Impact of traffic citations to reduce truck crashes on challenging roadway geometry.

Wyoming's Interstate 80 has one of the highest truck crash rates in the United States. This is due to a variety of reasons, including high percentage of truck traffic, adverse weather conditions and mountainous terrain. These factors have caused the Wyoming Highway Patrol (WHP) to spend extensive resources on inspecting commercial vehicles and enforcement of traffic laws in this corridor. This study estimated the correlation between traffic citations and truck crashes. In addition, the paper evaluated the increased risk of truck crashes in adverse weather and road conditions. The explanatory variables included geometric features, weather condition, traffic volume and types of citations. This research concluded that speeding related citations and truck crashes are negatively correlated, and the risk of truck crashes is significantly higher when weather is not clear, and the road is not dry.

Truck safety evaluation on Wyoming mountain passes.

The Manual on Uniform Traffic Control Devices (MUTCD) for Streets and Highways recommends hill signs be placed in advance of downgrade descent of mountain passes. Mountain passes increase the risk of a runaway, or out of control trucks and so the advance warning signs inform the driver to take special precautions such as reducing speed or using lower gears during the descent. The Wyoming Department of Transportation has installed steep grade advance warning systems on Wyoming mountain passes. However, concerns for out of control trucks on the mountain passes persist. The objective of this study is to evaluate the safety effectiveness of steep grade advance warning signs for trucks on Wyoming mountain passes. The safety evaluation was carried out by implementing a zero-inflated negative binomial modeling technique for predicting truck crashes on mountain passes. The outcome was two models that showed the risk of runaway truck accidents were high at locations where either the grades were steep and long or the grades were long with multiple vertical curves. The analysis showed the current advance warning systems were not significantly impacting truck crash risks at the high risk locations. The study, therefore, recommends some improvements to the current advanced warning signs or implementing an improved Federal Highway Administration Grade Severity Rating System based warning system that will significantly improve truck safety at the hazardous locations. The study informs policy makers on the safety issues on Wyoming Mountain passes with regards to runaway trucks and makes recommendations for reducing the risk of runaway truck crashes on mountain passes.