title: Differences in causality factors for single and multi-vehicle crashes on two-lane roads.
abstract: Past research has found a non-linear relationship between traffic intensity or level of service (LOS) and highway crash rates. This paper investigates this relationship further by including the effects of site characteristics and estimating Poisson regression models for predicting single and multi-vehicle crashes separately. Analysis focuses on rural two-lane highways, with hourly LOS, traffic composition, and highway geometric characteristics as independent variables. The resulting models for single and multi-vehicle crashes have different explanatory variables. Single-vehicle crash rates decrease with increasing traffic intensity (lower LOS), shoulder width and sight distance. Multi-vehicle crash rates increase with the number of signals, the daily single-unit truck percentage, and the shoulder width, and decreased on principal arterials compared to other roadway classes. LOS does not significantly explain variation in the number of multi-vehicle crashes. Ongoing research by the authors is aimed at identifying other site factors, such as driveway density and intersection LOS, that can better explain the differing effects reported here and predict crash rates of both types better.
authors.affiliation: Department Civil and Environmental Engineering U-37, University of Connecticut, Connecticut Transportation Institute, Storrs 06269-2037, USA. johnivan@eng2.uconn.edu
authors.forename: J N
authors.initials: JN
authors.lastname: Ivan
authors.forename: R K
authors.initials: RK
authors.lastname: Pasupathy
authors.forename: P J
authors.initials: PJ
authors.lastname: Ossenbruggen
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D015984:Causality; D006801:Humans; D012044:Regression Analysis