ISO 17387:2026

Intelligent transport systems — Lane change decision aid systems (LCDAS) — Performance requirements and test procedures

This document specifies system requirements and test methods for lane change decision aid systems (LCDAS). LCDAS are intended to warn the driver of the subject vehicle against potential collisions with vehicles either to the side or to the rear in the adjacent lanes of the subject vehicle and moving in the same direction as the subject vehicle for lane change manoeuvres. This document addresses LCDAS for use on forward-moving cars, vans and straight trucks. This document does not address LCDAS for use on motorcycles or articulated vehicles such as tractor/trailer combinations and articulated buses.

Systèmes de transport intelligents — Systèmes d'aide à la décision de changement de voie (LCDAS) — Exigences de performances et méthodes d'essai

General Information

• Status: Published
• Publication Date: 19-Feb-2026
• 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: 6060 - International Standard published
• Start Date: 20-Feb-2026
• Due Date: 31-Oct-2026
• Completion Date: 20-Feb-2026

Relations

• Revises: ISO 17387:2008 - Intelligent transport systems — Lane change decision aid systems (LCDAS) — Performance requirements and test procedures
• Effective Date: 04-Nov-2023

Overview

ISO 17387:2026 sets out the performance requirements and test procedures for Lane Change Decision Aid Systems (LCDAS) within the framework of intelligent transport systems (ITS). LCDAS are electronic driver assistance systems designed to warn drivers of potential collisions with vehicles approaching from the side or rear in adjacent lanes during lane change maneuvers. This standard establishes the minimum system functions and testing protocols required for cars, vans, and straight trucks. Notably, it does not include guidelines for motorcycles, articulated trucks, or buses with trailers.

The primary goal of this standard is to increase road safety by reducing accidents caused by unsafe lane changes. By standardizing performance and evaluation methods, ISO 17387:2026 ensures that LCDAS technologies provide reliable and consistent warnings, thereby supporting safer driving decisions and complementing traditional vehicle mirrors.

Key Topics

• System Types and Functions

  • Type I: Blind spot warning for adjacent zones
  • Type II: Closing vehicle warning for rear zones
  • Type III: Combined warnings for blind spots and rear closing vehicles

• Coverage Zone Classification

  • Defines the minimum detection areas beside and behind the subject vehicle
  • Specifies adjacent and rear zones coverage, independent of road markings

• Performance Requirements

  • Minimum detectable target vehicle size
  • Sensor coverage and warning response times
  • Lateral and rear clearance definitions
  • Activation and warning criteria (e.g., based on vehicle speed, turn signals, or driver steering input)

• System State and Warning Hierarchy

  • Inactive, active, and multiple warning states, including different warning levels based on urgency and driver intention

• Test Procedures

  • Standardized protocols for evaluating blind spot, closing vehicle, and lane change warnings
  • Procedures for environmental conditions and self-testing requirements

• Classification by Target Closing Speed and Road Curvature

  • System capabilities related to maximum vehicle closing speeds (SAV, MAV, FAV)
  • Optional classifications for system performance on curved roads (Type A, B, C based on minimum radius of curvature)

Applications

Lane Change Decision Aid Systems (LCDAS) play a critical role in embedded automotive safety features for:

• Passenger Cars and Vans: Offers real-time warnings during lane change maneuvers, enabling drivers to avoid collisions in heavy traffic or on multi-lane highways.
• Light and Medium-Duty Trucks: Improves safety when visibility is limited due to vehicle size and blind spots.
• Commercial Fleets: Supports fleet operators in meeting safety compliance, reducing accident rates, and improving driver confidence.

LCDAS, as standardized by ISO 17387:2026, are especially valuable in:

• Urban traffic environments with frequent lane changes
• Highway driving where speed differentials pose higher collision risks
• Advanced driver assistance systems (ADAS), serving as a foundational technology for partially automated vehicles

Manufacturers, automotive engineers, and regulatory bodies can use this standard to guide the design, development, and certification of electronic safety systems, ensuring cross-market compatibility and effective risk mitigation.

Related Standards

• ISO 26262 - Road vehicles - Functional safety requirements for electronic systems
• ISO 21434 - Road vehicles - Cybersecurity engineering for road vehicles
• ISO 15623 - Forward vehicle collision warning systems - Performance requirements
• SAE J2012 - Diagnostic trouble code definitions
• UNECE Regulation No. 151 - Blind Spot Information Systems

By adhering to ISO 17387:2026, organizations can align LCDAS technologies with broader ITS and ADAS standards, providing integrated and reliable solutions that meet international safety and performance expectations.

Keywords: intelligent transport systems, LCDAS, lane change assistance, blind spot warning, automotive safety, ISO 17387:2026, driver warning systems, vehicle collision avoidance, test procedures, performance requirements.

Standards Content (Sample)

International
Standard
ISO 17387
Second edition
Intelligent transport systems —
2026-02
Lane change decision aid
systems (LCDAS) — Performance
requirements and test procedures
Systèmes de transport intelligents — Systèmes d'aide à la
décision de changement de voie (LCDAS) — Exigences de
performances et méthodes d'essai
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification . 4
4.1 Coverage zone classification .4
4.1.1 General .4
4.1.2 Type I systems .4
4.1.3 Type II systems .5
4.1.4 Type III systems .5
4.2 Target vehicle closing speed classification .5
4.3 Optional target vehicle closing speed classification for road curvature .6
4.3.1 Overview .6
4.3.2 Type A systems .7
4.3.3 Type B systems .7
4.3.4 Type C systems .8
5 Functional requirements . 9
5.1 LCDAS state diagram .9
5.1.1 General .9
5.1.2 LCDAS inactive state .9
5.1.3 Activation criteria .9
5.1.4 LCDAS active state .10
5.2 System performance .11
5.2.1 General .11
5.2.2 Minimum detectable target vehicle . 12
5.2.3 Requirements for the blind spot warning function . 13
5.2.4 Requirements for the closing vehicle warning function .14
5.2.5 Requirements for the lane change warning function .16
5.2.6 System response time .17
5.3 User interface .17
5.3.1 LCDAS status indication .17
5.3.2 LCDAS warning indication .17
5.3.3 LCDAS failure indication .17
5.4 Operation with trailers .18
5.5 Self-test requirements .18
6 Test requirements .18
6.1 Test target vehicle .18
6.2 Environmental conditions . .18
6.3 Blind spot warning test requirements .18
6.3.1 General .18
6.3.2 Blind spot warning test measurement system .18
6.3.3 Blind spot warning test procedures .19
6.4 Closing vehicle warning test requirements . 25
6.4.1 General . 25
6.4.2 Closing vehicle warning test measurement system . 25
6.4.3 Closing vehicle warning test procedures . 26
6.5 Lane change warning test requirements .31
6.5.1 General .31
6.5.2 Lane change warning test measurement system .31
6.5.3 Lane change warning test procedures .32
Annex A (informative) Blind spot warning example cases.37

iii
Annex B (informative) Closing vehicle warning test speeds for systems with optional curvature
types .45
Bibliography .46

iv
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,
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had received notice of (a)
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Any trade name used in this document is information given for the convenience of users and does not
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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical CommitteeISO/TC 204, Intelligent transport systems.
This second edition cancels and replaces the first edition (ISO 17387:2008), which has been technically
revised.
The main changes are as follows:
— the target vehicle closing speed classification and target vehicle closing speed classification for road
curvature have been modified;
— the test procedure for closing vehicle warning function has been modified;
— the blind spot warning test for target vehicle moving laterally has been modified;
— the definition of the reference point for driver’s eye position has been simplified.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
Introduction
Lane change decision aid systems (LCDAS) warn the driver against collisions that can occur due to a lane
change manoeuvre. LCDAS are intended to supplement the vehicle’s interior and exterior rear-view mirrors;
they are not intended to eliminate the need for such mirrors. LCDAS are intended to detect vehicles in the
adjacent lanes to the rear and sides of the subject vehicle (see Figure 1). When the subject vehicle driver
indicates the desire to make a lane change, the system evaluates the situation and warns the driver if a
lane change is not recommended. The absence of a warning does not guarantee that the driver can safely
make a lane change manoeuvre. The system will not take any automatic action to prevent possible collisions.
Responsibility for the safe operation of the vehicle remains with the driver.
NOTE Many figures in this document show vehicles on roadways with lane markings. This is not intended to imply
that lane marking recognition or lane detection is required for an LCDAS. The lane markings are drawn for reference
only.
Key
1 subject vehicle
2 target vehicles
a
The shaded area illustrates the concept of one possible system. The actual requirements are given in Clause 5.
Figure 1 — LCDAS concept
vi
International Standard ISO 17387:2026(en)
Intelligent transport systems — Lane change decision aid
systems (LCDAS) — Performance requirements and test
procedures
1 Scope
This document specifies system requirements and test methods for lane change decision aid systems
(LCDAS). LCDAS are intended to warn the driver of the subject vehicle against potential collisions with
vehicles either to the side or to the rear in the adjacent lanes of the subject vehicle and moving in the same
direction as the subject vehicle for lane change manoeuvres. This document addresses LCDAS for use on
forward-moving cars, vans and straight trucks.
This document does not address LCDAS for use on motorcycles or articulated vehicles such as tractor/trailer
combinations and articulated buses.
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 terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
subject vehicle
vehicle equipped with the system in question and related to the topic of discussion
3.2
target vehicle
any vehicle that is closing in on the subject vehicle from behind, or any
vehicle that is located in one of the adjacent zones
3.3
coverage zone
entire area to be monitored by the lane change decision aid system (LCDAS), consisting of a specific subset
of the following zones: left adjacent zone, right adjacent zone, left rear zone and right rear zone
Note 1 to entry: A target vehicle located within the coverage zone will thus be detected by the system.
3.4
adjacent zone
zone to the left and right of the subject vehicle
Note 1 to entry: See Figure 2. This figure shows the zone concept only. Actual requirements are given in 5.2.

Note 2 to entry: The adjacent zones are intended to cover the lanes adjacent to the subject vehicle. However, the
position and size of the adjacent zones are defined with respect to the subject vehicle and are independent of any lane
markings.
Key
1 subject vehicle
2 left adjacent zone
3 right adjacent zone
Figure 2 — Adjacent zones
3.5
rear zone
zone that is behind and to the sides of the subject vehicle
Note 1 to entry: See Figure 3. This figure shows the zone concept only. Actual requirements are given in 5.2.
Note 2 to entry: The rear zones are intended to cover the lanes adjacent to the subject vehicle. However, the position
and size of the rear zones are defined with respect to the subject vehicle and are independent of any lane markings.
Key
1 subject vehicle
2 left rear zone
3 right rear zone
Figure 3 — Rear zones
3.6
lateral clearance
lateral distance between the side of the subject vehicle and the near side of a target
vehicle
Note 1 to entry: See Figure 4.

Key
1 subject vehicle
2 target vehicle
3 lateral clearance
Figure 4 — Lateral clearance
3.7
rear clearance
distance between the rear of the subject vehicle and the front of the target vehicle as
measured along a straight line, or optionally, as estimated along the target vehicle’s estimated path
Note 1 to entry: See Figure 5.
Note 2 to entry: This definition applies to target vehicles in the rear zones only.
a) On a straight road measured along b) On a straight road estimated along
a straight line target vehicle path
Key
1 subject vehicle
2 target vehicle
3 rear clearance
Figure 5 — Examples of rear clearance
3.8
closing speed
difference between the target vehicle’s speed and the subject vehicle’s speed
Note 1 to entry: This definition applies to target vehicles in the rear zones only. A positive closing speed indicates that
the target vehicle is closing in on the subject vehicle from the rear.
3.9
time to collision
estimated time that it would take a target vehicle to collide with the subject vehicle if the subject vehicle
were in the target vehicle’s path and the target vehicle’s current closing speed were to remain constant
Note 1 to entry: Time to collision can be estimated by dividing a target vehicle’s rear clearance by its closing speed.
This definition applies to target vehicles in the rear zones only.

3.10
overtaking speed
difference between the subject vehicle’s speed and the target vehicle’s speed when
the subject vehicle is overtaking the target vehicle
Note 1 to entry: A positive overtaking speed indicates that the subject vehicle is moving faster than the target vehicle.
3.11
blind spot warning function
function that detects the presence of target vehicles in one or more of the adjacent zones and provides a
warning to the subject vehicle driver
3.12
closing vehicle warning function
function that detects closing vehicles in one or more of the rear zones and provides a warning to the driver
3.13
lane change warning function
function that combines the blind spot warning function and the closing vehicle warning function
3.14
roadway radius of curvature
horizontal radius of curvature of the road on which the subject vehicle is travelling
3.15
straight road
segment of road for which the curve radius is larger than 5 000 m
3.16
reference point for driver’s eye position
reference for the position of driver’s eyes in longitudinal direction of the subject vehicle
Note 1 to entry: The reference point is located at the centre of the 95th percentile eyellipse on the x-axis of the subject
vehicle.
4 Classification
4.1 Coverage zone classification
4.1.1 General
LCDAS are classified by the minimum required coverage as shown in Table 1. For example, a type I system
shall provide coverage of at least the left and right adjacent zones.
Table 1 — Coverage zone classification
Left adjacent Right adjacent Left rear Right rear
Type Function
zone coverage zone coverage zone coverage zone coverage
Blind spot
I X X
warning
Closing vehicle
II X X
warning
Lane change
III X X X X
warning
4.1.2 Type I systems
Type I systems provide the blind spot warning function only. Type I systems are intended to warn the subject
vehicle driver of target vehicles in the adjacent zones. Type I systems are not required to provide warnings

of target vehicles that are approaching the subject vehicle from the rear. The subject vehicle driver shall
be made aware of the limitations of this type of system, at least in the owner’s manual. In particular, the
owner’s manual shall include the following statement: “This system provides support only within a limited
area beside the vehicle. The system will not necessarily provide adequate warning for vehicles approaching
from the rear.”
4.1.3 Type II systems
Type II systems provide the closing vehicle warning function only. These systems are intended to warn the
subject vehicle driver of target vehicles that are approaching the subject vehicle from the rear. Since type II
systems are not required to provide warnings of target vehicles located adjacent to the subject vehicle,
type II systems are recommended for use on vehicles that have side mirrors with a horizontal field of view
of at least 45° on both sides of the vehicle. If type II systems are used on other vehicles, the owner’s manual
should include the following statement: “The driver is required to turn and look into the adjacent area
before attempting a lane change.” The subject vehicle driver shall be made aware of the limitations of this
type of system, at least in the owner’s manual. In particular, the owner’s manual shall include the following
statement: “This system provides no support for the areas adjacent to the subject vehicle. This system will
not necessarily provide adequate warning for very fast moving vehicles approaching from the rear and will
not necessarily not cover the detection of approaching vehicles in all road curvatures.”
4.1.4 Type III systems
Type III systems provide the blind spot warning function and the closing vehicle warning function. Type III
systems are intended to warn the subject vehicle driver of target vehicles in the adjacent zones and target
vehicles which are approaching the subject vehicle from the rear. The subject vehicle driver shall be made
aware of the limitations of this type of system, at least in the owner’s manual. In particular, the owner’s
manual shall include the following statement: “This system will not necessarily provide adequate warning
for very fast moving vehicles approaching from the rear and will not necessarily cover the detection of
approaching vehicles in all road curvatures.”
4.2 Target vehicle closing speed classification
LCDAS of types II and III are classified based on the maximum approaching target vehicle closing speed
shown in Table 2. A system may belong to more than one of the types listed in Table 2. For example, a highly
capable system may meet or exceed the minimum requirements defined individually for types SAV, MAV and
FAV.
Table 2 — Target vehicle closing speed classification
Maximum target vehicle
closing speed
Type
m/s
SAV 10
MAV 15
FAV 20
NOTE The maximum target vehicle closing speed has a direct effect on the required sensor range and/or
acquisition time. A higher closing speed will require a longer sensor range and/or a shorter acquisition time in order
to detect the target vehicle in sufficient time to give the subject vehicle driver adequate warning.
Figure 6 shows the minimum performance of type SAV, MAV and FAV regarding the relative speed between
the subject vehicle and the target vehicle. LCDAS of types II and III can be capable of operating on curved
roads. There is a relationship between the maximum target vehicle closing speed and the roadway radius of
curvature. For a given curve radius and a typical subject vehicle speed, the closing speed of a target vehicle
is limited by driving dynamics parameters. In addition, the visibility of the target vehicle can be limited due
to the curve radii.
The subject vehicle driver shall be made aware of the limitations of the system, at least in the owner’s manual.
In particular, the owner’s manual shall include the following statement: “This system will not necessarily
provide adequate warning on curves."
Key
X target vehicle closing speed, m/s
1 type SAV - slow
2 type MAV - medium
3 type FAV - fast
Figure 6 — Type SAV, MAV, FAV system minimum performance regarding to target vehicle closing
speed
4.3 Optional target vehicle closing speed classification for road curvature
4.3.1 Overview
In addition to the target vehicle closing speed classification (SAV, MAV or FAV) as shown in Figure 6,
curvature capability provided by LCDAS can also be provided.
An advanced form of LCDAS may use additional sensor input or may integrate additional environmental
information from a map. Such systems can provide the closing vehicle warning function in curvature
situations.
For conformity to this optional classification, roadway curvature shall be related to the expectable maximum
target vehicle closing speed, shown in Table 3.
Types A, B and C represent the relationship between LCDAS types SAV, MAV and FAV in addition to a
minimum roadway curvature:
— type A contains type SAV;
— type B contains type SAV and MAV;
— type C contains type SAV, MAV and FAV.
Table 3 — Target vehicle closing speed classification for road curvature
Maximum target vehicle Minimum roadway radius
closing speed of curvature
Type
m/s m
A 10 125
B 15 250
C 20 500
4.3.2 Type A systems
Figure 7 shows the minimum required region of performance with regard to roadway radius of curvature
and target vehicle closing speed for a type A system. Type A systems can be capable of operating on curved
roads with smaller radii. The subject vehicle driver shall be made aware of the limitations of the system, at
least in the owner’s manual. In particular, the owner’s manual shall include the following statement: “This
system will not necessarily provide adequate warning on curves tighter than [X] metres radius,” where X is
replaced by the tightest curve radius for which the system is designed but not more than 125 m.
Key
X target vehicle closing speed, m/s
Y roadway radius of curvature, m
Figure 7 — Type A system minimum region of performance
4.3.3 Type B systems
Figure 8 shows the minimum required region of performance with regard to roadway radius of curvature
and target vehicle closing speed for a type B system. Type B systems can be capable of operating on curved
roads with smaller radii. The subject vehicle driver shall be made aware of the limitations of the system, at
least in the owner’s manual. In particular, the owner’s manual shall include the following statement: “This
system will not necessarily provide adequate warning on curves tighter than [X] metres radius” where X is
replaced by the tightest curve radius for which the system is designed but not more than 250 m.

Key
X target vehicle closing speed, m/s
Y roadway radius of curvature, m
Figure 8 — Type B system minimum region of performance
4.3.4 Type C systems
Figure 9 shows the minimum required region of performance with regard to roadway radius of curvature
and target vehicle closing speed for a type C system. Type C systems can be capable of operating on curved
roads with smaller radii. The subject vehicle driver shall be made aware of the limitations of the system, at
least in the owner’s manual. In particular, the owner’s manual shall include the following statement: “This
system will not necessarily provide adequate warning on curves tighter than [X] metres radius” where X is
replaced by the tightest curve radius for which the system is designed but not more than 500 m.
Key
X target vehicle closing speed, m/s
Y roadway radius of curvature, m
Figure 9 — Type C system minimum region of performance

5 Functional requirements
5.1 LCDAS state diagram
5.1.1 General
At a minimum, the LCDAS shall operate according to the state diagram in Figure 10.
Figure 10 — LCDAS state diagram
5.1.2 LCDAS inactive state
In the LCDAS inactive state the system shall give no warnings to the driver. This state may be a power off
state or a ready state. In a ready state the system can detect target vehicles, but shall not issue warnings
because the activation criteria are not met.
5.1.3 Activation criteria
5.1.3.1 General
When activated, the LCDAS shall transition from the LCDAS inactive state to the LCDAS active state. Several
activation criteria may be used at the same time. Potential activation criteria include but are not limited to
those described in the following subclauses.
5.1.3.2 Continuous activation
The system may be active continuously (whenever the subject vehicle’s ignition is on).
5.1.3.3 Manual switch activation
The system may be activated manually, e.g. by a toggle switch, a tip switch or a menu-based user interface.
5.1.3.4 Turn signal activation
The system may be activated based on the subject vehicle turn signal status. For instance, if the left turn
signal is on, the system may be activated on the left side of the subject vehicle, while remaining inactive on
the right side of the subject vehicle.

5.1.3.5 Subject vehicle speed activation
The system may be activated based on the subject vehicle speed. If this is the case, then when the subject
vehicle speed is greater than or equal to a certain threshold speed the system will transition to the LCDAS
active state. The threshold speed shall be not more than 16,7 m/s (60 km/h).
For blind spot warning function, the threshold speed should be no more than 8,3 m/s (30 km/h) to cover
urban traffic situations.
5.1.4 LCDAS active state
5.1.4.1 General
In the LCDAS active state the system shall detect target vehicles.
5.1.4.2 Non-warning state
In the non-warning state, the system is active, but the warning requirements are not fulfilled.
5.1.4.3 Warning state
5.1.4.3.1 General
In the warning state the system is active, and the warning requirements are fulfilled.
5.1.4.3.2 Warning level 1 state
In the warning level 1 state the warning requirements are fulfilled but no evaluation criteria are met.
The warning given to the driver in this state shall be a cautionary warning, which is less urgent than the
warnings given in warning level 2 and any subsequent warning levels.
5.1.4.3.3 Evaluation criteria
5.1.4.3.3.1 General
Evaluation criteria are certain parameters that an LCDAS may monitor. Evaluation criteria should be useful
in determining the driver’s intention for changing the lane of travel. If one or more of these evaluation
criteria are met, then the system may transition from the warning level 1 state to warning level 2 and above.
Several evaluation criteria may be used at the same time. Potential evaluation criteria include but are not
limited to those described in the following subclauses.
5.1.4.3.3.2 Turn signal evaluation
The system may evaluate the subject vehicle turn signal status. For instance, if the left turn signal is on, the
system may transition to warning level 2 or higher on the left side of the subject vehicle, while not affecting
the right side of the subject vehicle.
5.1.4.3.3.3 Subject vehicle steering input evaluation
The system may evaluate the steering input by the subject vehicle driver. If, for instance, the system
determines that the driver is initiating a lane change to the left, the system may transition to warning level 2
or higher on the left side of the subject vehicle, while not affecting the right side of the subject vehicle.
5.1.4.3.3.4 Subject vehicle lane position evaluation
The system may evaluate the subject vehicle’s position and/or lateral motion within its lane. If, for instance,
the system determines that the subject vehicle is moving toward or into the lane to the left, the system may

transition to warning level 2 or higher on the left side of the subject vehicle, while not affecting the right side
of the subject vehicle.
5.1.4.3.3.5 Lateral clearance evaluation
The system may evaluate the lateral clearance to a target vehicle. If the system has the ability to measure
lateral clearance, then when the lateral clearance is less than a preset threshold value, the system may
transition to warning level 2 or higher.
5.1.4.3.4 Warning level 2 and above
Warning level 2 and above are optional states. In these states the warning requirements are fulfilled, and
one or more evaluation criteria are met. The warnings given to the driver in these states shall be imminent
warnings that are more urgent than the warning given in the warning level 1 state.
5.2 System performance
5.2.1 General
Lines A – O, illustrated in Figure 11 and defined in the following list, are necessary for the description of the
blind spot warning requirements and the closing vehicle warning requirements. The designations "right",
"left" and "behind" refer to the driving direction of the subject vehicle. The lane markings in Figure 11 are
shown for reference only. All dimensions are given with respect to the subject vehicle.
— Line A shall be parallel to the trailing edge of the subject vehicle, with a distance of 30,0 m behind it.
— Line B shall be parallel to the trailing edge of the subject vehicle, with a distance of 3,0 m behind it.
— Line C shall be parallel to the leading edge of the subject vehicle and 85 cm behind the centre of the
braking pedal on x-axis of the vehicle (longitudinal) representing a reference point for driver’s eye
position.
— Line D shall be the extension in both directions of the leading edge of the subject vehicle.
— Line E shall be parallel to the centreline of the subject vehicle and shall be located at the left outermost
edge of the subject vehicle’s body, excluding the exterior mirror.
— Line F shall be parallel to the centreline of the subject vehicle, at a distance of 0,5 m to the left of the left
outermost edge of the subject vehicle’s body.
— Line G shall be parallel to the centreline of the subject vehicle, at a distance of 3,0 m to the left of the left
outermost edge of the subject vehicle’s body.
— Line H shall be parallel to the centreline of the subject vehicle, at a distance of 6,0 m to the left of the left
outermost edge of the subject vehicle’s body.
— Line J shall be parallel to the centreline of the subject vehicle and shall be located at the right outermost
edge of the subject vehicle’s body, excluding the exterior mirror.
— Line K shall be parallel to the centreline of the subject vehicle, at a distance of 0,5 m to the right of the
right outermost edge of the subject vehicle’s body.
— Line L shall be parallel to the centreline of the subject vehicle, at a distance of 3,0 m to the right of the
right outermost edge of the subject vehicle’s body.
— Line M shall be parallel to the centreline of the subject vehicle, at a distance of 6,0 m to the right of the
right outermost edge of the subject vehicle’s body.
— Line N shall be the extension in both directions of the trailing edge of the subject vehicle.
— Line O shall be parallel to the trailing edge of the subject vehicle, at a distance of 10,0 m behind it.

Key
1 subject vehicle
2 reference point for driver’s eye position
3 left adjacent zone
4 right adjacent zone
Figure 11 — Warning requirements diagram
5.2.2 Minimum detectable target vehicle
The LCDAS shall be capable of detecting target vehicles that are at least the size of a highway-legal motorcycle
with a rider.
5.2.3 Requirements for the blind spot warning function
5.2.3.1 Warning requirements for the blind spot warning function
5.2.3.1.1 General
The blind spot warning function shall provide coverage of the left and right adjacent zones. The minimum
requirement is to warn on a straight road. Means should be considered to avoid false warnings on
curved roads. The lines illustrated in Figure 11 are needed for the description of the blind spot warning
requirements.
NOTE The adjacent zone coverage is intended to supplement the mirror coverage of the subject vehicle.
5.2.3.1.2 Left side blind spot warning requirements
Referring to Figure 11, a left side blind spot warning shall be issued to the subject vehicle driver if a target
vehicle satisfies all of the following conditions:
— any part of the target vehicle is in front of line B;
— the target vehicle is entirely behind line C;
— the target vehicle is entirely to the left of line F;
— any part of the target vehicle is to the right of line G.
If the zone defined by lines A, D, E and H contains neither target vehicles nor any parts thereof, then a left
side blind spot warning shall not be issued.
See Annex A for blind spot warning example cases.
5.2.3.1.3 Right side blind spot warning requirements
Referring to Figure 11, a right side blind spot warning shall be issued to the subject vehicle driver if a target
vehicle satisfies all of the following conditions:
— any part of the target vehicle is in front of line B;
— the target vehicle is entirely behind line C;
— the target vehicle is entirely to the right of line K;
— any part of the target vehicle is to the left of line L.
If the zone defined by lines A, D, J and M contains neither target vehicles nor any parts thereof, then a right
side blind spot warning shall not be issued.
See Annex A for blind spot warning example cases.
5.2.3.2 Optional blind spot warning suppression
If the subject vehicle is overtaking the target vehicle and the target vehicle has entered the adjacent zone
from the front, the blind spot warning may be suppressed for a period of no more than 2 s after the blind
spot warning is first required.

5.2.4 Requirements for the closing vehicle warning function
5.2.4.1 Warning requirements for the closing vehicle warning function
5.2.4.1.1 General
The closing vehicle warning function shall provide coverage of the left and right rear zones. The minimum
requirement is to warn on a straight road. Means should be considered to avoid false warnings on curved
roads. The lines illustrated in Figure 11 are needed for the description of the warning requirements. For
systems having the ability to estimate the geometry of the roadway, these lines may be defined to follow the
curvature of the roadway.
5.2.4.1.2 Left side closing vehicle warning requirements
5.2.4.1.2.1 General
Referring to Figure 11, a left side closing vehicle warning shall be issued to the subject vehicle driver if a
target vehicle satisfies all of the following conditions:
— the target vehicle is entirely behind line B;
— the target vehicle is entirely to the left of line F;
— any part of the target vehicle is to the right of line G;
— the target vehicle’s estimated time to collision is less than or equal to the value given in Table 4.
Table 4 — Closing vehicle warning time to collision by target vehicle closing speed classification
Maximum target vehicle clos-
Time to collision
ing speed for full performance
Type
m/s s
SAV 10 2,5
MAV 15 3,0
FAV 20 3,5
For target vehicles in the left rear zone behind line A, a left side closing vehicle warning shall not be issued if
all target vehicles have estimated times to collision of 7,5 s or more.
For target vehicles located on or beyond line A, a left side closing vehicle warning shall not be issued if either
of the following conditions is true:
— the target vehicle is entirely in front of line N;
— no part of the target vehicle is located in the area between lines E and H.
5.2.4.1.2.2 Optional left side closing vehicle warnings requirements for road curvature
If LCDAS is designed to cover road curvature situations, the following requirements shall be fulfilled.
Referring to Figure 11, a left side closing vehicle warning should be issued to the subject vehicle driver if a
target vehicle satisfies all of the following conditions:
— the target vehicle is entirely behind line B;
— the target vehicle is entirely to the left of line F;
— any part of the target vehicle is to the right of line G;
— the target vehicle’s estimated time to collision is less than or equal to the value given in Table 5.

Table 5 — Closing vehicle warning time to collision by target vehicle closing speed classification for
road curvature
Maximum target vehicle clos-
Time to collision
ing speed for full performance
Type
m/s s
A 10 2,5
B 15 3,0
C 20 3,5
For target vehicles in the left rear zone behind line A, a left side closing vehicle warning should not be issued
if all target vehicles have estimated times to collision of 7,5 s or more.
For target vehicles located on or beyond line A, a left side closing vehicle warning should not be issued if
either of the following conditions is true:
— the target vehicle is entirely in front of of line N;
— no part of the target vehicle is located in the area between lines E and H.
5.2.4.1.3 Right side closing vehicle warning requirement
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