Abstract
In this study, crash modification factors (CMFs) for the effect of signalization at intersections in Florida were estimated. This paper applies the empirical Bayes method to develop CMFs for KABCO, KABC, and rear-end crashes by using several safety performance functions (SPFs) from various jurisdictions, adjusted by calibration factors. [In the KABCO scale, K = fatal (killed), A = incapacitating injury, B = nonincapacitating injury, C = possible injury, and O = property damage only.] Florida and Ohio data were used to develop these SPFs. Also, the SPFs suggested in the Highway Safety Manual were used to calculate CMFs. Through development of the SPFs and comparison of SPFs from different states, the study concluded that it might not be suitable to apply SPFs from other states without thorough examination. The CMF was 0.785 for KABCO with the SPF from Florida, significantly smaller than 1; this result indicated that the signalization at intersections resulted in fewer total crashes. But when the SPFs from Ohio and the Highway Safety Manual were applied, higher CMFs of 1.06 and 1.07 were obtained, respectively. These were significantly larger than 1; this result shows that the signalization brings about more total crashes. CMFs for KABC and rear-end crashes are discussed in this paper as well. The major finding of this study is that the CMF values may be significantly different when SPFs developed from other states’ data are applied. Therefore, CMFs would be biased if SPFs are borrowed from other states without proper adjustments.
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