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Presentation Date



Civil and Construction Engineering


Accident prediction models, popularly known as safety performance functions (SPFs) play an important role in roadway safety analyses and evaluation processes. The 2010 Highway Safety Manual (HSM) provides a number of SPFs that can be used locally after calibration to reflect local conditions. However, most of these SPFs focus on intersections and roadway segments. A limited number of studies have developed SPFs for interchanges and especially on-ramps and their related sections such as ramp segments and point of freeway entry. This study was an effort to develop Michigan-specific SPFs for urban partial cloverleaf (parclo) on-ramp loops at freeway entry. A number of factors associated with crash frequency on these facilities were examined, and the SPFs developed for urban partial cloverleaf loops, are presented.