Effects of Geometric Characteristics on Head-On Crash Incidence on Two-Lane Roads in Connecticut

Abstract

Negative binomial generalized linear models were used to evaluate the effects of roadway geometric features on the incidence of head-on crashes on two-lane rural roads in Connecticut. Six hundred fifty-five highway segments—each with a uniform length of 1 km and no intersections with signal or stop control on the major road approaches—were selected for analysis. Head-on crash data were collected for these segments from 1996 through 2001. Variables found to influence the incidence of head-on crashes significantly were speed limit, sum of absolute change rate of horizontal curvature, maximum degree of horizontal curve, and sum of absolute change rate of vertical curvature. Three models were estimated with different combinations of these four variables, and the performance of the models was tested by using Akaike's information criterion. The number of crashes was found to increase with each of these variables except for speed limit. Variables such as lane and shoulder width were not found to be significant for explaining the incidence of head-on crashes. The results suggest that to reduce the incidence of head-on crashes on two-lane roads, it is more effective to reduce the number and degree of horizontal and vertical curves than to widen the pavement.