Transfer of the Highway Safety Manual predictive method to German rural two-lane, two-way roads

In Germany and Europe in general, a relevant proportion of all \nroad fatalities occur in the nonmotorway rural road network. \nAlthough the predictive performance of most accident prediction \nmodels is unknown, the Highway Safety Manual (HSM) formulation \noffers a consistent method for making reliable crash \nfrequency predictions. These considerations led to the development \nof a model to be used for making crash frequency on \nGerman rural two-lane, two-way road segments following the \nHSM approach. The first step was the development of the \nbase model by fitting a base safety performance function \n(SPF) to a group of 206 base sections, approximately 61 miles \nlong. The full model was subsequently obtained by combining \nthe base SPF with the HSM Crash Modification Factors (CMFs) \nand calibrating the model using the full data set (10,169 sections \napproximately 2,463 miles long). The goodness of fit \n(GOF) of the base and the full model was tested, showing a \ngood fit for both. The GOF of the simple application of the \noriginal HSM predictive method was also tested, showing a \nvery bad fit. This led to the conclusion that the research conducted \nconstitutes a model that combines the consistency of \nthe HSM approach with a good fit to the German reality.