Developing Louisiana Crash Reduction Factors [Final Report]

2013PDFTech ReportFHWA/LA.12/506LTRC Project Number: 08-3SSState Project Number: 30000149Traffic crashesCountermeasuresMultilane highwaysFreewaysRoad markingsStripingHighway safetyCrash dataLouisianaLouisiana. Dept. of Transportation and DevelopmentSun, XiaoduanDas, SubasishUniversity of Louisiana at Lafayette. Department of Civil and Environmental EngineeringUnited States. Federal Highway AdministrationUS Transportation CollectionThe Louisiana Strategic Highway Safety Plan is to reach the goal of Destination Zero Death on Louisiana roadways. This tall order calls for implementing all feasible crash countermeasures. A great number of crash countermeasures have been identified by various representative documents; however, crash countermeasures unique to Louisiana have not been thoroughly evaluated before. After reviewing and documenting crash countermeasures as well as their crash modification factors (CMF), the research team developed two CMFs that are unique in Louisiana. The first CMF is for converting four-lane urban undivided roadway to five-lane roadway. Undivided multilane roadways have consistently exhibited low safety performance, particularly in urban or suburban areas where roadside development is relatively intense. Although the five-lane roadway is no longer an acceptable roadway type for new construction in Louisiana, the impressive crash reductions on several urban roadway segments clearly demonstrate it as a feasible solution under financial constrained conditions. Based on the statistical analysis with six years of crash data (three years before and three years after excluding the project implementation year), the CMFs for all roadways are estimated to be less than 0.6 with a standard deviation less than 0.07. The second CMF developed is for raised pavement markers and striping. Raised pavement markers (RPM) are intended as safety devices on roadways. Intuitively convinced by its safety benefits, Louisiana Department of Transportation and Development (DOTD) has been using RPM for many years on all freeways in the state. This project evaluates the safety benefit of RPM along with pavement striping on freeways with nine years of data. The analysis results from three analysis methods indicate that RPM has significant benefit in reducing nighttime crashes on rural freeways and there are no safety benefits on urban freeways.93