20mph zones and Road Safety in London

  • Published: A report to the London Road Safety Unit (2008)
  • Authors: Grundy, C., Steinbach, R., Edwards, P., Wilkinson, P. and Green, J.
  • Date Added: 07 Apr 2016
  • Last Update: 07 Apr 2016
  • Format: pdf


The study aimed to provide robust evidence on the effects of 20mph zones in London


  • Describing 20mph zones in London using Geographic Information Systems;

  • Quantifying the effects of 20mph zones on collision and casualty risk;

  • Assessing whether 20mph zones change the pattern of injuries for local residents compared with non-local travellers;

  • Quantifying the cost-effectiveness of 20mph zones in terms of the number of casualties prevented against the cost of implementation;

  • Assessing the potential casualty reductions in London from future expansion of the number/size of 20mph zones

Key Findings

The study provides robust evidence for the beneficial effects of 20mph zones on road safety in London, with the best estimate of the overall effect being a reduction in all casualties of 42% compared with outside areas


London, 20mph schemes, policy and practice, effect of 20mph zones


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