ISO 20901:2020

INTERNATIONAL ISO
STANDARD 20901
First edition
2020-04
Intelligent transport systems —
Emergency electronic brake light
systems (EEBL) — Performance
requirements and test procedures
Systèmes de transport intelligents — Systèmes de diffusion de
l’information d'un freinage d'urgence (EEBL) — Exigences de
performance et procédures d'essai
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Specifications and requirements. 3
5.1 Basic functions . 3
5.2 Necessary functions . 4
5.3 Basic operation principle . 4
5.3.1 State functional descriptions. 5
5.3.2 Operational limits . 6
5.4 Alert functionality . 6
5.4.1 General. 6
5.4.2 Generating the message including emergency braking flag for broadcasting . 6
5.4.3 Judging to issue the alert . 6
5.5 Alerting element requirements . 7
5.5.1 EEBL-R output . 7
5.5.2 Alert modality. 7
5.5.3 Optional functions of EEBL-R . 7
5.6 Performance requirement of EEBL . 8
5.6.1 Minimum communication range . 8
5.6.2 System delay requirement between FV and SV . 8
5.7 Driver interface requirements . 8
5.7.1 Alert output specification. 8
5.7.2 Fault indication . 8
6 Performance evaluation test methods . 8
6.1 Environmental conditions for test . 8
6.2 Test course conditions . 9
6.3 Test system installation and configuration . 9
6.4 Parameters recoverable from data record . 9
6.5 Test cases . 9
6.6 Test procedure .10
6.6.1 Test case 1 — FV transmission test and delay measurement .10
6.6.2 Test case 2 — False positive test .12
6.6.3 Test case 3 — True positive test .13
6.6.4 Test case 4 — Test when there is interfering vehicle (IV) .14
6.6.5 Test case 5 — Basic communication function test .16
Bibliography .18
Foreword
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electrotechnical standardization.
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This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
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iv © ISO 2020 – All rights reserved

Introduction
Emergency Electronic Brake Light systems (EEBL) alert the driver against the danger caused by the
emergency braking of a forward vehicle (FV) on the upcoming road. EEBL generates an emergency
brake message based on vehicle emergency brake and transmit. The system periodically broadcasts
the message to nearby vehicles through vehicle to vehicle (V2V) wireless communication. If the
system equipped on an FV detects the emergency braking of its own vehicle, the system generates the
emergency braking flag, and sends the message including emergency braking flag. When the system
equipped on the subject vehicle (SV) receives the message containing the emergency braking flag,
the system judges whether an alert needs to be issued. If the location of the FV is within the specified
region of interest (ROI) of the SV, the system provides an alert to the driver to prompt appropriate
deceleration for driver safety. The scope of EEBL does not include automated intervention features or
means for controlling the vehicle to match a desired speed.
A significant benefit of cooperative safety systems such as EEBL is the significant reduction of the
potential risk of collision when a driver cannot see the brake light of an FV that is braking hard. For
example, when there is an interfering vehicle between the emergency braking vehicle (FV) and the SV,
the driver in the SV can still be alerted through vehicle to vehicle (V2V) wireless communication while
on-board sensor-based systems cannot even detect the existence of the FV.
INTERNATIONAL STANDARD ISO 20901:2020(E)
Intelligent transport systems — Emergency electronic
brake light systems (EEBL) — Performance requirements
and test procedures
1 Scope
This document contains the basic alert strategy, minimum functionality requirements, basic driver
interface elements, minimum requirements for diagnostics and reaction to failure, and performance
test procedures for Emergency Electronic Brake Light systems (EEBL).
EEBL alerts the driver against danger caused by the emergency braking of an FV on the upcoming
road, so that the driver may reduce the speed. The system does not include the means to control the
vehicle to meet the desired speed. The responsibility for safe operation of the vehicle always remains
with the driver.
The scope of this document does not include performance requirements and test procedures of the
wireless communication device used for EEBL. The requirements of communication devices are defined
[6][7][8]
in other standards, e.g. the IEEE series listed in the Bibliography . The test procedure in this
document is designed for third party testing of the product while the test procedure can also be used
for other stakeholders such as manufacturers or consumer unions.
The document applies to light duty vehicles and heavy vehicles. These systems are not intended for off-
road use.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
Emergency Electronic Brake Light system
EEBL
system consisting of EEBL-T (3.1.1) and EEBL-R (3.1.2)
3.1.1
Emergency Electronic Brake Light – Transmitting system
EEBL-T
system capable of detecting the emergency braking of the vehicle where the system is equipped, and
capable of transmitting a message including emergency brake flag and other information, e.g. location,
speed, to nearby vehicles
3.1.2
Emergency Electronic Brake Light – Receiving system
EEBL-R
system capable of receiving a message including emergency brake flag from forward vehicles (FVs) (3.3),
and capable of alerting the driver of emergency braking of an FV on the same road and traveling in the
same direction as the SV (3.2)
3.2
subject vehicle
SV
receiving vehicle
vehicle equipped with the EEBL-R (3.1.2) system
Note 1 to entry: The subject vehicle is located behind and traveling in the same direction as the forward vehicle
(FV) (3.3).
3.3
forward vehicle
FV
transmitting vehicle
vehicle equipped with the EEBL-T (3.1.1) system
Note 1 to entry: The forward vehicle (FV) (3.3) is located ahead of the subject vehicle (SV) (3.2) within the region of
interest (ROI) (3.9) of the SV.
3.4
interfering vehicle
IV
vehicle which is located in between the subject vehicle (SV) (3.2) and forward vehicle (FV) (3.3) to
interfere with the line-of-sight between the SV and FV
Note 1 to entry: During the test, the IV does not generate a message including emergency brake flag nor issue an
emergency brake alert to the driver, so the IV will not influence the EEBL (3.1) operation of the FV (3.3) and SV.
3.5
subject vehicle speed
longitudinal component of the subject vehicle (SV) (3.2) velocity
3.6
visibility
distance at which the illuminance of a non-diffusive beam of white light with the colour temperature of
2700K is decreased to 5 % of its original light source illuminance
3.7
host lane
lane in which the subject vehicle (SV) (3.2) is located
3.8
adjacent lane
lane of travel sharing one lane boundary with the host lane and having the same direction of travel as
the host lane
3.9
region of interest
ROI
area in which a subject vehicle (SV) (3.2) receives the emergency brake flag from the forward vehicle
(FV) (3.3)
2 © ISO 2020 – All rights reserved

4 Symbols and abbreviated terms
a The deceleration of the FV
d
a Absolute value of the deceleration of the FV
d_Current
a Threshold amount of deceleration of the FV to judge the emergency braking
d_Threshold
EEBL Emergency Electronic Brake Light system
EEBL-T Emergency Electronic Brake Light -Transmitting system
EEBL-R Emergency Electronic Brake Light - Receiving system
FSRA Full Speed Range ACC
FV Forward Vehicle
FVCWS Forward Vehicle Collision Warning System
GNSS Global Navigation Satellite System
HMI Human Machine Interface
IV Interfering Vehicle
PER Packet Error Rate
ROI Region of Interest
RSE Road Side Equipment
SV Subject Vehicle
V A pre-set speed of vehicle for test
V2I Vehicle to Infrastructure communication
V2V Vehicle to Vehicle communication
V Maximum operational speed value
max
5 Specifications and requirements
5.1 Basic functions
The purpose of the EEBL is to provide alerts that will assist drivers in avoiding or reducing the severity
of rear end crashes caused by emergency braking of an FV.
EEBL has following functions.
— EEBL-T detects and judges the emergency braking of an FV, and broadcasts a message including
the emergency braking flag. For better understanding, the vehicle that broadcasts the emergency
braking flag is denoted as FV in this document.
— EEBL-R receives the message including the emergency braking flag, judges whether the alert shall
be issued, and provides the alert to the driver. For better understanding, the vehicle whose driver is
alerted is denoted as SV in this document.
— The EEBL requires both of these functions, EEBL-T and EEBL-R, on separate vehicles. The
implementations can be different for different manufacturers on their respective vehicles.
The alert should be issued as soon as the SV receives the emergency braking message flag from an FV
within its ROI and has evaluated it to be relevant. EEBL provides an alert only and does not perform
vehicle control to mitigate the crash.
EEBL may suppress or delay the alert when the SV is applying an automatic braking or alert(s)
commanded by another system in the vehicle, e.g. FVCWS or FSRA.
The basic components of EEBL can include radio communication transmitter/receiver and antenna,
GNSS receiver and antenna, processing device and HMI device. The processing device can be a separate
control unit or it can be combined with another control unit.
5.2 Necessary functions
Vehicles equipped with EEBL-T shall be equipped to fulfil the following functions:
— monitor vehicle deceleration, vehicle position, vehicle speed and vehicle heading direction;
— detect emergency braking in accordance with deceleration threshold value;
— broadcast the message including emergency braking flag to nearby vehicles.
Vehicles equipped with EEBL-R shall be equipped to fulfil the following functions:
— receive the message including emergency braking flag;
— judge the position and heading of the FV with respect to the SV;
— provide alerts to driver in accordance with the EEBL function and requirements.
5.3 Basic operation principle
Figure 1 — EEBL states and transitions
4 © ISO 2020 – All rights reserved

5.3.1 State functional descriptions
5.3.1.1 State transition conditions
Conditions for EEBL transitions from system Off state to system On state:
a) For EEBL vehicles equipped with on/off control, both the vehicle ignition and the on/off control are
on.
b) For EEBL vehicles not equipped with on/off control, the vehicle ignition is on.
c) The transition from EEBL Off to EEBL On may be performed by the driver or automatically.
d) The transition from EEBL Off to EEBL On shall only occur if no EEBL system failures have been
detected.
Conditions for EEBL transitions from system On state to system Off state:
a) For EEBL vehicles equipped with on/off control, either the vehicle ignition or the on/off control
are off.
b) For EEBL vehicles not equipped with on/off control, the vehicle ignition is off.
c) If the system is in on state, and a system failure occurs.
The system may be fitted with an on/off control that can be operated by the driver at all times.
EEBL shall as a minimum, provide the following operations and state transitions. The following
constitutes the fundamental behaviour of EEBL. The alert criteria are described in 5.4.
— The EEBL-T system of an FV generates the message including the emergency braking flag as long as
the vehicle braking exceeds the threshold value ( a ), and returns back to the stand-by
d_Threshold
state after the vehicle braking no longer exceeds the threshold value. The system broadcasts the
message including the emergency braking flag to nearby vehicles through V2V wireless
communication within 100 ms of detecting the emergency brake.
— When the EEBL-R system of an SV is in the stand-by state, the system monitors messages from
external wireless communication sources. If a message including the emergency braking flag is
received, the system judges the alert criteria to determine whether the alert should be issued. If
the system judges to alert, the system transitions to the alert state, and the EEBL-R starts alert(s)
immediately.
— When the EEBL-R system of an SV is in the alert state, the system provides alert(s) to the driver for
a minimum 2 s, and maximum of the duration that the FV emergency braking flag is received, and
then returns back to the stand-by state.
One of several stages or phases of system operation.
— EEBL off state: The state that EEBL is off. This state has one of the following three causes: the driver
has selected the off condition, the ignition is off, or the EEBL is in failure. The failure of EEBL means
that the system cannot function as it is described in the user manual due to the failure of the system
or the failure of the sub-component of the EEBL. The cause of failure can be, e.g. system malfunction,
communication fail, failure during self- diagnosis process.
— EEBL system on state: For EEBL-T equipped on a FV, this state is either stand-by or broadcast state.
For EEBL-R equipped on an SV, this state is either stand-by or alert state. Vehicles equipped with
EEBL-T periodically broadcast and the vehicles equipped with the EEBL-R receive status messages.
— EEBL system stand-by state: For EEBL-T equipped on a FV, the system monitors the vehicle
deceleration. For EEBL-R equipped on an SV, the system is ready to receive the message including
the emergency braking flag.
— EEBL-T transmission of emergency braking state: The system generates the emergency braking
flag, and sends the message including emergency braking flag to nearby vehicles using wireless
communication module. The EEBL-T starts broadcasting the message including emergency braking
flag if the amount of deceleration of the vehicle exceeds the threshold value.
— EEBL-R alert state: The system starts alert(s) or is operating the alert(s). The EEBL-R starts alert(s)
if the message including emergency brake flag is received, and the system judged that the alert
criteria are all met.
5.3.2 Operational limits
The maximum operational speed value (for SV) of Vmax shall be greater than or equal to 27,8 m/s.
The s
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