Citation

Mountain L, Fawaz B, Sineng L. Traffic Eng. Control 1992; 33(7-8): 429-431.

Affiliation

Univ of Liverpool, Liverpool, England.

Copyright

(Copyright © 1992, Hemming Group)

DOI

unavailable

PMID

unavailable

Abstract

If sites are selected for accident remedial treatment at least partly on the basis of a high observed accident frequency in a particular time period, then the observed accident frequency is likely to fall after treatment, even if the treatment has had no effect. This, so-called, 'regression-to-mean' effect leads to over-estimates of treatment effectiveness. A number of methods have been proposed for estimating the magnitude of the regression-to-mean effect and hence the true treatment effect. In a previous paper the authors compared the performance of three such methods with the estimates obtained from a straightforward before-and-after comparison of accident frequencies at treated intersections. In this paper, the analysis is extended to cover the performance of the methods at link sites. Link sites are somewhat more difficult to deal with than intersections because account must be taken of the length of the link segment.