Use of Graphics and Symbols on Dynamic Message Signs: Technical Report

Ullman, Brooke R.; Trout, Nada D.; Dudek, Conrad L. · 2009 · ROSA P / Texas Transportation Institute

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Summary

This technical report addresses the evolving capability of Dynamic Message Signs (DMSs) to display graphics and symbols, moving beyond traditional alphanumeric text. The research was motivated by the limitations of standard three-line text messages, which often fail to convey complex traffic information—such as lane closures at major interchanges or incident severity—within the brief viewing times available to drivers. The study aimed to determine how graphic displays could improve driver comprehension, reduce information loading issues, and assist non-native English speakers in understanding roadway conditions. The researchers conducted a multi-phase evaluation involving focus groups and two levels of human factors laboratory studies. The focus groups gathered initial feedback on design concepts for various scenarios, including incidents, work zones, High-Occupancy Vehicle (HOV) lane usage, and truck routing. The Level 1 laboratory study evaluated specific design elements, such as accident symbols, arrow configurations, and graphical route information panels (GRIPs), assessing driver interpretation and preference. The Level 2 laboratory study compared graphic versus text messages directly, measuring comprehension rates, viewing times, and route decision-making among both English and Spanish-speaking participants. Key findings indicate that graphic displays offer significant advantages over text-only messages. Graphics improved drivers' ability to identify available lanes in complex problem areas and effectively illustrated unusual operational scenarios, such as adjacent toll lanes or HOV lane openings. Crucially, the use of symbols significantly improved comprehension levels for non-native language speakers, such as those whose primary language is Spanish, and reduced the viewing time required for understanding. The studies identified specific design recommendations, favoring clear symbols for incident descriptors and graphical representations of roadway geometry over dense text. The significance of this work lies in providing evidence-based guidance for transportation agencies adopting full-matrix DMS technology. The report concludes that graphics can offset the limitations of word messages in high-workload environments by allowing for faster information extraction and broader accessibility. By defining which design elements enhance communication and which should be avoided, the study supports the development of standards for using symbols and graphics to improve freeway safety, operations, and driver decision-making.

Key finding

Graphic displays on Dynamic Message Signs improve lane identification, enhance comprehension for non-native speakers, and reduce viewing time compared to equivalent text messages.

Methodology

lab_experiment

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• signage environment
• sign visibility legibility
• ehmi external hmi