ETSI TS 101 539-2 V1.1.1 (2018-06)

TECHNICAL SPECIFICATION
Intelligent Transport Systems (ITS);
V2X Applications;
Part 2: Intersection Collision Risk Warning (ICRW)
application requirements specification

2 ETSI TS 101 539-2 V1.1.1 (2018-06)

Reference
DTS/ITS-0010015
Keywords
application, interoperability, ITS
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3 ETSI TS 101 539-2 V1.1.1 (2018-06)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 6
4 Conforming ITS-S performance class definition . 7
5 Intersection Collision Risk Warning application overview . 8
5.1 ICRW in the ITS architecture . 8
5.1.1 Overview . 8
5.1.2 Crossing collision warning . 10
5.1.3 Traffic sign violation warning . 11
5.2 ICRW originating mode functionalities . 14
5.2.1 CAM transmission . 14
5.2.2 DENM transmission: signalling of a traffic sign violation risk . 14
5.2.3 DENM transmission: signalling of an intersection collision risk . 14
5.2.4 Interaction with other ITS-S layers . 14
5.3 ICRW receiving mode functionalities . 15
5.3.1 Detection of risk . 15
5.3.1.1 Traffic sign violation risk detection . 15
5.3.1.2 Intersection collision risk detection . 15
5.3.2 Application priority management . 15
5.3.3 Issuing warning to vehicle driver . 16
6 Application functional requirements . 16
6.1 Introduction . 16
6.2 Crossing collision risk detection requirements . 16
6.3 Traffic sign violation detection requirements . 17
6.4 Warning triggering requirements . 18
6.5 DENM transmission requirements . 18
6.6 Message processing requirements . 20
7 Application operational requirements . 21
7.1 Introduction . 21
7.2 Security and reliability requirements . 21
7.3 System minimum performance requirements . 21
7.3.1 Event position accuracy . 21
7.3.2 Communication coverage . 21
7.3.3 System end to end latency time . 22
7.3.4 Message processing . 22
Annex A (informative): CAMs interval adjustment based on critical safety situation . 23
Annex B (informative): Application state machine . 24
Annex C (informative): Safety Shield . 26
Annex D (informative): Driver HMI considerations . 28
Annex E (informative): Bibliography . 29
History . 30

ETSI
4 ETSI TS 101 539-2 V1.1.1 (2018-06)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Intelligent Transport Systems
(ITS).
The present document is part 2 of a multi-part deliverable. Fulls details of the entire series can be found in part 1 [i.4].
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
5 ETSI TS 101 539-2 V1.1.1 (2018-06)
1 Scope
The present document provides Intersection Collision Risk Warning Application requirements and specifies the
necessary parameters and conditions to operate the application using CAM [1], DENM [2] and the intersection service
messages [4]. It includes the specifications of functional requirements and operational requirements of the LCRW
application.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 302 637-2 (V1.3.2): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[2] ETSI EN 302 637-3 (V1.2.2): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Part 3: Specifications of Decentralized Environmental Notification
Basic Service".
[3] ETSI TS 101 539-3 (V1.1.1): "Intelligent Transport Systems (ITS); V2X Applications; Part 3:
Longitudinal Collision Risk Warning (LCRW) application requirements specification".
[4] ETSI TS 103 301 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Facilities layer protocols and communication requirements for
infrastructure services".
[5] ETSI TS 102 636-4-2 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
GeoNetworking; Part 4: Geographical addressing and forwarding for point-to-point and point-to-
multipoint communications; Sub-part 2: Media-dependent functionalities for ITS-G5".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TR 102 638: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of
Applications; Definitions".
[i.2] ETSI EN 302 665 (V1.1.1): "Intelligent Transport Systems (ITS); Communications Architecture".
[i.3] ETSI TS 102 894-1 (V1.1.1): "Intelligent Transport Systems (ITS); Users and applications
requirements; Part 1: Facility layer structure, functional requirements and specifications".
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6 ETSI TS 101 539-2 V1.1.1 (2018-06)
[i.4] ETSI TS 101 539-1 (V1.1.1): "Intelligent Transport Systems (ITS); V2X Applications; Part 1:
Road Hazard Signalling (RHS) application requirements specification".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
age of data: difference between the time of a data element value setting at the originating ITS-S and the time the same
data element value is used to undertake an appropriate action at a receiving ITS-S
NOTE: The age of data is an important quality parameter reflecting the freshness of highly dynamic data
elements in particular when a collision risk is assessed at vehicles' receiving levels.
conflict zone: zone of an intersection where the trajectory paths of vehicles and other traffic participants
(e.g. pedestrian, bicycles, vehicles) may cross
primary road safety application: ITS-S application which purpose is to prevent a collision
stop line: pavement marking line extending across lanes to indicate the point at which a stop is intended or required to
be made
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
BSA Basic Set of Applications
CA Co-operative Awareness
CAM Co-operative Awareness Message
CCH Control Channel
DCC Decentralized Congestion Control
DEN Decentralized Environmental Notification
DENM Decentralized Environmental Notification Message
HMI Human Machine Interface
ICRW Intersection Collision Risk Warning
ITS Intelligent Transport Systems
ITS-S ITS Station
IVI Infrastructure to Vehicle Information
IVIEM In Vehicle Information Extended Message
IVIM Infrastructure to Vehicle Information Message
LCRW Longitudinal Collision Risk Warning
MAPEM Message with detailed road topology information used by RLT service
MAT Maximum Action Time
MDRT Maximum Driver Reaction Time
MLT Maximum Latency Time
OEM Original Equiment Manufacturer
OR Operational Requirements
RHS Road Hazard Signalling
RLT Road and Lane Topology
SPAT Signal Phase And Timing
SPATEM Signal Phase And Timing Extended Message
TLM Traffic Light Maneuver
TTC Time To Collision
VRU Vulnerable Road User
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7 ETSI TS 101 539-2 V1.1.1 (2018-06)
4 Conforming ITS-S performance class definition
Intersection Collision Risk Warning (ICRW) application is considered as a primary road safety application. As
introduced in clause 4 of ETSI TS 101 539-3 [3], primary road safety applications are ITS applications that target at
reducing the risk of collision and thus improving the road safety. An ICRW application provides intersection collision
risk warning to drivers. The warning indicates the risk of potential intersection collision risk that requires an immediate
action of the driver.
NOTE: It is not excluded to implement the ICRW with automatic assistance system, such as automatic braking
system. In this case, the automatic assistance system will react directly on the braking system for the
driver, enabling a quicker reaction towards the collision risk.
The ICRW application relies on the processing of Cooperative Awareness Message (CAM) as specified in ETSI
EN 302 637-2 [1] and Decentralized Environmental Notification Message (DENM) as specified ETSI EN 302 637-3 [2]
transmitted from vehicle ITS-Ss or road side ITS-S. If applicable, an ICRW application may in addition rely on the
roadside infrastructure services such as Traffic Light Maneuver (TLM) service, Road and Lane Topology (RLT) service
and Infrastructure to Vehicle Information (IVI) service as specified in ETSI TS 103 301 [4]. These messages enable a
receiving vehicle ITS-S be informed of the movement status of other vehicles in the intersection as well as the traffic
light status, intersection access priority status, and topology of the intersection. This receiving ITS-S is therefore able to
estimate the potential collision risk and inform driver when necessary.
The ICRW application requires a short end-to-end latency time. This latency time is the time difference between T0 and
T6 and shall be as defined in ETSI TS 101 539-3 [3] and illustrated in Figure 1, in order to provide timely warning to
driver. T0 is denoted as time at which the vehicle data is available at the vehicle electronic systems. For message
transmitted from road side ITS-S, T0 is denoted as time at which the data is available at data source e.g. traffic light
status data available at traffic light controller system. T6 is denoted as time at which the warning is presented on the
vehicle HMI or time at which a direct action is requested to the vehicle electronic system, if applicable. Typically,
300 ms end to end latency time is required.

Figure 1: Application end to end latency time
In particular, time difference from T0 to T1 reflects the freshness of the data provided by a message with regards to the
message time stamp. ETSI TS 101 539-3 [3] has defined two performance classes (class A and class B) based on this
time difference, indicating the capability of a vehicle ITS-S to provide up-to-date information in CAM and DENM
within a threshold value (e.g. 150 ms).
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8 ETSI TS 101 539-2 V1.1.1 (2018-06)
Road side ITS-S mounted within an intersection provides up-to-date information on intersection traffic light status
(SPATEM), road topology (MAPEM) and infrastructure to vehicle Information (IVIM) in order to enable the receiving
ITS-S be informed about the allowed maneuvers, the access rights to execute the maneuvers (e.g. "green", "yellow",
"red"). The freshness of road side information may vary depending on the information update rate. Typically, such
update rate is configured by road side ITS-S application, as described in ETSI TS 103 301 [4].
5 Intersection Collision Risk Warning application
overview
5.1 ICRW in the ITS architecture
5.1.1 Overview
The objective of an ICRW application is to detect potential collision risk between two or more vehicles or obstacles
inside an intersection area. In addition, the ICRW may detect potential traffic sign violation at an intersection area.
When a collision risk or traffic sign violation risk is detected, the vehicle may issue a warning to the driver.
If the collision risk is detected by the roadside ITS-S, it may trigger the transmission of corresponding collision risk
warning DENM to approaching vehicles. A vehicle receiving such DENM may issue a warning to driver, when the
information is estimated relevant. One example use case is that a road side ITS-S equipped with sensors capable of
detecting the intersection collision risk or traffic sign violation risk may transmit an intersection collision risk warning
DENM to vehicles approaching to or inside the intersection area.
ICRW is an application layer entity that implements at least one intersection collision risk use case. In one possible
implementation, an ICRW may implement more than one intersection collision risk use cases into one ITS-S application
entity. The present document does not specify any implementation structure of the ICRW application.
Figure 2 presents an ICRW application in the ITS-S architecture as defined in ETSI EN 302 665 [i.2] as well as its
logical interfaces with other entities and layers.
ICRW
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Figure 2: ICRW and logical interfaces
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9 ETSI TS 101 539-2 V1.1.1 (2018-06)
The ICRW application functionalities are distributed in conforming ITS-Ss. The following functional modes of the
application are included:
• Vehicle ITS-S originating mode: This mode refers to functionalities implemented by a vehicle ITS-S,
including the triggering of DENM transmission as specified in ETSI EN 302 637-3 [2] upon the detection of
an intersection collision risk or traffic sign violation risk, and the transmission of CAM according to the CAM
transmission rules as specified in ETSI EN 302 637-2 [1]. Some functional requirements are provided in ETSI
TS 102 894-1 [i.3] for traffic situations which may be leading to an intersection collision.
• Minimum Vehicle ITS-S receiving mode: This mode refers to functionalities implemented by a vehicle ITS-S,
including the processing of received ICRW DENM and providing warning to the driver in case based on the
evaluation of the DENM.
• Full Vehicle ITS-S receiving mode: This mode refers to functionalities implemented by a vehicle ITS-S,
including the processing of received CAM, DENM, SPATEM, MAPEM and IVIM for the analysis of
intersection collision risks and provides warning to the driver in case of a detected risk. A driver warning
issued by an ICRW application is a strong advice that requires an immediate action from the driver to avoid an
imminent intersection collision.
• Road side ITS-S originating mode: This mode refers to functionalities implemented by a road side ITS-S,
including the triggering of DENM transmission upon detection of potential collision risk at intersection.
• Road side ITS -S receiving mode: This mode refers to functionalities implemented by a road side ITS-S,
including the processing of received CAM, DENM and/or sensor data for the detection of potential collision
risk at intersection.
A vehicle ITS-S implementing ICRW shall comply with one of the following compliance levels:
• Level 1: the minimum vehicle receiving mode functionality shall be implemented.
• Level 2: according to Level 1 and the full receiving mode functionality shall be implemented.
• Level 3: according to Level 2 and the vehicle ITS-S originating mode functionality shall be implemented.
A road side ITS-S implementing ICRW shall comply with both the road side ITS-S originating and receiving mode
functionalities.
The present clause describes ICRW functionalities of both modes.
ICRW may include use cases as defined in Basic Set of Applications (BSA) ETSI TR 102 638 [i.1], with their
functional requirements defined in ETSI TS 102 894-1 [i.3]. In summary, the following collision risks may be
considered as intersection collision risks:
• Crossing collision: the collision risk is detected between vehicles whose trajectories may cross in the conflict
zone. In most cases, the crossing collision results in a lateral collision. The vehicle may issue a warning to the
driver if it detects crossing collision. An immediate action e.g. emergency brake is required for the driver of
the vehicle to avoid the collision.
• Traffic sign violation: the traffic sign violation at an intersection area refers to either a traffic light violation at
a signalled intersection, or a priority violation at a non-signalled intersection (e.g. stop sign violation). The
conditions under which a violation is considered to be true may vary according to regional regulations.
Therefore, the violation risk detection algorithm of the ICRW should be compliant to such regulations.
• Collision involving Vulnerable Road Users (VRU): this collision risk refers to risk of collisions between
vehicles and Vulnerable Road Users e.g. bicycles, pedestrians inside the intersection area. A warning may be
issued to the vehicle driver if a collision risk is detected. If the VRU is equipped with ITS-S implementing the
ICRW e.g. a personal ITS-S, a warning may also be issued.
• Rear end collision: rear end collision may happen inside or near an intersection area, for example, at
intersection queues.
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10 ETSI TS 101 539-2 V1.1.1 (2018-06)
5.1.2 Crossing collision warning
The considered use cases related to crossing collision warning are summarized in Table 1 and described below.
Table 1: Relevant use cases description for crossing collision risk warning
Use case Scenario illustration
Turning collision risk warning

Merging collision risk warning

Collision risk warning for vehicles with missing
radio connectivity
Turning collision risk warning:
Detection by vehicle:
The collision risk is detected between vehicles, whose trajectories cross in the conflict zone of an intersection. In the
example scenario as presented in Table 1, a first vehicle is turning to the left and another vehicle is going straight across
the intersection. Both vehicle ITS-Ss receive SPATEM and MAPEM from road side ITS-S, allowing both of them
entering the intersection area. Both ITS-Ss transmit CAMs. The left turning vehicle is able to monitor continuously the
straight driving vehicle and calculates the associated Time Proximity Vector / Safety Shield (see annex A) with it. Once
the value is within a limit (the straight driving vehicle is within the safety shield), the left turning vehicle may increase
the CAM generation and transmission rate. Similar estimation may be done at straight driving vehicle, who in its turn
increases the CAM generation and transmission rate. Cooperatively, two vehicles are able to monitors more precisely
each other's kinematics status changes and detects the potential collision risk. If the collision risk probability reaches a
predefined threshold, a warning is issued to the driver.
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11 ETSI TS 101 539-2 V1.1.1 (2018-06)
In one other possible ICRW implementation, the vehicle detecting the potential crossing collision risk (e.g. using
embedded sensors) may trigger a DENM transmission. Other vehicle ITS-S receiving such DENM may evaluate the
collision risk with transmitting vehicle ITS-S and accordingly issue a warning to the driver.
NOTE: In regions where left hand traffic rules apply, the turning collision may be detected between right turn
vehicles with other vehicles.
Detection by roadside:
The roadside ITS monitors the straight driving and left turning trajectories of the two vehicle. Thus the roadside ITS is
able to estimate a potential collision risk in real time. Upon detection of collision risk the roadside ITS shall issue a
DENM to the traffic participants (e.g. vehicles, pedestrians, bicycles).
Merging collision risk warning:
Detection by vehicle:
The merging collision risk is detected between a vehicle with at least one other vehicle whose trajectory is merging with
the trajectory of the first vehicle. In the example scenario as presented in Table 1, the right turning vehicle is authorized
to make right turn with yellow phase, and the other vehicle is going straight across the intersection. Both vehicles
receive SPATEM and MAPEM from road side ITS-S, allowing the entrance to the intersection. The straight driving
vehicle is able to monitor (based on CAMs) constantly the turning vehicle and assess the collision risk probability. If
the collision risk probability reaches a predefined threshold, the vehicle issues a warning to the driver requesting
immediate action to avoid the collision.
Detection by roadside:
The roadside ITS monitors the straight driving and right turning trajectories of the two vehicles. Thus the roadside
ITS-S is able to analyse the potential collision risk in real time. Upon detection of collision risk the roadside ITS shall
issue a DENM to the traffic participants (e.g. vehicles, pedestrians, bicycles) within the intersection area.
Collision risk warning for vehicles with missing radio connectivity:
In this use case, an roadside ITS-S detects collision risk between at least two other vehicles inside the intersection area
and transmits a collision risk warning DENM. In the example scenario as presented in Table 1, a vehicle cannot receive
CAM from other vehicles because of non-line-of sight radio propagation due to obstacle. A road side ITS-S is
positioned at the intersection that has a line-of-sight condition with all road sections of the intersection. This road side
ITS-S receives CAMs from vehicles at both directions, enabling it to detect the collision risk of these two vehicles.
Optionally the roadside ITS-S uses additional technical means to detect the collision risk (e.g. radar, camera). Upon the
detection of a collision risk, the ICRW application of the roadside ITS-S triggers the transmission of "collision risk
warning" DENMs until the collision risk is eliminated. Upon reception of a DENM, a vehicle ITS-S may estimate the
relevance of the collision risk with its own trajectory and movement state, and triggers a warning to driving if
applicable.
5.1.3 Traffic sign violation warning
The considered use cases related to traffic sign violation are summarized in Table 2 and described below.
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12 ETSI TS 101 539-2 V1.1.1 (2018-06)
Table 2: Relevant use cases description for traffic sign violation warning
Use case Scenario illustration
Stop sign violation warning
Priority violation warning
Traffic light violation warning

Turning regulation warning
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13 ETSI TS 101 539-2 V1.1.1 (2018-06)
Stop sign violation warning:
In this use case, a stop sign violation risk is detected against a vehicle approaching to an intersection from a road
segment where a short stop is required before entering the intersection. In the example scenario as presented in Table 2,
a vehicle is approaching to the intersection from south. It receives an IVIM message from road side ITS-S and is
informed that a stop is required. The ICRW application (based on the vehicles speed) computes the distance required to
stop the vehicle and compares it with the remaining distance to the stop line. If a brake is required for the vehicle to stop
before the stop line or the violation cannot be avoided, a warning may be issued to the driver to brake or an action is
taken automatically by the in-vehicle system (e.g. automatic braking) in order to avoid the potential violation.
Optionally the ICRW of the roadside ITS, which tracks continuously the movement of the vehicle trajectories, will
compute a potential risk for stop sign violation and potential collisions.
The ICRW of the vehicle, which is about to violate the stop sign, or the roadside ITS may trigger a DENM warning. It
enables a receiving ITS-S to estimate the collision risk and accordingly triggers a warning to driver. In this case, this
use case is linked with the crossing or merging collision risk warning use cases as described in clause 5.1.2.
Priority sign violation warning:
In this use case, a priority violation risk is detected against a vehicle approaching to an intersection from the road
segment where it should give priority to traffic of other road segments before entering the intersection. In the example
scenario as presented in Table 2, the vehicle approaching from south, receives an IVIM message from the roadside ITS
and is informed that traffic on est-west road segment has higher priority. Additionally the vehicle receives CAMs from
the approaching vehicle from the east. The ICRW application may issue a warning to the driver, reminding him/her, that
a vehicle is approaching on the main road and that the priority should be given to the this vehicle, or an action is taken
automatically by the in-vehicle system (e.g. automatic braking).
Optionally the ICRW of the roadside ITS, which tracks continuously the movement of the vehicle trajectories, will
compute a potential risk for priority sign violation and potential collisions.
Additionally, the ICRW, of the vehicle which is about to violate the priority, or the roadside ITS may trigger a DENM
transmission. It enables a receiving ITS-S to estimate the collision risk and accordingly triggers a warning to driver. In
this case, this use case is linked with the crossing or merging collision risk warning use cases as described in
clause 5.1.2.
Traffic light violation warning:
In this use case, a traffic light violation risk is detected against a vehicle approaching to an intersection equipped with
traffic lights while the access is not allowed by the traffic light (e.g. traffic light is in red phase). In the example scenario
as presented in Table 2, a vehicle is approaching to the intersection from east and driving straight to exit the
intersection. It receives SPATEM/MAPEM message from road side ITS-S and is informed that the light is in red phase.
The ICRW application computes the distance and time required to stop the vehicle and compares it with the remaining
distance and time to the stop line and remaining red phase time. If a brake is required to stop the vehicle before the stop
line during the red phase, a warning may be issued to the driver or an action is taken automatically by the in-vehicle
system (e.g. automatic braking).
Optionally the ICRW of the roadside ITS-S, based on the knowledge of the of the intersection, the traffic light signage,
the allowed maneuvers and the trajectories of the vehicles, is able to estimate a red light violation and potential collision
risk in advance and to inform the violating vehicle.
Additionally, the ICRW, of the vehicle which is about to violate the traffic light, or the roadside ITS may trigger a
DENM transmission. It enables a receiving ITS-S to estimate the collision risk and accordingly triggers a warning to
driver. In this case, this use case is linked with the crossing or merging collision risk warning use cases as described in
clause 5.1.2.
Turning regulation violation warning:
In this use case, a turning regulation risk is detected against a vehicle exiting an intersection from segment that is not
allowed. In the example scenario as presented in Table 2, an vehicle is approaching from south, it receives an IVIM
message from roadside ITS-S and is informed that turning to left is not allowed at the intersection. The ICRW
application calculates the vehicle path prediction using in-vehicle data e.g. steering wheel angle, yaw rate, etc. and
estimates whether a turning violation risk exists. If yes, the ICRW application may issue a warning to the driver,
reminding him/her to take appropriate action to avoid the violation.
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14 ETSI TS 101 539-2 V1.1.1 (2018-06)
Optionally the ICRW of the roadside ITS, based on the knowledge of the of the intersection, the allowed maneuvers and
the trajectories of the vehicles, is able to estimate a turning violation. After detection of the risk the roadside ITS shall
inform the violating vehicle.
Additionally, the ICRW of the vehicle, which is about to violate the turning regulation, or the roadside ITS may trigger
a DENM transmission. It enables a receiving ITS-S to estimate the collision risk and accordingly triggers a warning to
driver. In this case, this use case is linked with the crossing or merging collision risk warning use cases as described in
clause 5.1.2.
5.2 ICRW originating mode functionalities
5.2.1 CAM transmission
Vehicle ITS-S or road side ITS-S implementing the ICRW application shall be able to transmit CAMs. The triggering
of CAM shall be as specified in ETSI EN 302 637-2 [1].
As additional feature, the CA basic service of a vehicle ITS-S may increase the CAM transmission rate when in the
safety field as described in annex A. It is recommended to include this feature in new release of the CA basic service.
NOTE: Decentralized Congestion Control mechanism may be needed to manage the network load.
5.2.2 DENM transmission: signalling of a traffic sign violation risk
When a collision risk or violation risk is detected, the ICRW application should trigger DENM transmission to inform
vehicle ITS-Ss approaching to or located in the intersection area.
The detection of traffic sign violation may be supported by the ICRW receiving mode functionalities, by processing
received messages from other vehicle ITS-Ss and from road side ITS-S. This functionality is described in clause 5.3.1.
Alternatively, the traffic light violation or priority violation may be detected by other means e.g. camera system with
image processing algorithm capable of detecting the traffic light violation, or with data from other sources e.g. digital
map.
5.2.3 DENM transmission: signalling of an intersection collision risk
When an intersection collision risk is detected, the ICRW application may trigger DENM transmission to inform
vehicle ITS-Ss approaching to or located in the intersection area.
The detection of intersection collision risk may be supported by the ICRW receiving mode functionalities, by
processing received messages from other vehicle ITS-S and from road side ITS-S. This functionality is described in
clause 5.3.1.
Alternatively, the collision risk may be detected by other means e.g. camera system with image processing algorithm
capable of detecting the vehicles' movement.
5.2.4 Interaction with other ITS-S layers
ICRW application may interact with functionalities of other ITS-S layers for:
• Optionally, adjusting the CAM time interval if necessary.
NOTE 1: Mechanisms for CAM rate control by application are defined in annex A of the ETSI TS 101 539-3 [3].
• Controlling DENM transmission.
• Inhibiting or enabling the ITS-S pseudonym change.
• Optionally, providing requirements to Decentralized Congestion Control (DCC).
• Informs lower layers of the priority level, if necessary.
ETSI
15 ETSI TS 101 539-2 V1.1.1 (2018-06)
NOTE 2: The priority level is assigned by ICRW receiving mode, according to the criticality of the traffic situation
perceived by the ITS-S. The priority level and traffic safety critical situation are defined in clause 5.3.1.
5.3 ICRW receiving mode functionalities
5.3.1 Detection of risk
5.3.1.1 Traffic sign violation risk detection
Detection by vehicle ITS-S: For the detection of a traffic light violation, the ICRW may use the SPATEM (Signal
Phase and Timing) and MAPEM messages. SPATEM and MAPEM shall be as specified in ETSI TS 103 301 [4].
A SPATEM message contains information of the current and/or future phase and timing information of traffic lights, a
MAPEM message contains information of the intersection topology (driving lanes, crosswalk lanes etc.) as well as
connectivity between lanes to enter and exit the intersection. By processing received SPATEM and MAPEM messages
of an intersection, a vehicle ITS-S is able to match the traffic phase and timing information with the position, speed of
the vehicle in order to estimate whether a traffic light violation risk exists.
For the detection of a priority violation, the ICRW application may use "Infrastructure to Vehicle Information" IVIM
message. IVIM shall be as specified in ETSI TS 103 301 [4]. An IVIM message contains information of a traffic
signage (including priority signage) as well as the area information in which the traffic sign is relevant. By processing
received IVIM of an intersection, a vehicle ITS-S is able to match the priority information with the position, speed of
the vehicle in order to estimate whether a priority violation risk exists.
Optionally, the vehicle ITS-S may trigger a DENM transmission as described in clause 5.2.2.
Detection by roadside ITS-S: The roadside ITS-S monitors the trajectories, speed and heading of the approaching
vehicles in the intersection and within the conflict area (e.g. based on received CAMs) in real time. Based on the
knowledge of the detailed map of the intersection (lane based), the traffic signage, the allowed maneuvers, the current
signal state of the traffic lights (for signalized intersections), and the trajectories of the vehicles the roadside ITS-S is
able to estimate a potential traffic rules violation and collision risk in advance. The roadside ITS-S triggers a warning
DENM right after first detection of potential signal violation to all traffic participants in the intersection.
Using additional sensor at roadside (e.g. radar, motion detectors, "angle of signal arrival a roadside", WEB-Cam) a
fusion of different information sources is possible. This enables the roadside ITS-S to enhance the prediction of traffic
participants breaking traffic rules and the estimation of potential risks.
5.3.1.2 Intersection collision risk detection
Detection by vehicle ITS-S: A vehicle ITS-S receives CAM/DENM from vehicles and SPATEM/MAPEM/IVIM from
road side ITS-Ss within the intersection area. It processes the received messages and estimates if paths of any vehicles
are crossing its own path. In addition, the vehicle ITS-S estimates if any collision risk exists for the crossing. If yes, the
ICRW of the vehicle issues an warning to the driver. Optionally the vehicle ITS-S may trigger a DENM transmission to
inform such collision risk to other vehicles, as described in clause 5.2.3.
Detection by roadside ITS-S: A roadside ITS monitors continuously the trajectories, speed and heading of the
approaching vehicles in the intersection and especially within the conflict area (e.g. based on received CAMs) in real
time. The roadside ITS has knowledge of the detailed map (lane topology) of the intersection, the traffic signage, the
allowed maneuvers, the current signal state of the traffic lights (for signalized intersections), and the trajectories of the
vehicles. Thus the ICRW application of the roadside ITS-S is able to estimate a potential violation of traffic r
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