ISO 11067:2015

Intelligent transport systems - Curve speed warning systems (CSWS) - Performance requirements and test procedures

ISO 11067:2015 contains the basic warning strategy, minimum functionality requirements, basic driver interface elements, minimum requirements for diagnostics and reaction to failure, and performance test procedures for Curve Speed Warning Systems (CSWS). CSWS warns the driver against the danger caused by maintaining excessive speed to negotiate the upcoming curved roads, 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. It applies to vehicles with four or more wheels.

Systèmes intelligents de transport — Systèmes d'alerte de vitesse excessive en approche de virage (CSWS) — Exigences de performance et modes opératoires d'essai

General Information

• Status: Published
• Publication Date: 16-Jul-2015
• ICS: 03.220.20 - Road transport
• ICS: 35.240.60 - IT applications in transport
• Technical Committee: ISO/TC 204 - Intelligent transport systems
• Drafting Committee: ISO/TC 204/WG 14 - Vehicle/roadway warning and control systems
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2025
• Completion Date: 15-Oct-2025

Overview

ISO 11067:2015 - Intelligent transport systems - Curve speed warning systems (CSWS) - Performance requirements and test procedures - defines the minimum functionality, warning strategy, driver interface elements, diagnostics and failure reactions, and the performance test procedures for Curve Speed Warning Systems (CSWS). The standard applies to vehicles with four or more wheels and is focused on systems that warn drivers about excessive speed for upcoming curved roads; it does not mandate automated vehicle control. Responsibility for safe vehicle operation always remains with the driver.

Key topics and requirements

• Basic operation principle: how CSWS locates the vehicle relative to upcoming curved road sections and assesses collision risk based on curvature and vehicle speed.
• Warning threshold speed (V_WT): how the system determines the safe speed threshold for a given curvature point of interest and when a warning must be issued.
• Target curvature and look-ahead: methods to select the target curvature point of interest within the defined look ahead distance (S_LAD) and criteria for single, multiple and variable-radius curves.
• Timing and warning criteria: minimum curve speed warning time, warning end speed, warning distance and driver response time considerations.
• Driver interface and alerts: minimum driver interface capabilities including visual, audible and optional haptic elements, operation controls and system state transitions (on, off, unavailable, warning).
• Diagnostics and failure response: minimum requirements for detecting sensor/map/GNSS faults and transitioning to safe/unavailable states.
• Performance evaluation and test procedures: environmental, test-course and vehicle conditions, system installation/configuration and step-by-step performance tests.
• Definitions and calculation annexes: terms, symbols and informative annexes covering curve definitions, operation principles and calculation of parameters (e.g., minimum angle of curve).

Applications and who uses it

ISO 11067:2015 is intended for:

• Automotive OEMs and Tier‑1 suppliers designing CSWS hardware and software
• Intelligent Transport Systems (ITS) vendors integrating GNSS and digital-map data
• Test laboratories and certification bodies performing performance and compliance tests
• Road authorities and fleet operators evaluating safety features for vehicles (cars, vans, trucks, buses)
• Regulators and standards committees harmonizing vehicle safety and ITS specifications

Practical benefits include improving road safety by providing standardized warning behavior, consistent test methods for validation, and interoperability guidance for map/GNSS-based speed-warning implementations.

Related standards (if applicable)

ISO 11067:2015 was developed by ISO/TC 204 (Intelligent transport systems) and complements other ITS and vehicle safety standards addressing sensors, positioning, digital maps and human‑machine interface design. For implementation, coordinate with relevant ITS standards and national regulatory requirements.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11067
First edition
2015-07-15
Intelligent transport systems —
Curve speed warning systems (CSWS)
— Performance requirements and
test procedures
Systèmes intelligents de transport — Systèmes d’alerte de vitesse
excessive en approche de virage (CSWS) — Exigences de performance
et modes opératoires d’essai
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Symbols . 5
4 Classification . 6
5 Requirements . 6
5.1 Basic operation principle . 6
5.2 Functionality . 7
5.2.1 Basic system operation. 7
5.2.2 Determination of the target curvature point of interest . 7
5.2.3 Basic shape of a curved road . 8
5.2.4 Radius of curvature requirement for available state . 9
5.2.5 Determination of the warning threshold speed .10
5.2.6 Curve speed warning time requirements .10
5.2.7 Look ahead distance requirement .11
5.2.8 Appropriate warning for multiple curve .11
5.2.9 Optional functions of CSWS .12
5.3 Basic driver interface capabilities .13
5.3.1 Operation elements and system reactions .13
5.3.2 Haptic elements .13
5.4 Operational limits .13
6 Performance evaluation test methods .13
6.1 Test environmental conditions .13
6.2 Test course conditions .14
6.3 Test vehicle conditions .15
6.4 Test system installation and configuration .15
6.5 Test procedure .15
6.5.1 Parameters recoverable from data record .15
6.5.2 Detail test procedure .16
Annex A (informative) Definition of curves .19
Annex B (informative) Operation principles .22
Annex C (informative) Calculation of the minimum AOC .26
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 (see 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 (see 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.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information.
The committee responsible for this document is ISO/TC 204, Intelligent transport systems.
iv © ISO 2015 – All rights reserved

Introduction
The main function of Curve Speed Warning Systems (CSWS) is to warn the driver against the danger
caused by maintaining excessive speed to negotiate an upcoming curved road. The system computes the
current location of the vehicle with respect to the upcoming curved road of interest and determines a
warning threshold speed, below which the vehicle can safely negotiate the upcoming curves. If the vehicle
speed exceeds the warning threshold speed, the system provides a warning to the driver, prompting the
driver to react and lower the subject vehicle speed to a level suitable for negotiating the curved road
ahead. The CSWS scope does not include automated intervention features or means for controlling the
vehicle to match a desired speed.
INTERNATIONAL STANDARD ISO 11067:2015(E)
Intelligent transport systems — Curve speed warning
systems (CSWS) — Performance requirements and test
procedures
1 Scope
This International Standard contains the basic warning strategy, minimum functionality requirements,
basic driver interface elements, minimum requirements for diagnostics and reaction to failure, and
performance test procedures for Curve Speed Warning Systems (CSWS). CSWS warns the driver against
the danger caused by maintaining excessive speed to negotiate the upcoming curved roads, 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.
This International Standard applies to vehicles with four or more wheels.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
subject vehicle
vehicle equipped with the CSWS and related to the topic of discussion
2.2
subject vehicle speed
longitudinal component of the subject vehicle velocity
2.3
system states
one of several stages or phases of system operation
Note 1 to entry: See Figure 1.
2.3.1
CSWS off state
state in which CSWS is off
Note 1 to entry: This state has one of the following three causes: the driver has selected the off condition, the
ignition is off, or the CSWS is in failure.
2.3.2
CSWS on state
state in which CSWS is on
Note 1 to entry: This state is either in unavailable state or in available state.
2.3.3
CSWS unavailable state
system is in on state and the system has inadequate information
Note 1 to entry: The system cannot make a decision whether the warning criteria are met or not because of fault
in GNSS device, lack of map data, or other reasons.
2.3.4
CSWS available state
system is in on state and the system has sufficient information to make decisions on whether the
warning criteria are fulfilled or not
2.3.5
CSWS warning state
system is in available state and the warning criteria are all met
Note 1 to entry: The CSWS starts warning(s) or is operating the warning(s). The system periodically judges
whether the criteria are met in order to transition to the non-warning state.
2.3.6
CSWS non-warning state
system is in available state and the warning criteria are not all met
Note 1 to entry: The system periodically judges whether the criteria are met in order to transition to the warning state.
2.4
curved road
section where the radius of curvature is less than or equal to R
C
Note 1 to entry: R denotes the maximum radius of curvature to be regarded as a curvature point of interest for
C
potential warning for CSWS (see 5.2.2).
2.5
curvature point
arbitrary points on the curved road that has associated location and value of curvature
2.6
curvature point of interest
point of the curved road ahead where the distances from the subject vehicle to the curved roads are less
than the look ahead distance, S
LAD
2.7
curve start point
location where the radius of curvature of the curved roadway ahead becomes less than R
C
Note 1 to entry: See 5.2.3.
2.8
curve end point
location where the radius of curvature of the curved roadway ahead becomes ≥R
C
Note 1 to entry: See 5.2.3.
2.9
target curvature point of interest
particular curvature point of interest on the roadway of the subject vehicle that CSWS is about to provide
the warning to the driver
Note 1 to entry: CSWS selects the target curvature point of interest among the curvature points of interest and the
curvature point of interest may vary depending upon the distance from the current location of the subject vehicle
to the curvature point of interest and the current speed of the subject vehicle. If a section of the curved road has a
constant radius of the curvature, the curve start point becomes the target point of interest. See 5.2.2.
2.10
distance to curvature point of interest
S
current
distance from the current position of the subject vehicle to the curvature point of interest
2 © ISO 2015 – All rights reserved

2.11
time to curvature point of interest
t
TC
travel time from the current position of the subject vehicle to the curvature point of interest and
defined as follows
tS= V
TC current current
where
V is the current speed of the subject vehicle
current
2.12
warning threshold speed
V
WT
vehicle speed threshold that is used to determine if the CSWS warning is required
Note 1 to entry: If the vehicle speed measurement is greater than this threshold value, the CSWS provides the
warning to the driver. This threshold is below the maximum speed that is defined by designed lateral acceleration
to negotiate the upcoming curve.
2.13
warning end speed
V
WT_end
vehicle speed at which the CSWS transitions from CSWS warning state to CSWS non-warning so that the
CSWS ends the warning
2.14
warning distance
S
warn
distance from the location where the warning starts to the target curvature point of interest
2.15
driver response time
t
resp
reaction time of the driver which is the time from start of the speed changing event to the time that the
driver starts applying brake
2.16
minimum required deceleration
a
d_req
deceleration that, if constant, would enable the subject vehicle to match the warning threshold speed for
the target curvature point of interest
VV−
current WT
a =
d_req
2(×−St ×V )
current resp current
2.17
curve speed warning time
t
csw
time when the curve speed warning starts which is greater than or equal to the minimum allowed curve
speed warning time
tt≥
cswcsw_min
Note 1 to entry: The t , S , and V has the following relationship:
CSW warn current
tS= V
cswwarncurrent
Note 2 to entry: The value of t is selected by the manufacturer.
CSW
2.18
minimum allowed curve speed warning time
t
csw_min
lower threshold of the curve speed warning time
Note 1 to entry: The value of minimum allowed curve speed warning time is decided considering the amount of
overspeed of the subject vehicle and the reaction delay of drivers.
2.19
minimum operating speed
V
min
minimum subject vehicle speed at which the CSWS shall operate
2.20
maximum operating speed
V
max
maximum subject vehicle speed at which the CSWS shall operate
2.21
look ahead distance
S
LAD
curve detection range of the CSWS
Note 1 to entry: For the curvature points that have radius of curvature ≤R and the distances from the subject
C
vehicle to the curved roads are LAD
2.22
single curve
simple curved road with a constant radius of curvature separated from other curved roads
Note 1 to entry: The clothoid can be included.
2.23
multiple curve
curved road which is a combination of two or more closely located curved roads where the curved roads
are constant radius curvatures
Note 1 to entry: The clothoid can be included.
Note 2 to entry: See Table A.1.
2.24
variable radius curve
curved road with two or more radii of curvature in the same direction
Note 1 to entry: See Table A.1.
2.25
angle of curved road
AOC
central angle between the curve start point and the curve end point
Note 1 to entry: See 5.2.3 for illustrative description.
2.26
road shape points
points that is composing roads in digital map
Note 1 to entry: Roads are composed of points and links which reflect the shape and position of the road in
the digital map.
4 © ISO 2015 – All rights reserved

3 Symbols
a minimum required deceleration (m/s )
d_req
a maximum braking deceleration (m/s )
d_max
a maximum value of the lateral acceleration threshold from which vehicles may deviate on a
lateral_max
curved roadway (m/s )
d on the section of a curved road, the maximum distance from the point on the line consist-
max
ing of two neighbouring road shape points to the point on the arc of the section (m)
G gravitational acceleration (m/s )
R radius of curvature at a point along a curved roadway (m)
R threshold radius of curvature to define a curvature point of interest; the curvature point
C
of interest is reached if the radius of the curvature of the particular location is less than R
C
(m)
R upper threshold of the operational range in terms of the radius of curvature (m)
max
R lower threshold of the operational range in terms of the radius of curvature (m)
min
S distance to the curvature point of interest (m)
current
S look ahead distance (m)
LAD
S warning threshold distance considering V and t (m)
warn current CSW
S minimum of warning threshold distance considering V and t (m)
warn_min current CSW_min
V additional speed considering the tolerance for the test (m/s)
add
V current speed of the subject vehicle (m/s)
current
V minimum operating speed of CSWS (m/s)
min
V maximum operating speed of CSWS (m/s)
max
V test vehicle speed (m/s)
test
V warning threshold speed (m/s)
WT
V warning end speed (m/s)
WT_end
V upper threshold of the warning threshold speed (m/s)
WT_max
t curve speed warning time (s)
CSW
t minimum allowed curve speed warning time (s)
CSW_min
t minimum reaction delay (s)
d_min
t time to curvature point of interest (s)
TC
t driver response time (s)
resp
θ angle of curved road (AOC) (deg)
θ minimum AOC (deg)
min
4 Classification
The CSWS subject to this International Standard only has a single type.
5 Requirements
5.1 Basic operation principle
Figure 1 — CSWS states and transitions
The pattern of the transition conditions are as follows.
— The condition that CSWS transitions from system OFF state to system ON state are as follows.
a) For CSWS ON/OFF control equipped vehicles, both the vehicle ignition and the ON/OFF
control are on.
b) For CSWS ON/OFF control not equipped vehicles, the vehicle ignition is on.
c) The transition from CSWS OFF to CSWS ON can be performed by the driver or automatically.
— The condition that CSWS transitions from system ON state to system OFF state are as follows.
a) For CSWS ON/OFF control equipped vehicles, either the vehicle ignition or the ON/OFF
control are off.
b) For CSWS ON/OFF control not equipped vehicles, the vehicle ignition is off.
c) If the system is in on state and a system failure occurs.
CSWS shall, as a minimum, provide the following operations and state transitions. The following
constitutes the fundamental behaviour of CSWS. The warning criteria are described in 5.2.1.
— In CSWS available state, the system judges the warning criteria to determine whether the warning
should be issued. If the system judges to warn, the CSWS starts warning(s) immediately.
— In CSWS unavailable state, the warning judgment is not made because the warning criteria such as
subject vehicle position are being monitored by CSWS but not confirmed in this state.
— In CSWS non-warning state, the system shall evaluate the activation criteria. CSWS shall not perform
any warning actions.
— If the activation criteria are met, the system shall transition from CSWS non-warning state to CSWS
warning state. This transition shall be automatic.
6 © ISO 2015 – All rights reserved

— If the activation criteria are not met, the system shall transition from CSWS warning state to CSWS
non-warning state.
— The system may be fitted with a system ON/OFF control that can be operated by the driver at all times.
5.2 Functionality
CSWS consists of means to determine the radius of curvature of the road, means to acquire relative position
of the subject vehicle from the curvature point of interest, means to acquire the vehicle speed, means to
judge the critical speed of the curvature point of interest, and means to provide warning to the driver.
The functional requirements of CSWS are described as follows.
5.2.1 Basic system operation
The basic system operation of CSWS is described in this subclause.
— When the CSWS is in the CSWS available state, the system acquires the warning threshold speed,
V , the current speed of the subject vehicle, V , the distance to the curvature point of interest,
WT current
S , and the distance where the warning shall be started, S . If V exceeds V and
current warn current WT
S is less than S , the system regards the curvature point of interest as a target curvature
current warn
point of interest and transitions from non-warning state to CSWS warning state.
V > V and S < S : CSWS non-warning state to warning state
current WT current warn
— When the CSWS is in the CSWS warning state, the system provides warning to the driver so that the
driver may reduce the vehicle speed. When V becomes less than V or S becomes
current WT_end current
greater than S , the system automatically transitions from warning state to non-warning state.
warn
V < V or S > S : CSWS warning state to non-warning state
current WT_end current warn
where V can be adopted to avoid possible chattering of the CSWS and is selected by
WT_end
manufacturers according to the following formula.
NOTE The value of the V can be same as V .
WT_end WT
VV≥
WT WT_end
S and S can be defined as follows for better understanding.
warn warn_min
SV=×t
warn current csw
SV=×t
warn_min current csw_min
— The CSWS may suppress the warning when the driver is braking.
5.2.2 Determination of the target curvature point of interest
The conditions to meet in order to be the curved road, the curvature point of interest, and the target
curvature points of interest are described as follows. Detail descriptions and figures can be found in A.1.
— Non-curvature point: location on a road with a radius of curvature greater than R . This location of
C
the road has no potential to be a curvature point of interest and regarded as a non-curvature point
as shown in Figure A.1.
R > R : Non-curvature point
C
— Curvature point of interest: location on a road with the radius of curvature less than or equal to R
C
and the distance from the current location of the subject vehicle to a curve start point is less than
the look ahead distance, S , as shown in Figure A.1 and Figure A.3.
LAD
R ≤ R and S < S : Curvature point of interest
C current LAD
— Target curvature point of interest: particular curvature points of interest on the roadway of the
subject vehicle that CSWS is about to provide the warning to the driver. CSWS selects the target
curvature points of interest among the curvature points of interest and the target curvature point
of interest may vary depending upon the distance from the current location of the subject vehicle to
the curvature point of interest and the vehicle speed. If a section of the curved road has a constant
radius of the curvature, the curve start point becomes the target curvature point of interest.
V > V and S < S : Target curvature point of interest
current WT current warn
Figure 2 — Definitions of curvature points of interest and the target curvature points of interest
5.2.3 Basic shape of a curved road
The basic shape of a curved road is described in this subclause for defining the curved road in the
perspective of CSWS.
— A single curve with constant radius is shown in Figure 3 as an example of a simple curved road. The
curved road described here starts from clothoid curve and it has a curve with constant radius.
Figure 3 — Basic shape of a single curve with constant radius
8 © ISO 2015 – All rights reserved

— The curved road starts from the point that the radius of curvature becomes less than or equal to the
threshold radius of curvature, R . This point is defined as a curve start point. On a curve of interest,
C
there can be many curvature points of interest as shown in Figure 4 and Figure 5.
— The curved road ends at the point where the radius of curvature becomes greater than the threshold
radius of curvature, R .
C
— For curves with a constant radius, the curve start point can be a potential target curvature point. For
the curves with multiple radii of curvature, the target curvature point is defined depending upon the
warning distance and warning threshold speed of each curvature point of interest. Determination of
target curvature point on curves with multiple radius of curvature is described in A.1.
Figure 4 — Basic shape of a curved road in terms of 1/R
Figure 5 — Curve start point for different curved roads
5.2.4 Radius of curvature requirement for available state
The radius of curvature for available state has the following requirements.
— The calculating method of the radius of curvature lies in the responsibility of manufacturers.
...