Semester of Graduation

Spring 2023


Master of Science in Civil Engineering (MSCE)


Department of Civil and Environmental Engineering

Document Type



Lack of visibility is one of the main challenges that significantly impact drivers’ ability to safely perform driving tasks at night especially at unsignalized intersections. Several prior studies indicated that lighting enhances nighttime traffic safety. Nevertheless, lighting is not mandatory at unsignalized intersections in many states including Louisiana. This study aimed to investigate if lack of lighting is a contributing factor that affects traffic safety at unsignalized intersections in Louisiana. In addition, this study strived to identify current lighting policies adopted by other states, examine if there are any low-cost countermeasures implemented by other states to improve nighttime visibility, and evaluate the impact of different lighting conditions on drivers’ behavior/safety.

To achieve these objectives, three different approaches were employed including crash data analysis, national survey among U.S. departments of transportation (DOT) professionals, and driving simulator experiment. The crash data analysis revealed that failure to yield was the prevalent contributing factor of nighttime crashes at roundabouts and stop-controlled intersections. It was also found that the interaction effect between failure to yield and lack of lighting was a significant factor affecting the number of injuries/fatalities in nighttime crashes. One possible explanation is that drivers may have failed to notice the intersections due to absence of lighting and that could have led to nighttime crash occurrence.

Regarding the survey study, a total of 32 states responded to the survey (64% response rate). The survey indicated that 72% of the states do not require lighting at stop-controlled intersections, whereas 67% of the states require lighting at roundabouts. Several states reported utilizing low-cost countermeasures to improve safety during nighttime including reflective pavement markings/markers, larger, and double signs, among others. In the driving simulator experiment, participants drove through several stop-controlled intersections and roundabouts during daytime, nighttime without lighting, with partial and with full lighting. Several surrogate safety measures including time-to-collision (TTC), post-encroachment-time (PET), and speed were gathered. The results indicated that lighting improves drivers’ safety at stop-controlled intersections by providing 23% increase in TTC/PET and 4% reduction in speed.

According to the findings of this study, lighting improves drivers’ safety/behavior. Therefore, it is recommended to provide full lighting at roundabouts and to provide lighting at stop-controlled intersections based on traffic safety analysis. However, if lighting installation is impractical due to limited funds or right-of-way restrictions, then it is recommended to install low-cost countermeasures as reported by DOT professionals.



Committee Chair

Hassan, Hany



Available for download on Friday, April 04, 2025