Safety effects of mobile speed cameras in Norfolk: no more than regression to the mean?

T. Brenac (1, 2)

1 INRETS - Institut National de Recherche sur les Transports et leur Sécurité
2 INRETS/MA - Département Mécanismes d'Accidents

This letter is a comment on the paper by Jones, Sauerzapf and Haynes, "The effects of mobile speed camera introduction on road traffic crashes and casualties in a rural county of England", published in this journal (vol. 39, issue 1, pp. 101-110, 2008). These authors analyse the effects of a camera enforcement programme on injury crashes in the county of Norfolk. The investigation reported is a sound observational before-after accident study. The paper is clear and well documented. It seems, however, that a slight error was made in the calculation of the regression-to-the-mean (RTM) effect, leading to an underestimation of RTM bias. A correction of this error would partly change the conclusions of the paper: based on the corrected results, there is no clear evidence of an overall safety benefit due to the mobile speed camera introduction at the treated sites.

Mots clés: PREVENTION DES ACCIDENTS; CONTROLE; VITESSE MOYENNE; CAMERA VIDEO

Domaines: Traitement des images [eess.IV]

T. Brenac. Safety effects of mobile speed cameras in Norfolk: no more than regression to the mean?. Journal of Safety Research, 2010, Vol41, n1, p65-67. ⟨hal-00506617⟩