Crash Analyses of Raised Medians and Driveway Density: How Access Management Makes Communities Safer

Implementing raised medians and performing driveway consolidation are proven access management tools that reduce the potential number of conflict points along roadways. The authors of this paper have completed an evaluation of several case studies to estimate the safety impacts of installing raised medians and reducing the number of access points. The research was sponsored by the Texas Department of Transportation (TxDOT). The research team investigated five raised median installation case studies, including three locations where a raised median replaced a two-way left-turn lane (TWLTL) and two locations where a raised median was added to a previously undivided road. The researchers also analyzed crash reports and created matrices that present statistical information about crashes and corresponding driveway densities at different case studies. In some case studies, a corridor consisted solely of high or low driveway density. However, several corridors had two or more consecutive segments, each with a varying driveway density. This paper and presentation describe the analysis of the crash reports and present crash analysis findings that relate to the safety impacts along the case study locations. The paper describes analysis results and statistics related to different crash types before and after median installation, as well as analysis related to driveway density and crashes. The paper also describes identified crash-reporting errors, computation of crash rates, conflict point analysis, and data collection and data reduction methods and experiences. This paper and presentation will be useful to transportation professionals in small and medium-sized communities that are interested in the potential safety impacts of raised medians and driveway consolidation for either new or retrofit corridors along with lessons learned to assist in performing crash analyses.