The American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) has become a key safety management and evaluation toolbox for state and local highway agencies, metropolitan planning organizations, planning, safety, design, and operations communities. Current HSM tools include predictive methods for a wide variety of highway facility types and site conditions. The current methods account for traffic volumes and other roadway characteristics but not for vehicle mix or distribution of vehicle types.
Recent studies suggest that truck traffic adversely impacts roadway safety performance. These studies indicate that the consideration of vehicle mix would improve predictive methods for crash frequency and severity. Improved methods will result in better use of the limited funds and resources available for improving the safety of the highway system and support performance-based approaches.
The objectives of this research are to (1) develop and validate a statistically valid predictive methodology to quantify the effect of vehicle mix on crash frequency and severity for various facility types; and (2) develop a spreadsheet tool for practitioners to quantify the effect of vehicle mix on safety performance across the range of highway activities including planning, design, operations, and safety management.