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Congestion and safety: A spatial analysis of London


  • Noland, Robert B.
  • Quddus, Mohammed A.


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.

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  • Noland, Robert B. & Quddus, Mohammed A., 2005. "Congestion and safety: A spatial analysis of London," Transportation Research Part A: Policy and Practice, Elsevier, vol. 39(7-9), pages 737-754.
  • Handle: RePEc:eee:transa:v:39:y:2005:i:7-9:p:737-754

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    References listed on IDEAS

    1. Daniel Shefer & Piet Rietveld, 1997. "Congestion and Safety on Highways: Towards an Analytical Model," Urban Studies, Urban Studies Journal Limited, vol. 34(4), pages 679-692, April.
    2. Dickerson, Andrew & Peirson, John & Vickerman, Roger, 2000. "Road Accidents and Traffic Flows: An Econometric Investigation," Economica, London School of Economics and Political Science, vol. 67(265), pages 101-121, February.
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    Cited by:

    1. Stefan Bauernschuster & Timo Hener & Helmut Rainer, 2017. "When Labor Disputes Bring Cities to a Standstill: The Impact of Public Transit Strikes on Traffic, Accidents, Air Pollution, and Health," American Economic Journal: Economic Policy, American Economic Association, vol. 9(1), pages 1-37, February.
    2. Holguín-Veras, José, 2011. "Urban delivery industry response to cordon pricing, time-distance pricing, and carrier-receiver policies in competitive markets," Transportation Research Part A: Policy and Practice, Elsevier, vol. 45(8), pages 802-824, October.
    3. Fosgerau, Mogens & Lindsey, Robin, 2013. "Trip-timing decisions with traffic incidents," Regional Science and Urban Economics, Elsevier, vol. 43(5), pages 764-782.
    4. Holgui­n-Veras, Jose & Cetin, Mecit & Xia, Shuwen, 2006. "A comparative analysis of US toll policy," Transportation Research Part A: Policy and Practice, Elsevier, vol. 40(10), pages 852-871, December.
    5. Peck, Dana & Scott Matthews, H. & Fischbeck, Paul & Hendrickson, Chris T., 2015. "Failure rates and data driven policies for vehicle safety inspections in Pennsylvania," Transportation Research Part A: Policy and Practice, Elsevier, vol. 78(C), pages 252-265.
    6. Ilias-Nikiforos Pasidis, 2015. "Congestion by accident? Traffic and accidents in England," ERSA conference papers ersa15p1321, European Regional Science Association.
    7. Robert Noland & Mohammed Quddus & Washington Ochieng, 2008. "The effect of the London congestion charge on road casualties: an intervention analysis," Transportation, Springer, vol. 35(1), pages 73-91, January.
    8. Holgun-Veras, Jos & Cetin, Mecit, 2009. "Optimal tolls for multi-class traffic: Analytical formulations and policy implications," Transportation Research Part A: Policy and Practice, Elsevier, vol. 43(4), pages 445-467, May.

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