Urban Speed Management Methods

  • Published: TRL, 1998
  • Authors: A.M. Mackie
  • Date Added: 05 Feb 2013
  • Last Update: 25 Oct 2016
  • Format: html


To review and evaluate the measures needed for successful 20 mph zones.


The predominant methodology employed was an in depth literature review of UK and international research. Speed measurements were also gathered before and after the installation of speed signs to assess their effectiveness.

Key Findings:

  • Of all the methods reviewed (including speed cameras, and various types of signs) traffic calming measures were clearly the most effective achieving reductions in mean speed of 9.3 mph and 85th percentile speed reductions of 10.4 mph.

  • Physical measures such as speed humps are therefore the most effective at enforcing 20 mph zones.

  • The majority of sign only zones which were reviewed did not show any reduction in RTIs, although small speed reductions were recorded.

  • Effective public awareness campaigns and/or enforcement can slightly increase the effectiveness of all measures, in some cases achieving additional speed reductions of 3 mph.

  • The use of flashing signs and speed cameras have a substantial effect on speed reduction and appear likely to have safety benefits at specific locations.

  • However, their costs may preclude them from being used as a comprehensive method of speed control across a whole urban zone.


Traffic calming, Speed reductions, Effectiveness.


Reviewing traffic calming methods in 20 mph zones. Older research – some advancements will have been made (e.g. in cameras) but basic premise of the methods that are reviewed haven’t changed significantly.