Assessment and Improvement of Motorist Understanding of Traffic Control Devices

Mounce, John M.; Hawkins Jr., H. G.; Womack, Katie N. · 1991 · ROSA P / Texas Transportation Institute. Texas A&M University

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Summary

This interim report documents the first year of a three-year study aimed at assessing and improving motorist comprehension of traffic control devices (TCDs) in Texas. The research was motivated by the increasing complexity of signs, signals, and markings, which has led to driver confusion, potential accidents, and liability issues. Factors contributing to this misunderstanding include an aging driving population, urban congestion, specialized devices for priority facilities, a growing Hispanic driver demographic, and insufficient instruction in driver education programs. The study’s objective is to conduct a statistically valid survey of Texas motorists to identify devices that are poorly understood and to recommend improvements through design revisions or public education. The methodology involved a comprehensive literature review and a multi-stage selection process to identify critical TCDs for testing. Researchers analyzed previous studies to identify devices with historically poor comprehension scores. They then canvassed state transportation personnel and polled 49 transportation professionals to rank devices based on importance, consequence of misunderstanding, frequency of use, and prior research findings. This process narrowed the field from the extensive Texas Manual on Uniform Traffic Control Devices to 60 devices for a pre-test survey, which was further refined to 46 devices for the pilot and final surveys. The survey instrument utilized video presentations showing in-context and close-up images of devices, followed by multiple-choice questions designed to detect specific misunderstandings. The study conducted a pre-test survey with 38 drivers in Bryan/College Station and a pilot survey with 165 volunteers at the 1991 Houston Auto Show. The pilot survey results identified several devices with low comprehension rates. For instance, only 20.6% of respondents correctly understood "Two-Way Left Turn Markings," while 30.9% correctly identified "GROOVED PAVEMENT AHEAD" and "PROTECTED LEFT ON GREEN." Other poorly understood devices included the "Two-Way Left Turn Lane" post (37.6%) and "Turn" signs (38.2%). These findings were used to refine the survey instrument for the final phase. The significance of this work lies in its potential to enhance roadway safety and reduce liability by aligning TCD design with driver capabilities. The interim report outlines the plan for the final survey, which targets 2,000 drivers across 12 Texas cities, using quota sampling to ensure representation by gender, age, and ethnicity. The ultimate goal is to provide evidence-based recommendations for modifying device standards or enhancing driver training programs to address identified comprehension gaps.

Key finding

The pilot survey of 165 motorists revealed that two-way left turn markings had the lowest comprehension rate at 20.6 percent, while grooved pavement ahead signs were understood correctly by only 30.9 percent of respondents.

Methodology

survey

Sample size: 165

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
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• signaling behavior
• perceptual countermeasures
• emergency work zone conspicuity
• sign visibility legibility