Public Roads: A Journal of Highway Research and Development, Vol. 40 No. 2

Mast, Truman M.; Ballas, James A.; Peters, Joseph I.; Leifer, Joseph C.; Knepp, Anthony J.; Tseng, Ming T.; Jones, J. Sterling; Tignor, Samuel; Cron, Frederick W. · 1976 · ROSA P / United States. Government Printing Office

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Summary

This paper introduces the In-vehicle Sign Simulation (ISS) method, a research technique developed by the Federal Highway Administration (FHWA) to study motorist responses to highway information systems. The method addresses the limitations of existing research approaches, which were restricted to either artificial laboratory conditions or poorly controlled field environments. The ISS method bridges this gap by providing the rigorous experimental control of a laboratory with the realism of actual driving on highways open to normal traffic. The methodology utilizes a specially instrumented automobile, such as a 1970 Chrysler Imperial, equipped to measure driver responses to visual and auditory stimuli. Experimental signs are projected onto a screen on the windshield, while simulated radio messages are played through the vehicle’s speakers. The system records objective data, including vehicle velocity, steering wheel position, accelerator pedal position, and Information Interpretation Time (IIT). Researchers also employ time-lapse film to analyze lane changes and erratic maneuvers. Subjective data are collected through post-drive questionnaires and direct questioning regarding driver confidence and decision-making processes. The study notes that while the method allows for efficient testing of numerous variables, it is limited by high equipment costs, the need for specialized skills, and a practical sample size limit of approximately 100 subjects. Additionally, aged drivers are excluded due to difficulties adjusting to the in-vehicle displays. The paper details several research applications and findings. The ISS method has been used to evaluate diagrammatic versus conventional guide signs, finding that diagrammatic signs are superior specifically for left exits and major forks, whereas conventional signs may suffice for right exits. It has also assessed changeable message signs, determining that drivers process signs indicating congestion levels faster than those describing incidents or time delays. Furthermore, the method allows for the study of auditory messages, revealing that drivers’ route diversion decisions are influenced by their past experiences with specific incidents described in the messages. The technique enables the simultaneous manipulation of variables such as message modality, function, and placement, allowing researchers to identify interactions that independent testing might miss. The significance of the ISS method lies in its ability to refine highway information systems before full-scale implementation. It serves as an intermediate step between initial laboratory screening and final on-road field evaluations. As transportation systems become more complex with multiple modes and increased information needs, the ISS method provides a vital tool for ensuring that information transmission is efficient and effective. The paper concludes that continued development of such research tools is essential to meet future challenges in surface transportation and to minimize modal conflicts.

Key finding

The In-vehicle Sign Simulation method allows researchers to evaluate driver responses to experimental highway signs with the experimental control of a laboratory while maintaining the realism of actual driving conditions.

Methodology

other

Provenance

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

Topics

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• rail grade crossings
• perceptual countermeasures
• signage environment
• roadway lighting effects
• traffic density

Information type

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• Applied Guidance: countermeasure evaluation
• Methodological Resource: dataset resource, validation psychometrics