Challenge

Crash frequency consistently ranked high on the section of Interstate 10 that runs through central Phoenix, due to traffic volumes in conjunction with substantial weaving associated with two system interchanges, a continuous HOV lane access and a tunnel. Identifying causal factors and assessing the potential impact of improvements was difficult due to the complexity of corridor operations and roadway geometry. Existing tools and methods were insufficient to perform a quantitative safety performance evaluation.

Solution

Our team applied AASHTO Highway Safety Manual (HSM) freeway crash predictive methods to quantitatively assess safety performance, which involved identifying sites with a high potential for crash reduction, identifying and assessing potential countermeasures, and analyzing the benefit/cost of improvement projects. We conducted a detailed diagnostic assessment of safety performance within the freeway corridor and developed calibration factors so that the HSM methodology better reflected local conditions in the Phoenix metro area.