Minimum Intersection Illumination

20-3SASIO No. DOTLT1000373Numerous prior studies indicated that street lighting improves nighttime traffic safety. However, lighting at unsignalized intersections (e.g., stop-controlled intersections and roundabouts) is not mandatory in some states such as Louisiana. This study aimed to examine whether Louisiana has traffic safety problems due to lack of lighting at its rural and suburban roundabouts and stop-controlled intersections. Underlying this goal, this study set out to (1) record the lessons learned from other states that had implemented partial or full lighting policies or other potentially low-cost countermeasures at their intersections; (2) explore whether the lighting at intersections has a significant impact on the behavior and safety of drivers; and (3) determine the viability of installing lighting at these types of intersections in Louisiana. To achieve these goals, four different approaches were employed: (1) crash data analysis, (2) online national survey among professionals working at the departments of transportation (DOTs) in the US, (3) driving simulator experiment, and (4) cost-benefit analysis

Examining the Impact of Different Street Lighting Schemes on Traffic Safety and Drivers’ Behaviors at Unsignalized Intersections

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

Developing Notification and Enforcement Systems to Communicate and Administer Bridge Load Postings

State and local law enforcement agencies in the US strive to enforce weight restrictions on trucks and heavy vehicles travelling on public roads as a matter of public safety and as a way of safeguarding vital transportation infrastructure. This research aimed to identify plausible notification systems that can effectively communicate bridge load postings to dispatchers and drivers, investigate and suggest possible approaches to communicate potential detour routes, and identify corresponding enforcement methods required to successfully administer bridge load postings. This report discusses the current practices of bridge load posting notification and enforcement systems. Also, it presents an overview of the existing conditions of intelligent Transportation systems (ITS) in Louisiana that included: Traffic Management Centers (TMCs), Motorist Assistance Patrol (MAP) service, ITS devices, and technologies. A national survey was also conduct targeting US Departments of Transportation (DOTs) professionals and law enforcement agencies in USA to obtain their feedback and insights regarding the current bridge load posting notification and enforcement procedures/systems, its limitations and required modifications at their States. The results of this research suggest that improving the notification methods alone is not enough to ensure public compliance with posted weight limit on bridges, therefore, the enforcement methods need to be improved as well to enhance drivers’ compliance and to prolong the lifespan of bridges. The report concluded by providing recommendations that can improve the notification and enforcement systems to effectively communicate and administer bridge load posting