title: Analysis of the injury severity of crashes by considering different lighting conditions on two-lane rural roads.
abstract: BACKGROUND
  Many studies have examined different factors contributing to the injury severity of crashes; however, relatively few studies have focused on the crashes by considering the specific effects of lighting conditions. This research investigates lighting condition differences in the injury severity of crashes using 3-year (2009-2011) crash data of two-lane rural roads of the state of Washington.
  
  
  METHODS
  Separate ordered-probit models were developed to predict the effects of a set of factors expected to influence injury severity in three lighting conditions; daylight, dark, and dark with street lights. A series of likelihood ratio tests were conducted to determine if these lighting condition models were justified.
  
  
  RESULTS
  The modeling results suggest that injury severity in specific lighting conditions are associated with contributing factors in different ways, and that such differences cannot be uncovered by focusing merely on one aggregate model. Key differences include crash location, speed limit, shoulder width, driver action, and three collision types (head-on, rear-end, and right-side impact collisions).
  
  
  CONCLUSIONS
  This paper highlights the importance of deploying street lights at and near intersections (or access points) on two-lane rural roads because injury severity highly increases when crashes occur at these points in dark conditions.
authors.affiliation: Civil Engineering Department, K.N. Toosi University of Technology, Tehran, Iran. Electronic address: alirezajafari.kntu@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Jafari Anarkooli
authors.affiliation: Civil Engineering Department, K.N. Toosi University of Technology, Tehran, Iran. Electronic address: Mansour@Kntu.ac.ir.
authors.forename: M
authors.initials: M
authors.lastname: Hadji Hosseinlou
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D006801:Humans; D008029:Lighting / Q000706:statistics & numerical data*; D008962:Models, Theoretical; D012424:Rural Population
keywords: Fixed effects; Injury severity; Lighting condition; Ordered probit; Rural roads