ISO/PAS 23735:2025

Overview

ISO/PAS 23735:2025 - "Road vehicles - Ergonomic design guidance for external visual communication from automated vehicles to other road users" provides human-factors guidance for designing external visual communication on single‑mode L4/L5 automated driving system‑dedicated vehicles (ADS‑DVs). The Publicly Available Specification covers passenger cars, SUVs, light trucks, heavy trucks and buses (and their derivatives) operating across multiple domains (open roads, motorways, urban environments, geo‑fenced lanes, ports, terminals and confined areas). The document emphasizes ergonomics, accessibility and the need to make ADS‑DVs recognizably automated while addressing diverse road users (pedestrians, cyclists, motorcyclists, drivers, elderly people, children and people with disabilities).

Key topics and technical focus

ISO/PAS 23735 does not set numeric mandates but gives structured design guidance across these technical areas:

• Framework for interaction between ADS‑DVs and other road users: encounters, interactions and conflict situations.
• Communication channels: explicit vs implicit signalling and how visual signals integrate with natural vehicle motion and other cues.
• Expectation management: how different road users perceive, comprehend and respond to external visual messages.
• Developing a communication language: message content, protocols, media allocation, learnability and addressability.
• Visual attributes and implementation: presentation style, message location on the vehicle, viewing angles, colour, brightness, and coordination with vehicle motion and existing vehicle signals.
• Integration and evaluation: choreography with existing systems, human‑factors testing and methods for evaluating effectiveness.
• Accessibility, demographic and cultural considerations: design for age differences, disabilities and regional expectations.
• Supporting materials: informative Annex A (use cases needing communication) and Annex B (multiple resource theory).

Practical applications

ISO/PAS 23735 is practical guidance for:

• Designing external light displays, pictograms and dynamic message surfaces on AVs.
• Defining human‑centred UX for AV fleet deployments in urban, motorway and confined domains.
• Creating test protocols and validation plans for vehicle–road‑user interactions.
• Informing procurement, deployment policies and signage integration for dedicated automated vehicle zones.

Who should use this standard

• Automotive OEMs and AV system integrators
• Human factors / ergonomics and UX designers
• Vehicle lighting and display engineers
• Regulators, transport planners and fleet operators
• Researchers and test houses evaluating AV road‑user communication

Related standards

• SAE J3016 (definition of L4/L5 ADS terminology) - referenced in the scope
• AVAS concepts and vehicle lighting/signal standards (for multimodal integration)

Keywords: ISO/PAS 23735, external visual communication, automated vehicles, ADS‑DV, L4, L5, ergonomic design, road users, visual signals, vehicle UX.