Safety effects of fixed speed cameras—An empirical Bayes evaluation

  • Published: Accident Analysis & Prevention, Volume 82, September 2015
  • Authors: Hoye, A.
  • Date Added: 05 May 2017
  • Last Update: 05 May 2017
  • Format: html

Objectives:

Assess the safety effects of 223 fixed speed cameras that were installed between 2000 and 2010 in Norway

Methodology:

Before–after empirical Bayes study with control for regression to the mean (RTM). Effects of trend, volumes, and speed limit changes are controlled for as well.

Key Findings:

  • On road sections between 100 m upstream and 1 km downstream of the speed cameras a statistically significant reduction of the number of injury crashes by 22% was found.

  • For killed and severely injured (KSI) and on longer road sections none of the results are statistically significant.

  • However, speed cameras that were installed in 2004 or later were found to reduce injury crashes and the number of KSI on road sections from 100 m upstream to both 1 km and 3 km downstream of the speed cameras.

  • Larger effects were found for KSI than for injury crashes and the effects decrease with increasing distance from the speed cameras. At the camera sites (100 m up- and down-stream) crash reductions are smaller and non-significant, but highly uncertain and possibly underestimated.

Keywords:

Speed camera; Road safety; Crash; Empirical Bayes; Regression to the mean.

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