Using multivariate adaptive regression splines (MARS) to develop crash modification factors for urban freeway interchange influence areas

► We develop crash modification factors (CMFs) for urban interchange areas in Florida. ► We apply multivariate adaptive regression splines (MARS) to develop CMFs. ► CMFs are developed for median width and inside and outside shoulder widths. ► A 2-ft increase in the inside shoulder reduces fatal and injury crashes by 33%. ► A 42-ft reduction in the median width increases total crashes by 263%.