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’).

Click here to download collision and casualty data for permanent speed camera sites in Essex.

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.

fixed-camera

 

  1. Site length: Between 400m and 1500m – This is the length of road that can be used for criteria 2 & 3.
  2. Collisions: A collision severity score is calculated by the formula = 5 x [number of fatal or serious collisions] + [number of slight-injury collisions]. The score for the 36 month baseline period must be at least:
      1. 20 per kilometre for built-up areas.
      2. 16 per kilometre for non-built-up areas.
  3. Traffic speed: Speed survey data showing that the free-flow 85th percentile speed is at or above the enforcement threshold in built-up areas, or 5mph over the maximum speed limit in non-built up areas. In other words, at least 15% of vehicles at the site are going fast enough above the speed limit to be prosecuted for a speeding offence.
  4. Suitability of site: The highway authority must undertake a site survey, demonstrating the following:
    1. The speed limit has been reviewed and confirmed as appropriate.
    2. Analysis into the causes of the collisions included under criteria 2 has demonstrated that camera enforcement is the correct solution – e.g. there is a pattern of excess speed involved in the collisions.
    3. There is no other cost-effective engineering solution that is more appropriate.
    4. That current signage and traffic regulation orders comply with regulations

 

Average speed camera systems

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

specs-index

 

  1. Site length: Between 2km and 20km – This is the length of road that can be used for criteria 2, 3 & 4.
  2. Collisions: A collision severity score is calculated by the formula = 5 x [number of fatal or serious collisions] + [number of slight-injury collisions]. The score for the 36 month baseline period must be at least:
    1. 6 per kilometre for built-up areas.
    2. 4 per kilometre for non-built-up areas.
  3. Collisions: In addition to criteria 2, one of the following must also apply:
    1. At least 1 fatal or serious collision per kilometre during the baseline period. OR
    2. A trend of increasing numbers of slight-injury collisions over time.
  4. Traffic speed: Speed survey data showing that the free-flow 85th percentile speed is at or above the enforcement threshold in built-up areas, or 5mph over the maximum speed limit in non-built up areas. In other words, at least 15% of vehicles at the site are going fast enough above the speed limit to be prosecuted for a speeding offence.
  5. Suitability of site: The highway authority must undertake a site survey, demonstrating the following:
    1. The speed limit has been reviewed and confirmed as appropriate.
    2. Analysis into the causes of the collisions included under criteria 2 has demonstrated that camera enforcement is the correct solution – e.g. there is a pattern of excess speed involved in the collisions.
    3. There is no other cost-effective engineering solution that is more appropriate.
    4. That current signage and traffic regulation orders comply with regulations.