Speed Camera Statistics

Speed Camera Data

Speed camera locations are selected using specific criteria in order to ensure they are deployed in areas with an established pattern of injuries that can be reduced by increasing compliance with the speed limit. The speed camera data that can be downloaded here gives comparisons of collision data before and after the installation of the speed camera.

A 36 month ‘before’ period is used with this comparative data as this is the same time period used when selecting camera locations. This duration is used in order to ensure any collision patterns are well established and not random spikes in road traffic injuries that will return to normal of their own accord (sometimes referred to as ‘regression to mean’).

Download collision and casualty data for permanent speed camera sites in Essex. (Microsoft XLS Document)

Injuries occur in road traffic collisions when the human body absorbs too much of the kinetic energy that is released when a moving vehicle comes to a stop. Kinetic energy increases exponentially with speed, so a doubling of speed will increase kinetic energy by a factor of 4, a trebling of speed increases kinetic energy by a factor of 9. This is why even small reductions in speed can result in major reductions in injuries.

Speed Camera Site Selection Criteria

This section explains the screening criteria used to assess the suitability of locations for installing speed cameras. These criteria are designed to exclude sites that do not have an established pattern of injuries that could realistically be treated by increasing compliance with the speed limit.

It should be noted that these criteria are for guidance only, and ultimately the highway authority will make a decision on a site-by-site basis, judging each proposed scheme on its merits.

A 36 month ‘baseline‘ period (referred to below) is used when selecting camera locations in order to ensure any collision patterns are well established and not random spikes in road traffic injuries that will return to normal of their own accord (an example of ‘regression to mean’ described above).

Spot speed camera systems

These are the familiar “Gatso” type speed cameras usually seen on urban roads.

Criteria is currently under review.

Average speed camera systems

This type of system measures average speed between camera sites and is most commonly seen on trunk roads and motorways.

Criteria is currently under review.