Freeway-related safety performance functions (SPFs) in the highway safety manual (HSM) are statistical formulas that were developed based on data from California, Maine, and Washington States. Therefore, HSM recommends modification of SPFs for a certain jurisdiction following a calibration methodology or development of local SPFs to enhance accuracy of predicted crash frequencies. The study estimated calibration factors using the HSM methodology and developed calibration functions using negative binomial method for freeway speed-change lanes in Kansas utilizing crash data from 2013–2015. The quality of estimated calibration factors and calibration functions were assessed using cumulative residual plots. For the calibration, 351 entrance speed-change lanes and 366 exit speed-change lanes were used. The results indicated that HSM methodology consistently underpredicted both fatal and injury and property damage only crashes for both entrance and exit speed-change lanes in Kansas. Since, calibration functions outperformed calibration factors, the study recommends the use of calibration functions for future freeway speed-change lane related decision making in Kansas.
A Comparison between Calibration Factors and Calibration Functions for Predicting Crashes on Freeway Speed-Change Lanes in Kansas
International Conference on Transportation and Development 2019 ; 2019 ; Alexandria, Virginia
2019-08-28
Conference paper
Electronic Resource
English
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