Do speed cameras reduce collisions and related casualties?
This was the question I attempted to answer by conducting a systematic review of the evidence and a local evaluation of cameras in Avon and Somerset. The results are good news for road safety.
Road traffic collisions are an important cause of death and disability in the UK. Each year around 3,500 people are killed and 330,000 injured on roads in Britain. UK research estimates that at least one third of collisions may be speed-related. Speeding traffic also has wider health impacts. It can discourage walking and cycling, which can impact upon quality of life and general physical activity levels. This has effects on health outcomes such as Coronary Heart Disease and obesity.
Speed cameras are being increasingly used to help reduce traffic speed and in turn, collisions and casualties. But cameras are controversial, with accusations sometimes made that their presence is only a money-making exercise.
I conducted the literature review on behalf of the South West Public Health Observatory, to help develop the evidence base around injury prevention interventions. The review of literature identified nine studies from around the world. All suggested that the introduction of speed cameras are associated with a short term (less than 3 years post camera introduction) reduction in collisions and casualties, both at camera sites and across the wider area. Three studies were of average quality whilst the rest were average/poor or poor. There was a lack of good quality evidence on long term effects.
I carried out the local evaluation in association with the Avon and Somerset Safety Camera Partnership. They are a multi-agency group tasked with managing speed cameras in the local area, and ensuring that they are effective. I examined speed cameras in Avon and Somerset between 1993-2001, based on data provided to me by the partnership. I examined collisions and casualties at each camera site, looking at five years before data and at least 3 years after data. The analysis revealed that the introduction of cameras is associated with a statistically significant before-after reduction in collisions and Killed and Seriously Injured (KSI) casualties at camera sites. The results also suggest that cameras may be most effective at reducing the most serious health outcomes (fatalities and serious injuries).
A comparison of collisions, casualties and vehicle speeds between camera sites and control sites (sites where cameras are due to be erected) from 1998-2000 showed that camera sites are associated with statistically significant lower rates of collisions, KSI casualties and percentage of speeding vehicles when compared to control sites. Interestingly, there was no significant change in those travelling greater than 15mph over the speed limit.
The work suggests that speed cameras are effective in reducing collisions and casualties, and are therefore an important public health intervention.
Paul Pilkington, Public Health based with Bristol S&W Primary Care Trust
