Designing warning sign configurations to increase driver attention and improve safety at highway work zones

As cities expand and road networks grow, highway construction and maintenance increase, making work zone safety critical due to high driver and worker fatalities. Driving through work zones is challenging due to speed limit reduction, lane closure, confusing temporary signs, and inattention. To reduce collisions at work zones, warning signs can encourage drivers to reduce speed and drive more cautiously. This study examined how the number of warning signs, the spacing between distance information signs, and the type of signs influence driver behaviour and safety at work zones. A total of 47 drivers' behaviour was observed on a 2.64 km-long highway using a driving simulator. The driving scenarios were created for various warning sign configurations in terms of 3 variables: 1) different numbers of signs (4, 6, or 9), 2) different spacings between the distance information signs (500 or 250 m), and 3) different types of signs (pictorial or text). The driving performance variables including speed and lateral position of vehicle in the lane were collected from the driving simulator. The drivers' responses on their perceived helpfulness, safety, and distraction in different sign configurations were also collected using the survey. The effects of sign configurations, drivers' characteristics and their perception of signs on driver behaviour and safety were evaluated using linear mixed effects models and Cox proportional hazards models. The results of the models show that the warning sign configurations had mixed effects on the mean speed, the lateral distance from the cones within the work zone, and the start time of drivers' speed reduction. The results also show that the drivers are more likely to be aware of the presence of warning signs than the content of signs, and the signs have more direct impacts on the drivers' speed adjustment before the work area than their lateral position adjustment in the work area. Moreover, the results of drivers' survey in relation to their observed behaviours show that driver characteristics and drivers' perception of signs are closely related to their lane change and speed reduction behaviours at the work zone. Findings of this study provide insight into better understanding of the impacts of different warning sign configurations on driver behaviour under each variable and the development of evidence-based variable-specific warning sign design guidelines to mitigate negative effects of the warning sign configurations on safety.