Over the past decade, several fatal truck-related crashes have occurred on the elevated freeway over the Atchafalaya Basin segment of Interstate 10 in southern Louisiana. In an attempt to reduce the crash rates, the Louisiana Department of Transportation and Development has implemented two policies to regulate the truck traffic on this rural section of freeway. These policies restrict truck traffic to the right lane and reduce the maximum truck speed limit to 55 mph while maintaining passenger car speed limits at 60 mph. To investigate potential relationships between compliance with these policies and crash rates, traffic and crash data were collected for the segment while the policies were in force. Relationships between hourly observations of crash rates and compliance rates were sought at the .05 significance level with multiple linear regression. The traffic characteristics that might affect such a relationship were also incorporated into the regression models. These characteristics included difference between truck and car speeds, speed variance, truck volume, and lane occupancy. The regression models were performed with SAS software. Confidence intervals on the means of the explanatory variables were constructed to understand the variability in the values of the traffic characteristics over different days of the data collection period. The results showed that violation of the lane restriction and truck speed limits, truck speed variance, differences between car and truck mean speeds, and lane occupancy were positively correlated with crash rates. The findings suggested that prohibiting trucks from traveling in the left lane and setting a truck speed limit of 55 mph and a car speed limit of 60 mph on a four-lane elevated rural freeway can offer traffic safety benefits.
