A statistical analysis of the effects of safety cameras on traffic accident rates in Cambridgeshire. Dissertation University of Cambridge.

Author(s)
Hess, S.
Year
Abstract

This report summarizes an investigation into Cambridgeshire's road safety record and the effects of safety cameras on accident frequency and severity on the region's roads. The first part of the analysis looked at the evolution of accident numbers and traffic in Cambridgeshire and Great Britain and went on to compare Cambridgeshire's safety record to the national level. The comparison showed that, when taking into account the disproportional increase in regional traffic over the past ten years, Cambridgeshire actually outperforms the rest of Great Britain in terms of road safety. The second part of the project confirmed the influence of speed, seasonal factors and weather on the frequency and severity of accidents. A detailed time series analysis of the accident date showed the importance of trend and seasonality in the evolution of injury accident numbers. A method was thus developed to remove the influence of these two components from the data so as to ensure that any subsequent comparison between prior and posterior data would be unbiased. The method was also constructed in such a way that it would be able to distinguish between the actual effects of the camera installation and the effects of reversion to mean. The initial investigation into the average effect of safety cameras after detrending and deseasonalising then showed a mean decrease in injury accidents over equal time period by around 18%. However it was decided that simply taking the arithmetic mean of the effects over all sites did not give an accurate description of the overall effects as it did not take into account the relative credibility of single sites. A least squares analysis was thus carried out with the goal of finding the coefficient that best explained the actual effects shown in the data. This showed that the best approximation of the effect of the introduction of a safety camera is a decrease in injury accidents by 31.79%. While this coefficient may be slightly optimistic and specific to the camera sites that were used in this project, the analysis has clearly shown that safety cameras do indeed have a very positive effect on the reduction of accident numbers. (Author/publisher)

Request publication

4 + 7 =
Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.

Publication

Library number
C 28860 [electronic version only]
Source

Cambridge, University of Cambridge, Statistical Laboratory, 2002, XIII + 77 p., 19 ref.

Our collection

This publication is one of our other publications, and part of our extensive collection of road safety literature, that also includes the SWOV publications.