Safety Cameras

Safety Cameras

How Effective?

This section provides some details of how effective safety camera interventions can be.

Impact on speed reduction

Increased vehicle speeds increase the risk of RTIs and the severity of these RTIs when they occur. Therefore, the effectiveness of safety cameras in reducing vehicle speeds plays an important role in preventing RTIs.

  • The introduction of speed cameras has reduced excessive speeding. This conclusion is based on a substantial body of evidence across a large number of partnership areas. Speed surveys also confirmed that these reductions were sustained over time. At the vast majority of sites where safety cameras were introduced there was a reduction in vehicle speed. The reduction in vehicle speed was particularly noticeable in urban areas (30 mph or 40 mph limits) where average speed fell by around 7 per cent. Speed in rural areas (over 40 mph) fell by 3 per cent on average. There was a 31 per cent overall reduction in the proportion of vehicles breaking the speed limit at new camera sites. This was most noticeable at fixed camera sites, where the number of vehicles exceeding the speed limit dropped by 70 per cent, compared to 18 per cent at mobile sites.

(A. Gains et al., 2005)

  • Cameras are a very effective way of persuading drivers not to speed, and thereby reducing the number of people killed and seriously injured. An evaluation of their effectiveness in 2005 showed that they were saving around 100 lives a year, and preventing over 1,600 serious injuries. 

(RoSPA, 2011)

  • The Cochrane Review found that post installation of cameras, there was a reduction in the proportion of speeding vehicles (drivers) over the accepted posted speed limit ranging from 8 per cent to 70 per cent. Most countries reported reductions in speed in the 10 to 35 per cent range.

(C. Wilson et al., 2011)

  • Although the free flow speed measurements have been made at a rather small number of sites, they do clearly indicate the improving compliance with speed limits on built-up roads since 1998 and on motorways since 2003.This suggests that a combination of enforcement and education is gradually changing attitudes to speeding, particularly in urban areas, in the same way that attitudes to drinking and driving were changed in the 1970s and 1980s.

(C. Mitchell, 2012)

Owen (2010) reviewed the impact of widely publicising the speed camera switch-off in Oxfordshire.

  • The results, although only at a limited number of locations for a short period of time, indicate that motorists do alter their speed choices when they know a fixed speed camera is not loaded.

  • Even the most conservative analysis shows a 2.9 to 4 times increase in offending at sites only one month after the switch-off.

  • If seasonal variations and more recent offence rates are taken into account then the increases are significantly higher.

  • Local authorities around the country should bear these results in mind if they are considering a similar approach to Oxfordshire as the deterrent effect of the housing alone is diminished by public announcements regarding their operational capacity.

(R. Owen, 2010)

  • In a later study, the same author found that the positive safety effect of speed cameras extends even post cameras being switched off.

(R. Owen, 2015)

One experiment used a driving simulator to try to identify an optimal enforcement approach.

  • It looked at four different scenarios: overt cameras with a delay to receiving the fine; overt cameras with immediate feedback; covert cameras with a delay to receiving the fine; and covert cameras with immediate feedback.

  • The results shows that both median speed and speed variance were higher with overt rather than covert cameras. Moreover, implementing a covert camera system with immediate feedback was more conducive to drivers maintaining steady speeds at the permitted levels from the very beginning.

  • Finally, both ‘overt cameras’ groups exhibited more kangaroo effect in driving patterns throughout the experiment. The study concluded that an implementation strategy consisting of covert speed cameras combined with immediate feedback to the offender is potentially an optimal way to motivate drivers to maintain speeds at the speed limit. However, this approach is more resource-intensive than an automated processing system.

(Marciano et al., 2015)

Impact on injury reduction

  • In a systematic review of 28 studies, all the studies included found a lower number of RTIs in the speed camera areas after implementation of the programme.

  • In the vicinity of camera sites, the reductions ranged from 8 per cent to 49 per cent for all RTIs, with reductions for most studies in the 14 per cent to 25 per cent range.

  • For injury RTIs, the decrease ranged between 8 per cent and 50 per cent, and for RTIs resulting in fatalities or serious injuries the reductions were in the range of 11 per cent to 44 per cent.

  • Effects over wider areas showed reductions for all RTIs ranging from 9 per cent to 35 per cent, with most studies reporting reductions in the 11 per cent to 27 per cent range. For RTIs resulting in death or serious injury, reductions ranged from 17 per cent to 58 per cent, with most studies reporting this result in the 30 per cent to 40 per cent reduction range.

(C. Wilson et al., 2011)

  • Safety cameras are one of the reasons why fatalities on the road have fallen from around 5,000 a year at the start of the 1990s to fewer than 2,000 in 2010, and they must continue to play their part in the UK’s future road safety strategy. A further review of the evidence of the effectiveness of speed cameras, taking into account other factors, concluded that in the year ending March 2004, cameras at more than 4,000 sites across Great Britain prevented some 3,600 personal injury RTIs, saving around 1,000 people from being killed or seriously injured.

(RoSPA, 2011)

  • The number of people killed or seriously injured at safety camera sites is 68 per cent lower after camera enforcement. The number of personal injury RTIs at safety camera sites is 48 per cent lower after enforcement.

(Scottish Safety Camera Partnership, 2012)

  • A review of average speed camera effectiveness at a number of sites throughout the UK showed a positive impact on injury reduction:

    • In Nottinghamshire, KSI figures reduced by an average of 65 per cent (across eleven roads equipped with average speed enforcement in 2000);

    • In Northamptonshire, KSI figures reduced by 60 per cent on the A43 Lumbertubs Way and 85 per cent on the A428 (equipped in 2001);

    • In South Yorkshire, KSI figures reduced by 82 per cent on the A616 Stocksbridge Bypass Trans-Pennine Route (equipped in 2003); and

    • In Strathclyde (Scotland), KSI figures reduced by 37 per cent across the A77, where there is an entire 32 mile controlled zone (equipped in 2005).

  • The experience gathered so far indicates that average speed enforcement is an efficient speed enforcement method, leading to reductions in speeds across entire sections of roads and reductions in the number of RTIs and casualties.

(ETSC, 2009)

  • A comprehensive study undertaken by RAC Foundation & Road Safety Analysis on the levels of occurrence of collisions before and after average speed camera (ASC) systems’ installation (with consideration for site-selection period, regression-to-mean and trend effect) found

    • A 36.4% reduction in the mean rate of fatal and serious collisions (FSC) after the system’s installation;

    • A 16% reduction in the mean rate of personal injury collisions (PIC) after the system’s installation;

    • A 42.2% reduction in the mean rate of FSCs for low speed sites and a 32.3% reduction in the mean rate of FSCs for high speed sites;

    • A 25% reduction in the mean rate of PICs at the low speed sites and a 7.9% reduction in the mean rate of PICs for high speed sites.

(R. Owen, G. Ursachi and R. Allsop, 2016)

  • Meta-analysis of 19 speed camera studies (fixed and average) found a total reduction in crash numbers of about 20 per cent.
  • It found that the effect declines with increasing distances from the camera location. Fatal crashes were found to be reduced by 51 per cent although this result may be affected by regression to the mean. The results indicate that kangaroo driving (braking and accelerating) occurs, but no adverse effects on speed or crashes were found.

  • It also found that crash migration may occur but is not common.

(Høye, 2014) 

  • The DfT camera review found that there has been a significant reduction in casualties at camera sites.

  • There was a 42 per cent reduction in the number of KSIs at sites where safety cameras were introduced. Overall, this equates to around 1,745 fewer KSI casualties per annum, though this is subject to some reduction due to regression-to-mean effects.

  • There was a 22 per cent reduction in the number of personal injury RTIs at camera sites. Overall, this equates to around 4,230 fewer personal injury RTIs per annum, though this is subject to a reduction due to regression-to-mean that is probably modest in scale.

  • There were reductions in personal injury RTIs and KSI casualties at both fixed and mobile safety camera sites. The former appeared to be the most effective – on average, the number of killed or serious injuries fell by around 50 per cent at fixed sites, and by around 35 per cent at mobile sites. These results were found to be consistent with speed surveys.

  • There were over 100 fewer people killed per annum at camera sites after implementation.

  • There was a 32 per cent reduction in the number of child KSIs at camera sites.

  • There was a 29 per cent reduction in the number of pedestrians KSIs at camera sites.

(A. Gains et al., 2005)

  • Percentage reductions in RTIs and casualties differ between fixed and mobile, and between urban and rural camera sites. Judging from the evidence, the operation of cameras at over 4,000 sites of all types resulted in around 1,000 fewer KSIs in the vicinity of cameras in the year ending March 2004.

(R. Allsop, 2010)

  • Existing research consistently shows that speed cameras are an effective intervention in reducing RTIs and related casualties.

  • The level of evidence is relatively poor, however, as most studies did not have satisfactory comparison groups or adequate control for potential confounders.

  • Controlled introduction of speed cameras with careful data collection may offer improved evidence of their effectiveness in the future.

(P. Pilkington, and S. Kinra, 2005)

  • The contribution of safety cameras shows up particularly clearly in highly urbanised and high injury risk areas but there is little evidence of any statistically significant impact elsewhere.

(G. Hindle and T. Hindle, 2011)

One study controlling for regression to the mean was a before-after Empirical Bayes study looking at the safety effects of 223 fixed speed cameras installed between 2000 and 2010 in Norway.

  • It found a statistically significant reduction in the number of injury collisions of 22 per cent up to 1km downstream of the camera.

(Høye, 2015)

Another study published recently looked to evaluate the impacts of speed limit enforcement cameras on reducing accidents in the UK by accounting for both confounding factors and the selection of proper reference groups.

  • They used the propensity score matching (PSM) method as well as a naïve before and after approach and Empirical Bayes (EB). They observed 771 treatment and 4787 potential reference sites over 9 years in England.

  • The study found that both the PSM and EM methods show similar results that there are significant reductions in the number of accidents of all severities at speed cameras sites. Speed cameras were found to be most effective in reducing accidents up to 200 metres from camera sites and no evidence of collision migration was found.

(Li et al., 2013)

Economic value of cameras

  • The DfT four year evaluation of safety cameras estimated that the annual economic benefit of cameras in place at the end of the fourth year was over £258 million, compared with enforcement costs of about £96 million.

(RoSPA, 2011)

  • In the past local authorities and the police often had insufficient funds to make fullest use of cameras to deal with the problem of speeding.

  • Enforcement had to compete with other priorities from their limited budget allocations and some areas could not afford any automatic enforcement.

  • In 1998 the Government decided to resolve this by changing HM Treasury rules to allow penalties from speeding and traffic signal offences to be “netted-off” to pay for the costs of purchase, operation and administration of safety camera enforcement.

  • The pilot project was designed to test the funding system and to show that cameras continued to be an effective road safety intervention under the different operational arrangement.

  • At fixed camera sites 85th percentile speeds are down by 8 mph, and at mobile sites by 3 mph.

  • Overall the pilot areas outperformed the rest of Great Britain by about 2:1 in casualty reduction.

  • These results suggest that the safety camera partnership funding mechanism was successful.

(A. Waddams, 2003)

Since the above paper was written many local authorities have now taken over the management of safety cameras in various regions but the funding mechanism is still essentially the same.

  • The new funding mechanism and partnership arrangements for safety cameras were found to have worked well.

  • In the fourth year, the programme had released around £96 million per annum (in England, Wales and Scotland) for local partnerships to invest in safety camera enforcement and supporting education.

(A. Gains et al., 2005)

Since the Gains et al. paper was published in 2005, there have been further changes, and decisions about enforcement are now made locally, rather than nationally. In some areas this has resulted in a substantial reduction in enforcement activity.

While the papers above show the effect of reduced enforcement on speed, there is no solid evidence available relating to the effect on casualties. Given the long-standing relationship that has been proved between speed and casualty rates and severity, it might be expected that the number and severity of RTIs would increase in those areas where enforcement is reduced substantially. For example, Northamptonshire stopped all fixed enforcement and in the following year fatalities approximately doubled from 19 to 36. However, the data set is too small and complex, and of short duration, to draw any definitive conclusions.

Gaps in the research

While numerous reports provide evidence for the reduction in speed and RTIs provided by safety cameras, there are also a number of studies (predominantly academic ones) which call for research using more robust evidence and statistical analysis.

  • More studies of a scientifically rigorous and similar nature are necessary to provide the answer to the magnitude of effect.

(C. Wilson et al., 2011)

  • The level of evidence is relatively poor, however, as most studies did not have satisfactory comparison groups or adequate control for potential confounders.

  • Controlled introduction of speed cameras with careful data collection may offer improved evidence of their effectiveness in the future.

(P. Pilkington, and S. Kinra, 2005)

Strengthening the evidence base with more rigorous data would be an area which might benefit from further effort. Additional academic evidence and analysis may help to finally settle the debate of the effectiveness of speed cameras.

The majority of reports focus on fixed point safety cameras and there appears to be a limited amount of research providing evidence on the safety benefits of red light cameras and average speed cameras (particularly in the UK).

  • Date Added: 03 Apr 2012, 03:02 PM
  • Last Update: 11 Dec 2017, 04:11 PM