ISO 15623:2013

Intelligent transport systems - Forward vehicle collision warning systems - Performance requirements and test procedures

ISO 15623:2013 specifies performance requirements and test procedures for systems capable of warning the driver of a potential rear-end collision with other vehicles ahead of the subject vehicle while it is operating at ordinary speed. The FVCWS operate in specified subject vehicle speed range, road curvature range and target vehicle types. ISO 15623:2013 covers operations on roads with curve radii over 125 m, and motor vehicle including cars, trucks, buses, and motorcycles. Responsibility for the safe operation of the vehicle remains with the driver.

Systèmes intelligents de transport — Systèmes d'avertissement de collision frontale du véhicule — Exigences de performance et modes opératoires

General Information

• Status: Published
• Publication Date: 22-Jul-2013
• ICS: 03.220.01 - Transport in general
• ICS: 35.240.60 - IT applications in transport
• ICS: 43.040.99 - Other road vehicle systems
• Technical Committee: ISO/TC 204 - Intelligent transport systems
• Drafting Committee: ISO/TC 204/WG 14 - Vehicle/roadway warning and control systems
• Current Stage: 9060 - Close of review
• Completion Date: 04-Mar-2030

Relations

• Revises: ISO 15623:2002 - Transport information and control systems - Forward vehicle collision warning systems - Performance requirements and test procedures
• Effective Date: 15-May-2010

Overview

ISO 15623:2013, "Intelligent transport systems - Forward vehicle collision warning systems - Performance requirements and test procedures," defines baseline performance requirements and test methods for forward vehicle collision warning systems (FVCWS). The standard applies to systems that warn drivers of potential rear‑end collisions with vehicles ahead while the subject vehicle is operating at ordinary speeds. Coverage includes operation on roads with curve radii greater than 125 m and target vehicle types such as cars, trucks, buses, and motorcycles. The document clarifies that responsibility for safe vehicle operation remains with the driver.

Key Topics and Technical Requirements

• System functionality and classification - Defines FVCWS purpose (provide timely driver warnings to avoid or mitigate rear‑end crashes) and system classes based on capability and operating envelopes.
• Detection and sensing requirements - Requirements to detect forward vehicles, measure relative position/velocity, and estimate subject‑vehicle path. Terms such as TTC (time to collision), ETTC (enhanced TTC), RCS (radar cross section) and RCTT (reflection coefficient of test target) are specified for consistent testing and evaluation.
• Operating envelope - Specifies subject vehicle speed ranges, maximum curve lateral acceleration, and curve radii (>125 m) within which performance is assessed.
• Warning logic and human interface - Defines warning modalities (visual, auditory, haptic), warning timing (preliminary and collision warnings), and user safety/human‑machine interface requirements to avoid nuisance alerts while ensuring timely alerts.
• Test procedures and evaluation methods - Includes test target specifications, environmental conditions, and concrete test methods for:
  • Detection zone assessment
  • Warning distance range and accuracy
  • Target discrimination ability
  • Performance on curves
• Limitations and safety - Requires awareness of system limitations and guidance for interactions with other vehicle systems (e.g., adaptive cruise control).

Practical Applications and Who Uses It

ISO 15623:2013 is intended for:

• Automotive OEMs and Tier‑1 suppliers designing or integrating FVCWS into vehicles.
• Test laboratories and certification bodies that validate detection performance, warning accuracy and system behavior under defined test conditions.
• Regulators and road safety agencies referencing objective performance and test methods for policy or compliance frameworks.
• Standards developers and researchers working on ITS, collision avoidance, and advanced driver assistance features.

Use cases include component specification, system validation, type approval testing, and baseline interoperability among forward‑collision technologies.

Related Standards

• ISO 15622 - Adaptive Cruise Control (referenced for ACC interactions)
• IEC 825‑1 - Safety of laser products (normative reference for laser/radar test targets)

ISO 15623:2013 provides a practical, testable foundation for reliable forward collision warning system design and evaluation within the intelligent transport systems (ITS) ecosystem.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 15623
Second edition
2013-07-15
Intelligent transport systems —
Forward vehicle collision warning
systems — Performance requirements
and test procedures
Systèmes intelligents de transport — Systèmes d’avertissement
de collision frontale du véhicule — Exigences de performance et
modes opératoires
Reference number
©
ISO 2013
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – 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 . 4
5 Specifications and requirements. 5
5.1 System functionality . 5
5.2 Necessary functions . 5
5.3 Operating model . 5
5.4 Warning functionality . 6
5.5 Warning elements requirements . 7
5.6 System Classification . 9
5.7 Obstacle vehicle detection area and performance .10
5.8 FVCWS performance on curves .11
5.9 User safety requirements .12
5.10 Human interface requirements .12
5.11 Awareness of system limitations .13
6 Evaluation test method for measuring detection performance .13
6.1 Test target specification .13
6.2 Environmental conditions .13
6.3 Test method for detection zone .13
6.4 Test method for warning distance range and accuracy .14
6.5 Test method for target discrimination ability .15
Annex A (informative) Basic consideration of collision warning .18
Annex B (informative) Obstacle detection along curves .23
Annex C (informative) Laser radar — Coefficient of test target .25
Annex D (informative) Radio wave radar test target geometry .29
Bibliography .30
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
The committee responsible for this document is ISO/TC 204, Intelligent transport systems.
This second edition cancels and replaces the first edition (15623:2002), which has been technically revised.
iv © ISO 2013 – All rights reserved

Introduction
The main system function of a forward vehicle collision warning system (FVCWS) is to warn the driver
when the subject vehicle encounters the situation of a forward vehicle in the subject vehicle’s trajectory
becoming a potential hazard. This is done by using information such as: (1) the range to forward vehicles,
(2) the relative velocity of the forward vehicles with respect to subject vehicle and (3) whether a forward
vehicle is in the subject vehicle trajectory. Based upon the information acquired, the controller identified
as “FVCWS target selection and warning strategy” in Figure 1 produces the warning to the driver.
Figure 1 — Functional forward vehicle collision warning system’s elements
Automobile manufacturers and component suppliers throughout the world have been vigorously
pursuing the development and commercialisation of these FVCWS systems. Systems of this type have
already been introduced on to the market in some countries. Thus the standardization efforts began
in 1994 amongst interested countries. This International Standard is composed to address only the
basic performance requirements and test procedures for the FVCWS type systems. This International
Standard may be used as a basis by other standards for systems which have more features and may
extend beyond this International Standard.
INTERNATIONAL STANDARD ISO 15623:2013(E)
Intelligent transport systems — Forward vehicle
collision warning systems — Performance requirements
and test procedures
1 Scope
This International Standard specifies performance requirements and test procedures for systems
capable of warning the driver of a potential rear-end collision with other vehicles ahead of the subject
vehicle while it is operating at ordinary speed. The FVCWS operate in specified subject vehicle speed
range, road curvature range and target vehicle types. This International Standard covers operations
on roads with curve radii over 125 m, and motor vehicle including cars, trucks, buses, and motorcycles.
Responsibility for the safe operation of the vehicle remains with the driver.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
IEC 825-1:1993, Safety of laser products — Part 1: Equipment classification, requirements and user’s guide
(includes update of 1994)
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
collision warning
information that the system gives to the driver indicating the need for urgent action to avoid or reduce
the severity of a potential rear end collision with another forward vehicle
Note 1 to entry: This warning is issued in the advanced stages of a dangerous situation to warn the driver of the
need to perform emergency braking, lane changing or other emergency manoeuvres in order to avoid a collision.
3.2
reflection coefficient of test target
RCTT
optical radar reflectivity of the target, which is defined as the radiated intensity towards the receiver (Iref
- W/sr) measured at target level, immediately after the reflection; divided by the intensity of irradiation
received from the transmitter (Et - W/m ) measured at target level, immediately before the reflection
Note 1 to entry: The units for RCTT value are in m /sr (see Annex C).
3.3
forward vehicle
vehicle in front of and moving in the same direction and travelling on the same roadway as the subject vehicle
3.4
forward vehicle collision warning system
FVCWS
system capable of warning the driver of a potential collision with another forward vehicle in the forward
path of the subject vehicle
3.5
obstacle vehicles
vehicles, both moving and stationary, considered potential hazards that can be detected by this system
EXAMPLE Motor vehicles only, that is cars, trucks, buses, and motorcycles.
3.6
preliminary collision warning
information that the system gives to the driver in the early stages of a potentially dangerous situation
that may result in a rear end collision.
Note 1 to entry: The system may provide this warning prior to the collision warning.
3.7
radar cross section
RCS
measure of the reflective strength of a radar target measured in square meters, and defined as 4π times
the ratio of the power per unit solid angle scattered in a specified direction to the power per unit area in
a radio wave incident on the scatterer from a specified direction
3.8
visibility
distance which the illuminance of a non-diffusive beam of white light with the colour temperature of
2700 K is decreased to 5 % of its original light source illuminance
3.9
adaptive Cruise Control
ACC
enhancement to conventional cruise control systems which allows the subject vehicle to follow a forward
vehicle at an appropriate distance by controlling the engine and/or power train and optionally the brake
Note 1 to entry: See ISO 15622.
3.10
adjacent lane
lane of travel sharing one lane boundary with the lane in which the subject vehicle is traveling and
having the same direction of travel as the subject vehicle lane
3.11
clearance
x (t)
c
distance x (t) from the target vehicle trailing surface to the subject vehicle leading surface
c
x (t)
c
3.12
cut-in vehicle
forward adjacent vehicle that has a lateral component of motion towards the path of the subject vehicle
3.13
jerk
third derivative with respect to time of the position of an object; equivalently the rate of change of the
acceleration of an object; considered a measure of harshness of vehicle motion
3.14
minimum velocity
V )
min
minimum subject vehicle (SV) speed for which the FVCWS must be capable of initiating a warning
2 © ISO 2013 – All rights reserved

3.15
rear-end collision
forward vehicle collision in which the front of the subject vehicle strikes the rear of the forward vehicle
3.16
relative velocity
v (t)
r
difference between the longitudinal velocities of the subject vehicle (SV) and the target vehicle (TV),
v (t), given by the equation; equivalently the rate of change with respect to time of the distance between
r
the two vehicles. A positive value of relative velocity indicates that the target vehicle is moving faster
than the subject vehicle, and that the distance between them is increasing with time
vt()=−vt() vt()
rTVSV
3.17
required deceleration
A
req
minimum deceleration that, if constant, would enable the subject vehicle to match the velocity of the
target vehicle without contacting the target vehicle and thus prevent a collision:
((Vt))
r
At()=+A
reqTV
2*(xt()−xt())
cr
Note 1 to entry: x (t) is the amount of reduction in the clearance distance due to reaction time.
r
3.18
subject vehicle
SV
vehicle equipped with FVCWS as defined herein
3.19
target vehicle
TV
forward vehicle that is closest in the forward path of the subject vehicle; forward vehicle that the
FVCWS operates on
3.20
time to collision
TTC
estimated time that it will take a subject vehicle to collide with the target vehicle assuming the current
relative speed remains constant, as given in the following equation:
xt()
c
TTC=−
vt()
r
3.21
enhanced time to collision
ETTC
time that it will take a subject vehicle to collide with the target vehicle assuming the relative acceleration
between the subject vehicle (SV) and target vehicle (TV) remains constant, as given in the following equation:
 2 
−−()vv −−()vv −−2*(aa )*x
TV SV TV SV TV SV c
 
 
ETTC =
()aa−
TV SV
3.22
warning braking
action in which FVCWS respond to detection of a possible rear-end collision by automatically applying
the brake for a short period of time to provide a warning to the driver
3.23
FVCWS warning modalities
means used to convey the different type of FVCWS warnings to the driver.
EXAMPLE Visual, auditory, and/or haptic cues.
3.24
lateral offset
lateral distance between the longitudinal centerlines of a subject vehicle (SV) and a target vehicle (TV),
measured as a percentage of the width of the SV, such that if the centers of the two vehicles are aligned,
the value is zero
TV
SV
4 Symbols and abbreviated terms
a maximum allowed lateral acceleration in curves
lateral_max
a minimum deceleration of the subject vehicle’s emergency braking
min
d minimum detectable distance without distance measuring capability
d minimum detectable distance with distance measuring capability
d minimum detection distance for a cut-in vehicle
d maximum detectable distance
max
h upper detection height from ground
h lower detection height from ground
RCTT reflection coefficient for test target for infrared reflector
T maximum driver’s brake reaction time after the warning
max
T minimum driver’s brake reaction time after the warning
min
Tresp driver brake reaction time
Tb braking system response time
RCS radar cross section
V speed of the test vehicles at the start of the test
circle_start
V maximum vehicle speed at which the system is capable of operating
max
V minimum vehicle speed at which the system is capable of operating
min
V maximum relative vehicle speed at which the system is capable of operating
rel_max
W lane width
L
W subject vehicle width
V
4 © ISO 2013 – All rights reserved

5 Specifications and requirements
5.1 System functionality
The purpose of the FVCWS is to provide warnings that will assist drivers in avoiding or reducing the
severity of rear end crashes. These warnings should be provided in time to help drivers avoid most
common rear end crashes by applying the brakes only. The timing of the alerts should be selected such
that they strive to provide alerts early enough to help the driver avoid the crash or mitigate the harm
caused by the crash without introducing other alerts perceived as nuisance or false. FVCWS provide
warning only and do not perform vehicle control to mitigate the crash.
FVCWS may operate differently when the subject vehicle is applying an automatic braking commanded
by other system in the vehicle such as full speed range ACC. In this situation, the FVCWS could take into
account the capability of the automatic braking system. The fact that the vehicle is under sustained
automatic braking may affect the warning criteria and warning modality.
5.2 Necessary functions
Vehicles equipped with FVCWS shall be equipped to fulfil the following functions.
— Detect the presence of forward vehicles,
— Determine measure or measures for relative position and position dynamic of the detected forward
vehicles with respect to the subject vehicle,
— Determine the subject vehicle velocity,
— Estimate the path of the subject vehicle (Class II and III),
— Provide driver warnings in accordance with the FVCWS function and requirements.
5.3 Operating model
Figure 2 shows the state transition diagram for the FVCWS.
[1–2]
Off (1) StandBy (2)
[2–1]
[3–1] [3–2] [2–3]
Active (3)
Figure 2 — FVCWS State Transition Diagram
Key
[1-2] engine running, or engine running and on switch (if on switch exists)
[2-1] ignition off or off switch or fault condition
[3-1] ignition off or off switch or fault condition
[2-3] V < = speed < = V and gear is not in reverse or park positions
min max
[3-2] (V > speed) or (speed > V ) or gear is in reverse or park positions
min max
5.3.1 State functional descriptions
The FVCWS state descriptions address the functional contents of FVCWS, identifying what functions
are performed in each state. Descriptions that correspond to a functional requirement are presented
in bold text.
5.3.1.1 FVCWS off (1)
No warning is performed in the FVCWS off state. It is optional to provide a driver-selected means of
placing FVCWS in this state, other than the Ignition key (for example: on/off Switch). Upon turning
the ignition to the off position, the FVCWS transitions to the FVCWS off state. Whenever the Self-
Test function determines that the FVCWS is not able to deliver adequate performance, a fault
condition is set and FVCWS transitions to the FVCWS off state.
5.3.1.2 FVCWS standby (2)
No warning is performed in the FVCWS standby state. In this state, FVCWS monitors the vehicle speed
and the gear position. If the vehicle speed comes within the FVCWS operating range and the gear
select is in forward position (all gear positions except reverse and park), the system transitions
from the standby state to the active state. FVCWS enters the FVCWS standby state from the FVCWS
off state if the ignition cycle has been completed and the engine is running, or if the engine is
running and the optional on/off switch is the “on” position. FVCWS enters this state from the
active state if the conditions for activating are not met: if the vehicle speed value is outside the
FVCWS operation range (hysteresis delta is added), reverse gear is selected, or park is selected.
5.3.1.3 FVCWS active (3)
The warning is performed in this state whenever the warning conditions are met. FVCWS enters
this state if gear select is in any forward position and the vehicle speed value is in the FVCWS
operation range.
5.3.2 Operational limits
The value of V shall be at most 11,2 m/s. The value of V shall be at least the minimum of 27,8 m/s
min max
and the maximum vehicle operating speed. The value for V shall be at most 4,2 m/s. The value of
rel_min
V shall be at least 20 m/s.
rel_max
5.4 Warning functionality
Forward vehicle collision warning systems shall provide warnings for moving (including “has been
detected as moving by the sensor and now stopped”) obstacle vehicles. Providing warnings for stationary
obstacle vehicles (has never been detected moving at an absolute speed above 4,2 m/s) is optional. The
FVCWS warning is provided in accordance with the following functions.
5.4.1 Monitoring distance and relative speed between obstacle vehicle and subject vehicle
A forward obstacle vehicle is sensed by obstacle detecting devices such as optical (laser) radar, radio
wave radar, or image processing systems.
6 © ISO 2013 – All rights reserved

5.4.2 Judging the timing of collision
One possible way to judge the timing of a potential collision is by the results of evaluating the subject
vehicle speed, the distance to the obstacle vehicle, the relative speed between the subject vehicle and
the obstacle vehicle, and potentially the deceleration of the subject and the obstacle vehicles. When the
system detects multiple vehicles at the same time, it shall select the one in the subject vehicle expected
trajectory that the subject vehicle may collide with first if no action is taken as the obstacle vehicle.
5.4.3 Preliminary collision warning and Collision warning (see Annex A)
Forward vehicle collision warning systems shall provide a collision warning to the driver. A preliminary
collision warning is optional. The purpose of the preliminary collision warning is to inform the driver of
the presence of a potential forward collision hazard. In this case the driver should prepare to take the
necessary action to avoid a potential rear end collision. Even though the system is intended to provide
this warning prior to the collision warning, it is possible that rapidly changing conditions can occur
which result in the collision warning being issued without a preceding preliminary collision warning.
The purpose of the collision warning is to inform the driver of the need to take action in order to avoid
or reduce the severity of a possible imminent rear end collision.
Warnings consist of independent or combined use of visual, audible and/or tactile senses. However in
the case of a collision warning, a visual warning, as well as audible and/or tactile warning shall be
provided to the driver.
Warnings are issued depending on the relative speed between the subject vehicle and the obstacle
vehicle, the subject vehicle speed, the inter-vehicle distance, the free running (driver’s brake reaction)
time, and potentially the deceleration of the subject and the obstacle vehicles.
When the subject vehicle is approaching an obstacle vehicle, the warning distance should be decided
according to criteria with respect to required deceleration threshold values or their equivalents if other
warning triggering methods are used.
5.5 Warning elements requirements
5.5.1 FVCWS output
FVCWS shall provide a collision warning to the driver. A preliminary collision warning is optional.
5.5.2 Warning modality
5.5.2.1 FVCWS collision warning shall contain a visual warning, as well as an audible and/or haptic.
5.5.2.2 FVCWS preliminary collision warning shall contain visual or audible or a combination of visual
and audible modalities. Supplemental haptic modalities are optional for preliminary collision warning.
5.5.2.3 It is recommended that warning braking modality not be used for collision warning if the sub-
ject vehicle driver is applying the brakes.
5.5.2.4 The warning braking modality may be used for collision warning and preliminary collision
warning when automatic braking is applied in the subject vehicle (i.e. when automatic braking action
is underway).
5.5.2.5 Warning braking shall be applied for a duration that is less than 1 s. It shall result in a decelera-
tion less than 0,5 g, and a maximum speed reduction of 2 m/s. To ensure the effectiveness of the warning
braking, a minimum average deceleration of 0,1 g for a minimum duration of 100 ms shall be fulfilled.
5.5.2.6 Audible warning tone should be selected such that it can be easily heard and discriminated
from warnings unrelated to forward direction threats (e.g. lateral threat warnings).
5.5.2.7 An actuation of seat-belt pretensioner may be used for FVCWS collision warning.
5.5.3 Required deceleration threshold
5.5.3.1 FVCWS shall issue a collision warning when the required deceleration exceeds a threshold
value of A . The threshold value A shall not be greater than 0,68 g (considering the response time
req req
values in 5.5.4) in dry road and warm weather conditions.
5.5.3.2 FVCWS that provide a warning timing adjustment for the driver must have at least one setting
that satisfies the required deceleration threshold value A requirement in 5.5.3.1.
req
5.5.3.3 FVCWS may issue a preliminary collision warning at a lower required deceleration threshold.
5.5.3.4 The required deceleration threshold for collision and preliminary warnings may be adapted
based on the detected road condition, environmental and driver state conditions, driver behaviour and
different driving scenarios.
5.5.3.5 In case when automatic braking is applied in the subject vehicle, it is optional to modify A
req
such that its value exceeds the maximum deceleration capability of the active automatic braking system
(for example: ACC system).
5.5.4 Response times
5.5.4.1 The driver reaction time to the warning (driver brake reaction time (Tresp)) shall be incorpo-
rated in the calculation of the warning range. The Tresp value shall not be less than 0,8 s.
5.5.4.2 FVCWS that provide a warning timing adjustment for the driver must have a least one setting
that satisfies the Tresp requirement in 5.5.4.1.
5.5.4.3 The braking system response time (Tb) may be incorporated in the calculation of the required
deceleration. The selection of the braking system response time value is left to the FVCWS designer.
5.5.4.4 The driver brake reaction time (Tresp) and the braking system response time (Tb) may be set
to zero if the subject vehicle driver is applying the brakes.
5.5.4.5 In case when automatic braking is applied in the subject vehicle, the driver reaction time to
the warning [driver brake reaction time (Tresp)] may be set to zero in the calculation of the required
deceleration.
5.5.5 No Warning requirements
Subclause 5.5.5.1 states the condition when the FVCWS must not issue any type of warnings.
Subclauses 5.5.5.2 to 5.5.5.7 provide examples when the FVCWS warning may be suppressed or delayed.
5.5.5.1 The FVCWS shall not issue any type of warnings if the subject vehicle deceleration is greater
than or equal to the required deceleration threshold.
5.5.5.2 The FVCWS should not issue any type of warnings for a forward vehicle that is not in the lane
of the subject vehicle on roads with radius of curvature defined for each class in Table 1.
8 © ISO 2013 – All rights reserved

5.5.5.3 It is recommended that the FVCWS does not issue any type of warn
...