Congestion and Safety: A Spatial Analysis of London

31 Pages Posted: 6 Sep 2004

See all articles by Robert B. Noland

Robert B. Noland

Imperial College London

Mohammed A. Quddus

Imperial College London

Date Written: August 2003

Abstract

A disaggregate spatial analysis, using enumeration district data for London was conducted with the aim of examining how congestion may affect traffic safety. It has been hypothesized that while congested traffic conditions may increase the number of vehicle crashes and interactions, their severity is normally lower than crashes under uncongested free flowing conditions. This is primarily due to the slower speeds of vehicles when congestion is present. Our analysis uses negative binomial count models to examine whether factors affecting casualties (fatalities, serious injuries and slight injuries) differed during congested time periods as opposed to uncongested time periods. We also controlled for congestion spatially using a number of proxy variables and estimated pedestrian casualty models since a large proportion of London casualties are pedestrians. Results are not conclusive. Our results suggest that road infrastructure effects may interact with congestion levels such that in London any spatial differences are largely mitigated. Some small differences are seen between the models for congested versus uncongested time periods, but no conclusive trends can be found. Our results lead us to suspect that congestion as a mitigator of crash severity is less likely to occur in urban conditions, but may still be a factor on higher speed roads and motorways.

Keywords: transport safety, congestion, negative binomial model

JEL Classification: R40, R41

Suggested Citation

Noland, Robert B. and Quddus, Mohammed A., Congestion and Safety: A Spatial Analysis of London (August 2003). Available at SSRN: https://ssrn.com/abstract=586042 or http://dx.doi.org/10.2139/ssrn.586042

Robert B. Noland (Contact Author)

Imperial College London ( email )

South Kensington Campus
Exhibition Road
London SW7 2AZ, SW7 2AZ
United Kingdom

Mohammed A. Quddus

Imperial College London ( email )

South Kensington Campus
Exhibition Road
London SW7 2AZ, SW7 2AZ
United Kingdom

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