The Effect of Design and Placement of Work-Zone Warning Signs on Driver Speed Compliance: A Simulator-Based Study

Abstract

OCCUPATIONAL APPLICATIONS In this work, simulated driving was used to test how characteristics of dynamic message signs impact driver behavior when entering designated work zones. Driver compliance with posted speed limits was measured in response to signs that differed in terms of placement distance and type of sign design. Signs should be placed farther ahead of the work zone to enhance speed compliance. Such compliance can also be enhanced by using concise sign content. TECHNICAL ABSTRACT Background and Rationale: In recent years, the number of occupational fatalities occurring as a result of workers being struck by vehicles while on the job has remained high. Fatalities are especially apparent at road construction sites, where nearly half of the fatal occupational injuries were classified as a worker being struck by a moving vehicle, highlighting the need for research to identify techniques to reduce the incidence of injury in future years. Purpose: This project investigated how the characteristics of a dynamic message sign can impact driver compliance with posted information in work-zone settings, specifically signs indicating speed reduction. Methods: Driving simulation was used to assess the effects of three placement distances (305, 457, and 610 m before the work zone) and four sign designs (differing in whether the sign was static versus dynamic and the amount of information presented). The study was completed by 39 participants, during which driving speed and compliance with speed change were recorded. Results: Placement of the speed-reduction signs impacted driver behavior, with greater placement distances being associated with higher speed reduction and compliance rates. Speed reduction was also significantly impacted by sign design, with the largest speed reduction apparent with signs that are static or with dynamic signs that presented one complete statement per display frame. Conclusions: To achieve greater driver compliance with speed limits within work zones, greater sign placement distance is preferred. The content of dynamic message sign needs to be engineered to increase driver compliance by presenting direct, relevant information in concise and complete phrases.