The goal of the study was to determine local calibration factors (LCFs) to adjust predicted motor vehicle traffic crashes for the Maryland-specific application of the Highway Safety Manual (HSM). Since HSM predictive models were developed using data from states other than Maryland, the predictive models should be calibrated. LCFs for all 18 facility types were calculated using Maryland data. After data collection and compilation, samples were drawn based on 90% confidence level, which increased the overall sample size. After the comparison between HSM default crash proportion and Maryland specific data, the use of the Maryland data was suggested. In general, LCFs for all facilities were less than 1.0, implying Maryland had fewer crashes than predicted crashes estimated by HSM crash prediction methodology. Especially, LCFs for intersections were extremely low. Due to potential issues with unreported minor and property damage only crashes, the authors recommend using LCFs for fatal and injuries crashes where available. The report concludes with a discussion on data limitation, thoughts about HSM sampling requirement, and suggestions for future research. It should be noted that this study only considered roadways maintained by SHA and Baltimore City was not part of this study. (Author/publisher)
Abstract