ISO/TR 23049:2018

Road Vehicles - Ergonomic aspects of external visual communication from automated vehicles to other road users

The purpose of this document is to provide guidance for developers of visual external communication systems for automated vehicles (AV), particularly Automated Driving System ? Dedicated Vehicles (ADS-DV), as defined by SAE J3016. The main objective of this document is to propose how ADS-DVs could communicate with other road users via an external communication system. It discusses the interaction between humans and ADS-DVs within roadway environments. Recommendations for the type of external visual communication messaging are presented along with the supporting methodological rationale. This document does not address functionality elements of the ADS-DV external visual communication system itself. Rather, it serves to propose how the system communicates to human users such that it can be learned and understood by society at large.

Véhicules routiers — Aspects ergonomiques de la communication visuelle exterieure du véhicule automatisé aux autres utilisateurs de la route

General Information

• Status: Published
• Publication Date: 12-Sep-2018
• ICS: 03.220.20 - Road transport
• ICS: 43.020 - Road vehicles in general
• Technical Committee: ISO/TC 22/SC 39 - Ergonomics
• Drafting Committee: ISO/TC 22/SC 39/WG 8 - TICS on-board-MMI
• Current Stage: 6060 - International Standard published
• Start Date: 13-Sep-2018
• Due Date: 23-Apr-2019
• Completion Date: 23-Apr-2019

Overview - ISO/TR 23049:2018 (External visual communication for automated vehicles)

ISO/TR 23049:2018 provides ergonomic guidance for designers and developers of external visual communication on automated vehicles, with a particular focus on Automated Driving System - Dedicated Vehicles (ADS‑DV) as defined in SAE J3016. The Technical Report addresses how ADS‑DVs could visually communicate with other road users (pedestrians, cyclists, other drivers) to improve human‑vehicle interaction, learnability and public acceptance. It is guidance rather than a prescriptive performance standard and does not specify system functionality or technical implementation.

Key topics and recommendations

• Purpose & scope
  • Guidance for visual, external messaging so road users can learn and understand AV behaviour.
  • Emphasizes consistency and societal learnability across the industry.
• Types of information to communicate
  • Vehicle state: speed, acceleration/deceleration, idle (e.g., traditional signals like brake lights).
  • Driving mode: whether the vehicle is under automation (ADS‑DV).
  • Perception: what the vehicle “sees” in the environment (e.g., detected pedestrians or obstacles).
  • Recognition & acknowledgment: whether the vehicle recognizes specific road features or users.
  • Belief state: the vehicle’s understanding or expectations (e.g., intent regarding right‑of‑way).
  • Intent: planned manoeuvres (similar to turn signals but potentially richer).
  • Guidance: telling others what to do (not recommended currently due to safety and legal risks).
• Format & human factors
  • Focus on visual modality because traffic interaction is primarily visual.
  • Limit number of signals, ensure distinctness and salience, avoid distraction and ambiguity.
  • Consider directional targeting, cultural/local norms, and crowded environments.

Practical applications and users

• Who uses this TR
  • OEMs and AV system designers creating external displays and signalling concepts.
  • Human factors and UX teams working on human‑vehicle communication.
  • Regulators, policy makers and city planners evaluating AV deployment and signage needs.
  • Road safety researchers assessing behavioral impacts and public acceptance.
• Practical uses
  • Informing concept design for exterior LEDs, displays or light patterns.
  • Developing user studies to validate learnability and comprehension.
  • Aligning industry practices to reduce road‑user confusion and improve traffic safety.

Related standards and context

• References SAE J3016 for ADS‑DV definitions.
• Aligns with policy discussions (e.g., NHTSA) on AV communication and accessibility (audible alerts for low‑speed EVs).
• Intended to support harmonized approaches rather than mandate technical specifications.

Keywords: ISO/TR 23049:2018, external visual communication, automated vehicles, ADS‑DV, ergonomics, human‑vehicle interaction, vehicle intent, visual signalling, vehicle-to-pedestrian.

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 23049
First edition
2018-09
Road Vehicles — Ergonomic aspects of
external visual communication from
automated vehicles to other road users
Véhicules routiers — Aspects ergonomiques de la communication
visuelle exterieure du véhicule automatisé aux autres utilisateurs de
la route
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Introduction .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Background . 1
5 Current road user interactions . 2
6 Potential ADS-DV communication . 2
6.1 General . 2
6.2 Vehicle information . 2
6.2.1 State . 2
6.2.2 Driving mode . 3
6.3 Vehicle “understanding” of the environment . 3
6.3.1 Perception . 3
6.3.2 Recognition and acknowledgment . 3
6.3.3 Belief state . 3
6.4 Guidance . 3
6.5 Intent . 4
7 Format of ADS-DV communication . 4
8 Considerations for ADS-DV communication . 4
9 Acceptance of ADS-DVs by the public . 5
Bibliography . 7
Introduction
The need for external communication was highlighted in the National Highway Traffic Safety
Administration’s (NHTSA) 2017 automated vehicle policy: “New complexity is introduced to this
interaction as ADSs take on driving functions, in part because in some cases the vehicle must be
capable of accurately conveying information to the human driver regarding intentions and vehicle
performance”.
This document focuses on the various ways to enhance traffic scenarios by suggesting communication
from Automated Driving Systems (ADS-DV)s [16]. While communication may involve many modalities
(visual, speech, audio signals, haptics, etc.) and combinations thereof, this document mainly focuses on
the visual modality, since interaction with vehicles is primarily a visual task [13].
As AV systems enter the market, road users need to understand how to safely interact with these vehicles.
This is particularly important when situations occur such as uncertainty of right-of-way involving road
users of all types including AVs, pedestrians, bicyclists, drivers, and passengers. Although there is still
some discussion about the need to provide external communication, it is important to start working
on this concept. Within the minimum sound requirements for hybrid and electric vehicles (2016), the
NHTSA requires non-internal combustion vehicles add an audible alert so that pedestrians with visual
impairment can hear these vehicles at low speeds, full compliance by September 2019. Since any other
audible signals would conflict with this regulated signal, visual signalling is recommended. Since the
implementation of supplemental visual signalling on ADS-DVs may help other road users navigate
traffic scenarios more easily, there is a need to investigate standardizing signals if they are to be used.
Consistency across the automotive industry is needed to minimize potential road user confusion and
establish societal trust with respect to ADS-DVs. This includes design considerations made for vehicles
of different types and sizes.
It is recommended that if ADS-DVs have external visual communication systems, the communication
should be standardized across the automotive industry. Learnability of these systems is a main focus,
limiting the number of signals and ensuring they are distinct and salient yet not distractive, with the
aim of their implementation providing a positive impact on societal acceptance and traffic safety.
iv © ISO 2018 – All rights reserved

TECHNICAL REPORT ISO/TR 23049:2018(E)
Road Vehicles — Ergonomic aspects of external visual
communication from automated vehicles to other road
users
1 Scope
The purpose of this document is to provide guidance for developers of visual external communication
systems for automated vehicles (AV), particularly Automated Driving System – Dedicated Vehicles
(ADS-DV), as defined by SAE J3016.
The main objective of this document is to propose how ADS-DVs could communicate with other road
users via an external communication system. It discusses the interaction between humans and ADS-
DVs within roadway environments. Recommendations for the type of external visual communication
messaging are presented along with the supporting methodological rationale.
This document does not address functionality elements of the ADS-DV external visual communication
system itself. Rather, it serves to propose how the system communicates to human users such that it
can be learned and understood by society at large.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Background
As ADS-DVs enter the market, road users will need to interact with them in an effective manner. In
manually-driven vehicles, the effectiveness of interactions are based intrinsically on the rules of the
road that define priorities for given situations. Recent studies have also shown that vehicle behaviour
also determines the behaviour of other road users [ ]. However, at times it is difficult to resolve a
specific situation deterministically. Common situations include conflict with another road user,
uncertainty as to who has the right-of-way, accommodation of other road users, and acts of fairness on
the road. Currently, such situations are sometimes resolved by coordination and negotiation between
two or more humans such as interactions between driver-pedestrian, driver-driver, and driver-cyclist.
Since a human driver may not be in an ADS-DV or a person may be in the vehicle but not actively
controlling it, effective human-to-human interactions likely will not be feasible and a substitute may be
needed. The vehicle’s behaviour will be programmed or will be a response to changing circumstances,
which may deviate from what people expect in normal human-human interaction. Therefore, a new
way of communication may need to replace these traditional human-to-human communications by
communicating the ADS-DV’s current or planned behaviour with other road users. Such communication
could enable other road users to make more judicious decisions and enable better public acceptance
of ADS-DVs. Studies are currently investigating the needs and benefits of visual communication of
automated vehicles to surrounding traffic and other road users.
5 Current road user interactions
Currently, vehicular road communication concerns vehicle state, intent and warnings, and several
methods of communication are utilized. Vehicles have dedicated signals that have conventional and
sometimes regulated meanings; these signals can provide state information (brake light, reverse horn
in trucks), intent information (turn signal to indicate intended departure from current lane), and general
warnings (honking, hazard light). These signals are not sent directionally to a specific road user, but all
recipients are expected to respond by taking a suitable action or, at least, by taking notice. Additional
means of communication are informal vehicle signals, such as blinking the headlights or tapping on the
brakes, but the meaning of these messages is ambiguous and depends on local and cultural norms.
A driver can also communicate by taking dynamic actions such as moving into a conflict space, cutting
into the gap between vehicles, or creeping forward onto a busy crosswalk. Finally, there are explicit
communication forms such as hand signals, head movements, torso movements, as well as implicit
communication such as eye contact [ ]. What is unique about these human-to-human communications
is that they are usually directional and intended for specific road users. Currently, such human-to-
human communication is used to resolve difficult situations; for example, in Germany, the rules
of the road mandate this kind of communication when road signs and traffic rules are not enough.
While human-to-human communication is often effective in resolving traffic situations, it can also be
misinterpreted or misused, leading to complications.
The most certain means of communication from a driver is vehicle motion as this indicates what the
driver is actually doing as well as the driver’s intent. For instance, at a stop if a driver takes their foot
off the brake in an automatic-transmission vehicle, the car begins to inch forward, communicating both
that the vehicle is starting to go as well as the driver expects to go next. There is a strong correlation
between vehicle movement and communications, and any new signalling scheme will need to have that
in mind. When vehicle motion state is likely to change imminently, secondary cues could be necessary
to better anticipate the future vehicle behaviour. Brake lights fulfil these tasks as well as eye contact
between pedestrians or side traffic with the driver of the car concerned. ADS-DVs should enable this
information exchange.
6 Potential ADS-DV communication
6.1 General
A traditional vehicle and an ADS-DV can communicate in several methods. The following outline
describes these, considering conveyable information and relevance to road users.
6.2 Vehicle information
6.2.1 State
Vehicle state encompasses speed, rate of acceleration, deceleration, idle, etc. Vehicle state has
traditionally been communicated implicitly through observable behaviours without the requirement
of extra displays; however, this information can be signalled explicitly by multiple modalities. One
acoustic modality example is the tone and beeps used by trucks when backing up or the additional
sounds generated by EVs in lower speed conditions. A visual example involves brake lights indicating
deceleration. In their evaluation of vehicle-to-pedestrian communication displays for AVs, Clamann,
Aubert, and Cummings [ ] utilized a dedicated visual display on a grid which showed vehicle speed
as white text on a black background. The benefits and potential consequences of such explicit signal
concepts for vehicle state would need further exploration.
2 © ISO 2018 – All rights reserved

6.2.2 Driving mode
While driving mode can be considered a division of vehicle state, there is also a distinction. Outside of
common driving behaviours, communicating driving mode is meant to convey different information to
other road users and may have a different impact on behaviour. Driving mode communication would
indicate whether the vehicle is operated by automation. An ADS-DV can provide information to other
road users to alert them to the fact the vehicle is an ADS-operated vehicle. There is much debate as to
whether there is a need to indicate this mode information, considering both the concern that certain
road users may wish to “game” such a vehicle or take advantage of it as well as the benefit of enhancing
its conspicuity.
6.3 Vehicle “understanding” of the environment
6.3.1 Perception
A signalling mechanism that provides information to the “world” about what the vehicle sees can be
introduced, though the effectiveness of these mechanisms remains unclear. For example, an ADS-DV
that is approaching a crosswalk can display to the car behind it that there are pedestrians crossing the
road (something that the vehicle behind cannot “see”). An ADS-DV that quickly avoids an obstacle can
indicate the reason for the abrupt manoeuvre to the car behind it.
6.3.2 Recognition and acknowledgment
Another type of information that an ADS-DV can broadcast is its recognition of the scene. For example,
it can indicate whether it recognizes the crosswalk and stop line and whether it r
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