Speed cameras, section control, and kangaroo jumps – a meta-analysis

  • Published: Accident Analysis & Prevention, Volume 73, December 2014
  • Authors: A. Høye
  • Date Added: 11 Feb 2016
  • Last Update: 11 Feb 2016
  • Format: html

Objectives:

To undertake a meta-analysis to determine the effect of speed cameras and section control on crash rates.

Methodology:

A meta-analysis of 63 effect estimates from 15 speed camera studies and five effect estimates from four section control studies

Key Findings:

  • The effect of speed cameras and section control on crashes were investigated by means of meta-analysis. 63 effect estimates from 15 studies of the effects of speed cameras on crashes and five effect estimates from four studies of the effect of section control on crashes were included in the meta-analysis.

  • Speed cameras were found to reduce the total number of crashes by about 20 per cent. The results from meta-analysis and sensitivity analysis do not indicate that this result is likely to be affected by regression to the mean (RTM), publication bias or outlier bias. Sponsorship bias (more favourable effects from studies sponsored by government agencies) may have occurred, but the number of studies sponsored by non-government agencies is so small (two studies) that the results must be treated with caution.

  • The effect on total crash numbers was found to decrease with increasing distance from the camera locations. While crashes were found to be reduced by 18 per cent at the camera locations (±250m), the effect was found to decline to a reduction of 4 per cent at a distance of 1km or more from the camera location (in both directions). The overall effect of -20 per cent for total crash numbers refers to unspecified distances from the camera locations.

  • For section control, a considerably larger reduction on total crash numbers was found (30 per cent), and a reduction of the number of KSI crashes by 56 per cent. Neither of these results is likely to be affected by RTM.

  • A possible explanation for the seeming lack of RTM effects on the results for total crash numbers is that only the most serious crashes are used as a criterion for choosing camera locations. Total crash numbers would then not necessarily be exceptionally high at camera locations before the installation of speed cameras or speed control. Unfortunately, no detailed information is available from the studies included in the meta-analysis about the criteria for installing speed cameras.

Comments:

Robust investigation into the effects of fixed and average speed cameras on crash rates.

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