitted using the UWB transmission means 120, 220. If the device receives a predetermined packet type on any wireless receiving interface, such as a WiFi networking interface or the ITS receiving interface 110, 210, it will wake up and switch from the first operating mode into a second operating mode. In the second operating mode, second VRUs are detected and their positions are estimated as described here above. The limited power resources of the device 100, 200 are thus saved and used only in situations in which the ITS network 1000, 2000 deems it necessary to obtain precise clustering information about Vulnerable Road Users. For example, an

ITS network node 100°, 200” associated with a traffic light on a busy road crossing may broadcast a predetermined “wake-up” data packet to devices 100, 200, which will start detecting

VRUs in their vicinity as preciously described. The second operation mode may preferably be switched off after a predetermined time, so that the device 100, 200 will not detect VRU in non- critical traffic situations. Preferably, wake-up data packets are signed using a cryptographic key, so that the identity of an authentic and trusted sender being part of the same trusted domain as the device can be verified. The configuration of the device 100, 200 is such that only wake-up data packets bearing a verified signature produced by a trusted sender initiate a switch from the power saving operation mode to the functional operation mode. Alternatively, or in addition, wake-up data packets are encrypted using private keys associated with the issuing nodes 100°, 200” of the

ITS network. As such, only certified and authenticated nodes 100°, 200” covered by a public key infrastructure that also covers the device 100, 200, may wake the device 100, 200 up to switch LU500967 from the first operating mode into the second operating mode. The device 100, 200 1s unable to react to the received data packet, unless the corresponding public key 1s available to the device 100, 200 for decrypting the wake-up message.

A skilled person will be enabled by the present description and the accompanying figures to provide a computer program code for implementing the described functionalities without undue burden and without exercising inventive skill.

It should be understood that the detailed description of specific preferred embodiments is given by way of illustration only, since various changes and modifications within the scope of the invention will be apparent to the person skilled in the art. The scope of protection is defined by the following set of claims.

Claims

Claims LU500967

1. A method for clustering Vulnerable Road User, VRU, position data in an intelligent transport system network (1000, 2000), ITS, at a first portable device (100, 200) associated with a first VRU (10), the first portable device having first means for transmitting and receiving data (110, 210) to/from nodes (100°, 200’) of an ITS network, and second means for transmitting and receiving ultra-wideband signals (120, 220), comprising the steps of: - using detection means (130, 230), detecting (01) at least one second VRU (20); - using data processing means (140, 240), estimating position information (02) of the detected at least one second VRU (20) relative to the first portable device (100, 200)) using ultra-wideband ranging signals; - if the estimated position information satisfies a set of predetermined conditions, transmitting position data (03) indicative of said estimated position information P(20) of the detected at least one second VRU (20) from the first portable device (100, 200) to a node (100°, 200°) of said ITS network.

2. The method according to claim 1, wherein the step (02) of estimating position information of the detected at least one second VRU comprises the preliminary step of: - estimating coarse position information R(20) of the detected at least one second VRU (20) relative to the first portable device(200) using the first means for transmitting and receiving data (210); followed by - estimating precise position information of the detected at least one second VRU relative to the first portable device using the second means (220) for transmitting and receiving ultra-wideband signals.

3. The method according to any of claims 1 or 2, further comprising the step of transmitting data to a device (201) associated with said second VRU (20), indicating that said second VRU should not transmit position data to nodes (2007) of the ITS network.

4. The method according to any of claims 1 to 3, wherein the step of detecting at least one second VRU comprises receiving data from a device (201) associated with said second VRU (20) using said first means for transmitting and receiving data (210) to/from nodes of an ITS network.

5. The method according to any of claims 1 to 3, wherein the step of detecting at least one second VRU (20) comprises using ultra-wideband ranging signals transmitted and received using said second means for transmitting and receiving ultra-wideband signals LU500967 (120, 220).

6. The method according to any of claims 1 to 5, wherein the step of estimating position information of the detected at least one second VRU (20) relative to the first portable device (100, 200) comprises estimating a relative displacement direction and a relative displacement speed.

7. The method according to claim 6, wherein the set of predetermined conditions comprises the condition that the estimated relative displacement direction of the detected at least one second VRU (20) substantially corresponds to the displacement direction of the first portable device (100, 200).

8. The method according to any of claims 6 or 7, wherein the set of predetermined conditions comprises the condition that the estimated relative displacement speed of the detected at least second VRU (20) substantially corresponds to the displacement speed of the first portable device (100, 200).

9. The method according to any of claims 1 to 8, wherein the position data transmitted from the first portable device (100, 200) to a node (100°, 200”) of said ITS network comprises position information indicative of the position of the first portable device P(10) and of the at least one second VRU P(20).

10. The method according to any of claims 1 to 9, further comprising the step of computing an absolute position of the at least one second VRU (20) using absolute position information of the first portable device (100, 200) and the estimated relative position information.

11. The method according to claim 10, further comprising the step of transmitting said absolute position to a device (201) associated with said at least one second VRU (20) using either of the first (210) or second (220) data transmission means.

12. The method according to any of claims 1 to 11, further comprising the preliminary step of switching the first portable device (100, 200) from first operating mode to a second operating mode, upon reception of a predetermined signal from a node (100°, 200’) of said ITS network.

13. The method according to claims 12, wherein said first operating mode is a power saving LU500967 mode, in which a least said seconds means for transmitting and receiving ultra-wideband signals are not operational, and wherein the first portable device if fully operational in said second operating mode.

14. A computing device (100, 200) comprising a data processor (140, 240), a memory element (150, 250), first means for transmitting and receiving data (110, 210) to/from nodes (100°, 200°) of an ITS network (1000, 2000), and second means for transmitting and receiving ultra-wideband signals (120, 220), wherein the data processor is configured for: - upon detection of at least one Vulnerable Road User, VRU, (20) in said ITS network, estimating position information of the at least one VRU relative to the computing device itself (100, 200) using ultra-wideband ranging signals; - if the estimated position information satisfies a set of predetermined conditions, transmitting position data indicative of said estimated position information of the detected at least one second VRU (20) from the computing device (100, 200) to a node (100°, 200”) of said ITS network.

15. The computing device according to claim 14, wherein the data processor (140, 240) is further configured to implement the method in accordance with any of claims 2 to 13.

16. The computing device according to any of claims 14 or 15, wherein the computing device is a portable computing device (100, 200) that is associated with a Vulnerable Road User, VRU, (10) in said ITS network.

17. An intelligent transport system, ITS, communication network (1000, 2000) comprising at least one computing device (100, 200) according to any of claims 14 to 16, associated with a first Vulnerable Road User, VRU, (10) wherein at least one node (100°, 200°) of the communication network is configured for receiving estimated position information of at least a first and a second Vulnerable Road User, VRU, (20) from said at least one computing device (100, 200).

18. A computer program comprising computer readable code means, which, when run on a computer system, causes the computer system to carry out the method according to any of claims 1 to 13.

19. A computer program product comprising a computer readable medium on which the LUS00967 computer program according to claim 18 1s stored.