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Road traffic congestion and crash severity: econometric analysis using ordered response models
journal contribution
posted on 2011-04-08, 09:24 authored by Mohammed Quddus, Chao Wang, Stephen IsonThere is an ongoing debate among transport planners and safety policy makers as to whether there is any association between
the level of traffic congestion and road safety. One can expect that the increased level of traffic congestion aids road safety and this is
because average traffic speed is relatively low in a congested condition relative to an uncongested condition, which may result in less
severe crashes. The relationship between congestion and safety may not be so straightforward, however, as there are a number of other
factors such as traffic flow, driver characteristics, road geometry, and vehicle design affecting crash severity. Previous studies have
employed count data models either Poisson or negative binomials and their extensions while developing a relationship between the
frequency of traffic crashes and traffic flow or density as a proxy for traffic congestion . The use of aggregated crash counts at a road
segment level or at an area level with the proxy for congestion may obscure the actual relationship. The objective of this study is to
explore the relationship between the severity of road crashes and the level of traffic congestion using disaggregated crash records and a
measure of traffic congestion while controlling for other contributory factors. Ordered response models such as ordered logit models,
heterogeneous choice models, and generalized ordered logit (partially constrained) models suitable for both ordinal dependent variables
and disaggregate crash data are used. Data on crashes, traffic characteristics e.g., congestion, flow, and speed , and road geometry e.g.,
curvature and gradient were collected from the M25 London orbital motorway between 2003 and 2006. Our results suggest that the level
of traffic congestion does not affect the severity of road crashes on the M25 motorway. The impact of traffic flow on the severity of
crashes, however, shows an interesting result. All other factors included in the models also provide results consistent with existing studies.
History
School
- Architecture, Building and Civil Engineering
Citation
QUDDUS, M.A., WANG, C. and ISON, S.G., 2010. Road traffic congestion and crash severity: econometric analysis using ordered response models. Journal of Transportation Engineering, 136 (5), pp. 424-435.Publisher
© American Society of Civil EngineersVersion
- AM (Accepted Manuscript)
Publication date
2010ISSN
0733-947X;1943-5436Publisher version
Language
- en