Field evaluation of unlighted overhead guide signs using older drivers : final report, August 2003.

Zwahlen, Helmut T.; Russ, Andrew; Vatan, Sahika · 2003 · ROSA P / Ohio Research Institute for Transportation and the Environment. Human Factors and Ergonomics Laboratory

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Summary

This study addresses the viability of replacing illuminated overhead guide signs with unlighted signs utilizing high-performance retroreflective sheeting materials, specifically for older drivers. The research was motivated by the availability of new microprismatic materials (ASTM Types VII, VIII, and IX) that offer higher retroreflectivity than traditional engineer-grade or high-intensity sheeting. Transitioning to unlighted signs could reduce energy consumption, eliminate luminaire maintenance costs, and decrease worker and traffic hazards associated with lighting infrastructure. The study aimed to determine if these new materials provide adequate visibility and legibility for older drivers, who have greater visual needs, compared to existing illuminated practices in Ohio. The researchers conducted a field evaluation on US Route 30 near Mansfield, Ohio, involving twenty older drivers aged 63 to 81 with corrected visual acuity ranging from 20/20 to 20/29. Participants evaluated six sign material combinations under nighttime conditions using low-beam headlights. The tested combinations included unlighted beaded Type III on Type III, lighted beaded Type III on Type III (representing existing practice), Type VIII on microprismatic Type III, Type IX on beaded Type III, Type IX on Type IX, and Type VII on beaded Type III. Evaluators rode in a 2002 Dodge Caravan, approaching signs from both left and right lanes. Data collection involved subjective assessments via questionnaires on visibility, legibility, and appearance after each sign group, as well as an exit interview. The study also included objective measurements of observation angles, retroreflectivity, and photometric luminance, alongside legibility analysis using Ohio University’s LEGI software. The results indicated that unlighted signs using advanced materials significantly outperformed the existing illuminated standard. The Type IX on Type IX and Type VII on beaded Type III combinations received the highest ratings for legibility and visibility. In the exit interview, 80% of evaluators deemed Type IX on Type IX acceptable for nighttime use, and 65% accepted Type VII on beaded Type III. In contrast, the lighted beaded Type III on Type III sign, representing current Ohio practice, was deemed acceptable by only 40–45% of evaluators. The Type VIII on microprismatic Type III sign performed comparably to the lighted group in exit interviews but scored lower on detailed evaluation forms. The unlighted beaded Type III on Type III combination had the worst performance overall. The study concludes that switching from lighted signs to unlighted signs using Type VII on beaded Type III or Type IX on Type IX materials represents an actual improvement for older drivers. This transition offers enhanced legibility and visibility while providing economic and safety benefits through reduced electricity usage and maintenance. The authors recommend using Type IX on Type IX signs for short-distance applications to better accommodate the visual needs of older drivers, superseding previous suggestions of Type IX on beaded Type III.

Key finding

Type IX on Type IX and Type VII on beaded Type III unlighted signs were rated significantly higher for legibility and visibility by older drivers than the existing lighted beaded Type III signs, with 80% and 65% acceptance rates respectively compared to 40-45% for the lighted standard.

Methodology

field_study

Sample size: 20

Provenance

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

Topics

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• sign visibility legibility
• signage environment
• vehicle conspicuity
• roadway lighting effects
• visibility analysis litigation