21 February 2018

Red light enforcement cameras

This review on the use of red light enforcement cameras was conducted by Dr Chloe Perkins and Dr Rebecca Steinbach of the London School of Hygiene and Tropical Medicine.

What is the systematic review about?

The aim of this review was to update the existing Cochrane systematic review of red-light cameras, and explore the circumstances in which they work. The review identified 38 studies relating to the use of red-light cameras and the evidence presented below comes from a synthesis of these studies. 

This review provides evidence that red light cameras are an effective intervention for reducing 'red-light running' and can help combat most types of road traffic crashes resulting in injury. However, there was evidence that red light cameras were also associated with increases in one particular type of road traffic crashes: rear-end crashes. Given continued increases in traffic volume and limited police budgets, red light cameras appear to be a viable way of protecting public health and safety. However, the potential benefits of a reduction in traffic violations and injuries caused by most types of crashes should be balanced with the increased risk of rear-end crashes.

What does it tell us about the impact of red-light cameras?

The evidence evaluated in this updated review shows red light cameras reduce both red-light violations and most types of road traffic crashes which result in injury. Results suggest that the implementation of red-light camera programmes is associated with a:

  • 61% reduction in red-light violations
  • 20% reduction in road traffic crashes resulting in injuries
  • 24% reduction in right angle crashes
  • 29% reduction in right angle crashes resulting in injuries
  • 19% increase in rear-end crashes

There was no evidence that the effect of red-light cameras differed by country.

How do red-light cameras make an impact?

Red light cameras work through deterrence, both specific and general. Specific deterrence focuses primarily on apprehending and punishing individual offenders, and assumes that once caught and brought to justice, they will consequently avoid re-offending. General deterrence focuses on the wider population and assumes the threat of punishment will deter people from running red lights, to avoid legal consequence. The greater the perception of risk of punishment, the greater the likelihood that general deterrence will be effective.  

In which contexts do they work best?

The effect of red light camera interventions might differ by time and day of week, signal timing, or average daily traffic.  However, there was not enough information in the primary studies to analyse these potential moderators. The review did examine whether the effect of red light cameras differed by country (USA and Australia) but found few differences in the effect of red light cameras on most outcomes.

How do you implement them to get the best impact?

Many of the studies in the review highlighted that public knowledge of the implementation of a red light camera intervention was essential for its success.  Red light camera programmes often included publicity campaigns and warning signs to increase driver awareness of the cameras to enhance their deterrent effect.  This review explored the effect of using warning signs to highlight that a red light safety camera was in place.  However, no significant difference in crashes and injury crashes was found when warning signs were used with the red light safety camera intervention.

What do they cost?

Many of the studies in the review did not include any economic information; those that did varied widely in the amount of detail provided. None of the studies conducted a full cost-benefit analysis that included both fiscal viability and societal benefits (including crash costs).  While studies examining fiscal viability in the USA and Australia found mixed results, an early cost benefit analysis in the UK identified significant benefits for red light cameras with most areas able to achieve a net benefit within one year.  

This review is the eleventh in the What Works: Crime Reduction Systematic Review Series.

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