Paper Details

TRB 91st Annual Meeting (January 22-26, 2012)

Event Number:	648
Event Title:	Highway Safety Performance
Event Date:	Jan 24 2012 7:30PM- 9:30PM
Event Location:	Marriott, Salon 2
Event Description:
Event Agenda:

Effects of State-Specific Safety Performance Functions, AADT Estimations, and Overdispersion Parameters on Crash Predictions Using SafetyAnalyst (12-4332)

SafetyAnalyst performs network screening using empirical Bayes approach which requires safety performance functions (SPFs) in addition to roadway characteristics, traffic, and crash data. Simple SPFs (i.e. crashes are predicted as a function of traffic alone) are used by SafetyAnalyst. These simple SPFs were generated using CA, MN, NC, OH, and WA data. Within the software, these national default SPFs are calibrated to represent the agency’s data. How well these calibrated default SPFs fit another state’s data is a question yet to be answered. This research aims at comparing the fit of Georgia specific SPFs and the national default SPFs calibrated to Georgia data. As hypothesized, it was found that state specific SPFs fit the data well, however, the accuracy of traffic data significantly affected the fit of SPFs. SPFs developed using longer segments and with actual traffic data have lower overdispersion parameter with minimal amount of unaccountable dispersion than the SPFs developed using segments with both actual and estimated traffic data.

Authors
     Alluri, Priyanka , Florida International University
     Ogle, Jennifer Harper, Clemson University