FINDINGS OF CRASH ANALYSES RELATED TO RAISED MEDIANS AND DRIVEWAY DENSITIES

Research across the United States has found that access management techniques, such as raised medians and low access point densities typically provide for safer roads with lower crash rates than roads without access management. As the Texas Department of Transportation (TxDOT) recently continued making progress toward developing and implementing an access management program, TxDOT desired to identify crash rates specific to Texas. The research team studied 11 corridors to determine relationships between crash rates and access point (driveways and public street intersections) densities, as well as the presence of raised medians or two-way-left-turn-lanes (TWLTLs). Some corridors had two or more distinct segments, each with varying access point densities. Researchers obtained crash history and traffic volumes for each of the corridor segments. The Texas Department of Public Safety (DPS) provided accident reports for each of the corridors that are state-maintained roads. For the other corridors in Texas, city police departments provided crash information. The Oklahoma Department of Transportation (ODOT) provided crash information for the Tulsa corridor. This paper describes the crash analysis performed along 10 case study locations in Texas and one in Oklahoma. The analysis provides a safety estimate on corridors after installation of access management techniques, comparisons of corridors with and without raised medians, and varying access point densities. Researchers investigated three locations where a raised median was installed to replace TWLTLs and two locations where raised medians were added to undivided roads. The case study analyses indicate that crash rates increase as access point densities increase and that crash severity tends to be worse on corridors that do not have raised medians, compared to corridors with raised medians.