ETSI TS 101 539-3 V1.1.1 (2013-11)

Intelligent Transport Systems (ITS); V2X Applications; Part 3: Longitudinal Collision Risk Warning (LCRW) application requirements specification

DTS/ITS-0010016

General Information

• Status: Published
• Publication Date: 04-Nov-2013
• Technical Committee: ITS WG1 - Application Requirements and Services
• Current Stage: 12 - Completion
• Due Date: 26-Nov-2013
• Completion Date: 05-Nov-2013

Standards Content (Sample)

Technical Specification
Intelligent Transport Systems (ITS);
V2X Applications;
Part 3: Longitudinal Collision Risk Warning (LCRW)
application requirements specification

2 ETSI TS 101 539-3 V1.1.1 (2013-11)

Reference
DTS/ITS-0010016
Keywords
application, ITS, performance
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3 ETSI TS 101 539-3 V1.1.1 (2013-11)
Contents
Foreword . 4
Introduction . 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 Longitudinal Collision Risk Warning application description . 10
5.1 LCRW in the ITS architecture . 10
5.1.1 Forward and forward / side collision risk warning . 11
5.1.2 Frontal collision risk warning . 12
5.2 LCRW originating mode functionalities . 13
5.2.1 CAM & DENM transmission . 13
5.2.2 Interaction with other ITS-S layers . 14
5.2.3 Longitudinal collision risk from a third party . 14
5.3 LCRW receiving mode functionalities . 14
5.3.1 Traffic safety critical situation evaluation . 14
5.3.2 Issuing warning to vehicle driver . 15
6 Application functional requirements . 15
6.1 Longitudinal collision risk detection requirements . 15
6.2 Warning triggering requirements . 16
6.3 Third party ITS-S warning functional requirements . 16
7 Application operational requirements . 16
7.1 Security and reliability requirements . 17
7.2 System minimum performance requirements . 17
7.2.1 Longitudinal alignment and vehicle position accuracy . 17
7.2.2 Communication coverage . 18
7.2.3 System end to end latency time . 18
7.2.4 Message processing performance . 18
7.2.5 Congestion control for G5A. 19
7.3 Third party ITS Station system performances requirements . 19
Annex A (informative): CAMs interval adjustment based on critical safety situation . 20
Annex B (informative): LCRW application state machine. 21
Annex C (informative): Minimum time for warning issuing . 23
Annex D (informative): Safety shield concept . 24
Annex E (informative): Warning presentation recommendations . 25
Annex F (informative): LCRW application interfaces . 26
Annex G (informative): G5 based exchange profile for LCRW . 27
Annex H (informative): Bibliography . 28
History . 29

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Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Intelligent Transport Systems
(ITS).
The present document is part 3 of a multi-part deliverable. Full details of the entire series can be found in part 1 [3].
Introduction
ITS Stations (ITS-Ss) are interacting together to satisfy a large diversity of customers' services.
ETSI TC ITS WG1 has defined a basic set of applications (BSA) [i.1] with the purpose to scope the WG1 work. Driven
by European safety and traffic management ITS directive, and within the scope of the European Mandate M/453 a
subset of the BSA application requirements specifications, dedicated to road safety, are developed by ETSI TC ITS.
The present document provides specifications on the application requirements related to Longitudinal Collision Risk
Warning (LCRW) application based on Co-operative Awareness basic service (CA basic service) [1] and Decentralized
Environmental Notification basic service (DEN basic service) [2].
A communication technology may be used to realize this application, as long as the functional and operational
requirements are satisfied. An ITS-S conforming to these functional and operational requirements are named
conforming ITS-S.
The LCRW application functionalities are distributed in conforming ITS-Ss, two functional modes of the application
are defined:
• The originating mode: including the triggering of DENM [2] transmission upon the detection of a longitudinal
collision risk and the transmission of CAM according to the CAM transmission rules as specified in [1].
Functional and operational requirements for this functional mode are defined in accordance with the RHS
application requirements specification [3].
• The receiving mode: referring to the analysis of longitudinal collision risks based on received information
from other ITS-Ss and provision of warning to driver in case of a detected risk. The driver warning is a strong
advice that requires an immediate action of the driver to avoid an imminent longitudinal collision.
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1 Scope
The present document provides a description of the Longitudinal Collision Risk Warning application requirements and
the specification of the necessary parameters and conditions to operate the application using CAM [1] and DENM [2]. It
includes the specifications of functional requirements and operational requirements of the LCRW application.
2 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
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://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.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 302 637-2 (V1.3.0): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[2] ETSI EN 302 637-3 (V1.2.0): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Part 3: Specifications of Decentralized Environmental Notification
Basic Service".
[3] ETSI TS 101 539-1: "Intelligent Transport Systems (ITS); V2X Applications; Part 1: Road Hazard
Signalling (RHS) application requirements specification".
[4] ETSI TS 102 637-1 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Part 1: Functional Requirements".
2.2 Informative references
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] TISA specification TAWG11071 (2011-11-07, drafted to potentially become ISO/TS 21219
Part 15): "Intelligent Transport Systems (ITS) - Traffic and Travel Information (TTI) via Transport
Protocol Experts Group, Generation 2 (TPEG2) - Part 15: Traffic Event Compact
(TPEG2 TEC-3.1/001)".
[i.3] ISO 17425: "Data exchange specification for in-vehicle presentation of external road and traffic
related data ("embedded VMS").
[i.4] ETSI TS 101 539-2: "Intelligent Transport System (ITS); V2X Applications; Intersection Collision
Risk Warning (ICRW) application requirements specification".
[i.5] ETSI EN 302 665 (V1.1.1): "Intelligent Transport Systems (ITS); Communications Architecture".
[i.6] ISO/CD 15623: "Road Vehicles - Forward Vehicle Collision Warning System - Performance
requirements and tests procedures".
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[i.7] ETSI EN 302 895: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of
Applications; Local Dynamic Map (LDM)".
[i.8] ETSI TS 102 894-1: "Intelligent Transport Systems (ITS); Users and applications requirements;
Part 1: Facility layer structure, functional requirements and specifications".
[i.9] ETSI EN 302 636-4-1: "Intelligent Transport Systems (ITS); Vehicular Communications;
GeoNetworking; Part 4: Geographical addressing and forwarding for point-to-point and
point-to-multipoint communications; Sub-part 1: Media-Independent Functionality".
3 Definitions and abbreviations
3.1 Definitions
For the purpose of the present document, the following terms and definitions apply:
age of data: time elapsed since the time when a data is set at the originating ITS-S and a specific reference time
end to end latency time: age of data with a reference time at which the application processing result is effective
forward vehicle: vehicle in front of the ego vehicle along its itinerary
LCRW: application layer entity that implements at least one longitudinal collision risk warning use case
longitudinal alignment: two vehicles are considered as longitudinally aligned when their trajectories may lead to a
forward or frontal collision whatever surface portion of the vehicles being in contact at collision time
primary road safety application: application with objective of preventing a potential collision
NOTE 1: Multiple means are possible, ranging from giving information to the driver to acting directly on the
vehicle.
NOTE 2: Secondary and tertiary safety applications do not avoid collision. They respectively can mitigate the
collision (pre-crash and post crash) or accelerate the emergency rescue.
Subject Vehicle (SV): vehicle that estimates the collision risk and provides information or warning to driver when
necessary
Target Vehicle (TV): counterpart of the subject vehicle for the evaluation of collision risk
3.2 Abbreviations
For the purpose of the present document, the following abbreviations apply:
ABS Anti-lock Braking System
ADAS Advanced Driver Assistance System
BSA Basic Set of Applications
CA Co-operative Awareness
CAM Co-operative Awareness Message
CCH Control Channel
DCC Distributed Congestion Control
DEN Decentralized Environmental Notification
DENM Decentralized Environmental Notification Message
ESP Electronic Stability Program
FR Functional Requirement
GBC Geo Broadcasting
HMI Human Machine Interface
ICRW Intersection Collision Risk Warning
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ITS Intelligent Transport System
ITS-S ITS station
IVI In Vehicle Information
LCRW Longitudinal Collision Risk Warning
MAT Maximum Action Time
MDRT Maximum Driver Reaction Time
MLT Maximum end to end Latency Time
OEM Original Equipment Manufacturer
OR Operational Requirements
RHS Road Hazard Signalling
SHB Single Hop Broadcasting
SV Subject Vehicle
TPEG Transport Protocol Experts Group
TTC Time to Collision
TV Target Vehicle
4 Conforming ITS-S performance class definition
Primary road safety applications are ITS applications that target at reducing the risk of collision and thus improving the
road safety. Primary road safety applications may be realized with different technical means ranging from providing
information about road hazard to driver up to acting on vehicle systems to avoid a potential collision.
The performance of a primary road safety applications can be divided into three parts:
• The ITS-S originating part performance related to the transmission of Cooperative Awareness Messages
(CAM) [1] and Decentralized Environmental Notification Messages (DENM) [2].
• The wireless communication performance, which may vary according to network characteristics, radio
obstacles and network load.
• The ITS-S receiving part performance related to the processing of received information, presenting
information to driver or acting on the in vehicle system.
An overview of ITS applications according to their proximity to potential collision (time to collision) is illustrated in
Figure 1.
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NOTE: The position of an application relative to the TTC are illustrated as examples. Exact TTC numbers are out
of scope of the present document.

Figure 1: Overview of road safety applications
From user viewpoint, several services may be provided by the primary road safety application, in order to increase
driver awareness and collision avoidance capabilities of vehicle, for example:
• An "information" may be provided by telematics service (e.g. TPEG [i.2]) using e.g. digital radio broadcasted
channels or by cellular network.
• An "In-Vehicle Information" (IVI) may be provided by a road side ITS-S or a central ITS-S to provide static
road signage or variable message sign information [i.3].
• A "Awareness" information may be provided by Road Hazard Signalling application as specified in [3],based
on processing of received CAM [1] and DENM [2].
• A "warning" may be provided to driver by the Intersection Collision Risk Warning (ICRW) [i.4] and the
LCRW applications, based on processing of received CAM [1], DENM [2] and other messages.
• An automatic action is taken by in vehicle system in order to avoid the imminent collision risk. User may or
may not be warned.
The present document focuses on the LCRW applications.
One important quality parameter for receiving ITS-S to realize the primary road safety application is the age of data, in
particular the age of highly dynamic data. The receiving ITS-S may take erroneous decision if the received data does
not correspond to the latest situation of the originating ITS, e.g. trajectory, velocity of the target vehicle. Therefore, the
quality of the offered customer' service by the LCRW application rely on the quality and the availability of data
transmitted from the originating ITS-S.
The age of data estimated at the receiving ITS-S is denoted as end to end latency time as illustrated in Figure 2.
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Figure 2: Application end to end latency time
For collision risk warning applications as illustrated in Figure 1, 300 milliseconds end to end latency time may be
required to avoid false decision due to old data. This value corresponds to about 10 meters distance travelled by a
vehicle moving at 130 km/hour.
In Figure 2, the following time parameters are defined:
T0: Time at which the vehicle data is available at the vehicle electronic systems.
T1: Time stamp information included in CAM, DENM. For CAM, this time stamp corresponds to the time at
which the position information is updated, as specified in [1]. For DENM, the time stamp corresponds to the
time at which an event is detected, as specified in [2].
T2: Time at which the message is transmitted over the air by the originating ITS-S.
T3: Time at which the message is received at the access layer (antenna level) of the receiving ITS-S.
T4: Time at which the data of the received message is provided to the ITS facilities layer for processing.
T5: Time at which the application processing is finished. The application may request a driver action, if applicable.
T6: 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.
The end to end latency time is the time difference between T0 and T6. Even though the latency time T1 to T4 may be
calculated by comparing the time at which the message is received at facilities layer (T4) and time stamp information
included in CAM / DENM, the T0 - T1 latency time remains unknown for the receiving ITS-S.
Without knowledge on the T0 to T1 time the receiving ITS-S cannot predict vehicle trajectory and estimate the potential
collision risk with originating ITS-S.
NOTE 1: The T4 - T6 latency time depends on the implementation. The required value is out of the scope of the
present document.
For this purpose at least two ITS-S performance classes are defined for ITS-S originating part performance:
� Class A: a class A ITS-S shall guarantee a T0 to T1 less than 150 milliseconds.
� Class B: No requirement on T0 to T1.
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NOTE 2: T0 - T1 reflects the freshness of in-vehicle data with regards to the message time stamp. For a class A
system, the CAM generation intervals should be adjusted properly by the CA basic service to reflect the
latest value of the in vehicle data.
NOTE 3: Additional performance class may be added in the future.
The conformance class information shall be transmitted by ITS-S, as long as the information is available. It is included
in a data element in CAM as specified in [1], in order to enable the receiving ITS-S to estimate the age of received data
(worst case age: T4 - T1 + 150 ms).
5 Longitudinal Collision Risk Warning application
description
5.1 LCRW in the ITS architecture
Longitudinal collision refers to the collision between vehicles (or a vehicle and an obstacle) at any part on the front or
rear side of vehicle. If a longitudinal collision risk is detected, a subject vehicle (SV) may issue a collision risk warning
to driver. The counterpart vehicle or obstacle is called the target vehicle TV or target obstacle.
LCRW is an application layer entity that implements at least one longitudinal collision risk use case. In one possible
implementation, an LCRW may include more than one longitudinal collision risk use cases into one application entity.
The present document does not specify any implementation structure of the LCRW application.
Figure 3 presents the LCRW in the ITS-S architecture as defined in [i.5] as well as its logical interfaces with other
entities and layers.
Applications
LCRW
Originating mode Receiving mode
functionalities functionalities
FA-SAP
Facilities
Networking & Transport
Access
Figure 3: LCRW and logical interfaces
The LCRW application functionalities are distributed in conforming ITS-Ss, two functional modes of the application
are included:
• The originating mode: including the triggering of DENM [2] transmission upon the detection of a road hazard
or the detection of longitudinal collision risk, and the transmission of CAM according to the CAM
transmission rules as specified in [1]. Some functional requirements are provided in [4] for traffic situations
which may be leading to a longitudinal collision.
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• The receiving mode: including the processing of received CAM and DENM from TV for the analysis of
longitudinal collision risks and provides warning to the driver in case of a detected risk. A driver warning
issued by an LCRW application is a strong advice that requires an immediate action of the driver to avoid an
imminent longitudinal collision.
An ITS-S implementing LCRW shall implement both originating mode functionalities and receiving mode
functionalities. Interactions may be required between these two modes.
The present clause describes LCRW functionalities of both modes.
LCRW may include use cases as defined in Basic Set of Applications (BSA) [i.1], with their functional requirements
defined in [4]. In summary, the following collision risks may be considered as the longitudinal collision risks:
• Forward collision: the SV detects the risk of a collision with a forward vehicle or an obstacle e.g. roadwork
zone, in its trajectory. An immediate action e.g. emergency brake is required for the driver of the SV to avoid
the collision.
• Forward / side collision: a vehicle wants to overtake a vehicle while a third vehicle has already started the
overtaking manoeuvre and is approaching to the overtaking vehicle. The two overtaking vehicles detect a
collision risk which each other. This scenario corresponds to a typical accident scenario for motorcycles
approaching at high speed to a vehicle which intend to overtake another vehicle. In this case, both the
overtaking vehicle and the approaching vehicle are considered as SVs as each one may initiate a warning to
the driver requiring an immediate action to avoid the collision. In meanwhile, both vehicles are also considered
as target vehicle to each other, since movement status and trajectory of each vehicle is analyzed by other
vehicle in order to estimate the collision risk.
• Frontal collision: at least two SVs moving in opposite direction detect the risk of collision between
themselves. Also in this scenario both vehicles may be considered as SV and TV. This may happen when one
of the two vehicles is driving in a wrong direction on a one way road. A warning may be issued to both
vehicles' drivers.
5.1.1 Forward and forward / side collision risk warning
The considered use cases related to forward and forward / side collision risk warning are summarized in Table 1.
Table 1: Relevant use cases description for forward and forward / side collision risk warning

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12 ETSI TS 101 539-3 V1.1.1 (2013-11)
Safety relevant lane change: in this use case, SV are two vehicles being involved, i.e. the first vehicle that signals its
lane change and a second vehicle that is driving at high speed on the lane that the first is changing to. One possible
example of the use case is the overtaking scenario, when the first vehicle starts an overtaking manoeuvre while a second
vehicle is already driving in the overtaking lane.
If the first SV is effectively changing the lane, then the two considered vehicles would be aligned so creating a risk of
longitudinal collision. In this situation the first vehicle should refrain to do it and stay in its lane (keep lane). The second
vehicle should slow down. The LCRW application is to warn both involved vehicles' drivers to attempt avoiding the
collision.
Emergency electronic brake light / Traffic condition: in this use case, the SV is heading in the direction of a TV
which is abruptly slowing down (e.g. due to a traffic jam condition). The objective of the LCRW application is to warn
the SV's driver, in due time, in order for him to adapt its speed to avoid a collision with the TV.
Roadworks: in this use case, the SV is driving at a speed that is not adapted to the road work situation ahead. The
objective of the LCRW application is to warn the SV driver, in due time, in order for him to adapt its speed to avoid
losing the control of vehicle or hitting workers / obstacles when entering the road work area.
Stationary vehicle: in this use case, the SV is heading in the direction of an immobilized TV (such as breakdown,
accident etc.). The objective of the LCRW application is to warn the SV driver, in due time, in order for him to adapt its
speed to avoid a collision with the immobilized TV.
Stability problem: in this use case a TV entering a slippery road area may partially or completely lose the traction. The
objective of the LCRW application is to warn SVs approaching to the slippery road area based on the received CAM /
DENM transmitted from the TV e.g. by analysing the yaw rate, Electronic Stability Program (ESP) status and/or Anti-
lock Braking System (ABS) status of TV.
Collision risk warning from a third party: in this use case, the SV cannot perceive a risk of forward collision with the
TV ahead due to radio obstacle. A third party ITS-S e.g. a road side ITS-S, a central ITS-S or another vehicle ITS-S,
perceiving the risk of collision between the two vehicles may transmit "collision risk" DENMs as defined in [2]. Upon
reception of such DENM, a SV driver should adjust the behaviour to avoid a forward collision. The road topologies that
may benefit from this use case are for example:
• A curved road with radio obstacles, e.g. trees, building preventing direct communication between the SV and
the TV.
• A road with altitude variations (slope) creating radio obstacle for direct V2V communications) between the SV
and the TV.
• Intersections with a high accident risk. Specific detection means equipped at the intersection e.g. camera
systems may detect collision risk between vehicles or between vehicles and obstacles e.g. pedestrians, then a
road side ITS-S may transmit "collision risk" DENM.
5.1.2 Frontal collision risk warning
The considered use cases related to frontal collision risk warning are summarized in Table 2.
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Table 2: Relevant use cases description for frontal collision risk

Wrong way vehicle driving: in this use case the SVs are the countersense vehicle and vehicle driving in the normal
direction. The objective of the LCRW application is to warn SVs' drivers, in due time, for them to slow down or even to
stop their vehicles in order to avoid a frontal collision.
NOTE 1: Use case scenario should be compliant to legal requirements of the implementation environment.
NOTE 2: The SV may be only the countersense vehicle, or the oncoming vehicles.
Safety relevant vehicle overtaking warning: in this use case the SV is signalling its intent to overtake a slow vehicle
and
...