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留学生论文网:Accident Analysis and Prevention:Analy

Accident Analysis and Prevention 40 (2008) 1674–1682
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Accident Analysis and Prevention
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Analysis of left-turn crash injury severity by conflicting pattern using partial
proportional odds models
XuesongWang∗, Mohamed Abdel-Aty
Department of Civil & Environmental Engineering, University of Central Florida, Orlando, FL 32816-2450, United States
a r t i c l e i n f o
Article history:
Received 19 October 2007
Received in revised form 24 May 2008
Accepted 2 June 2008
Signalized intersection  Left-turn crash  Conflicting pattern  Crash injury severity  Partial proportional odds model  Significant factor
a b s t r a c t
The purpose of this study is to examine left-turn crash injury severity. Left-turning traffic colliding withopposing through traffic and with near-side through traffic are the two most frequently occurring conflictingpatterns among left-turn crashes (Patterns 5 and 8 in the paper, respectively), and they are proneto be severe. Ordered probability models with either logit or probit function is commonly applied in crashinjury severity analyses; however, its critical assumption that the slope coefficients do not vary over differentalternatives except the cut-off points is usually too restrictive. Partial proportional odds models aregeneralizations of ordered probability models, for which some of the beta coefficients can differ acrossalternatives,were applied to investigate Patterns 5 and 8, and the total left-turn crash injuries. The resultsshowthat partial proportional odds models consistently perform better than ordered probability models.By focusing on specific conflicting patterns, locating crashes to the exact crash sites and relating approachvariables to crash injury in the analysis, researchers are able to investigate how these variables affectleft-turn crash injuries. For example, opposing through traffic and near-side crossing through traffic inthe hour of collision were identified significant for Patterns 5 and 8 crash injuries, respectively. Protectedleft-turn phasing is significantly correlated with Pattern 5 crash injury. Many other variables in driverattributes, vehicular characteristics, roadway geometry design, environmental factors, and crash characteristicswere identified. Specifically, the use of the partial proportional formulation allows a much betteridentification of the increasing effect of alcohol and/or drug use on crash injury severity, which previouslywas masked using the conventional ordered probability models.
© 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Intersections are among the most dangerous locations of a roadwaynetwork. In the state of Florida, 43.1% of fatalities and seriousnjuries occurred at or were influenced by intersections (FloridaDepartment of Transportation, 2006). In the U.S., although onlyaround 10% of all intersections are signalized, in 2005, nearly 30%(2744) of intersection fatalities occurred at signalized intersections(Rice, 2007). Left-turn crashes occur frequently and they accountfor a high percentage of total crashes at signalized intersections.

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