Traffic Law Enforcement: A review of the literature

Monash University Accident Research Centre - Report #53 - 1994

Author: D. Zaal

Full report in .pdf format [880KB]


A study was undertaken to review the recent Australian and international literature relating to traffic law enforcement. The specific areas examined included alcohol, speed, seat belts and signalised intersections. The review documents the types of traffic enforcement methods and the range of options available to policing authorities to increase the overall efficiency (in terms of cost and human resources) and effectiveness of enforcement operations. The review examines many of the issues related to traffic law enforcement including the deterrence mechanism, the effectiveness of legislation and the type of legal sanctions administered to traffic offenders. The need to use enforcement in conjunction with educational and environmental/engineering strategies is also stressed. The use of educational programs and measures targeted at modifying the physical and social environment is also briefly reviewed. The review highlights the importance of developing enforcement strategies designed to maximise deterrence whilst increasing both the perceived and actual probability of apprehension. The use of Random Breath Testing (RBT), automated speed and red light enforcement cameras and selective enforcement programs are highlighted. The need for publicity to support enforcement operations, police training and education programs is also documented. The review concludes with a series of recommendations regarding the most promising options available to authorities to improve the effectiveness of traffic law enforcement operations.

Executive Summary

Road accidents are a major cause of death in many countries. Estimates indicate that approximately 400,000 people die every year in road accidents around the world. Deaths and injuries caused by road accidents result in significant social and economic costs and it has been estimated that in OECD countries, approximately 1 - 2 per cent of GNP is lost every year due to road traffic accidents.

Research literature dealing with the prevention and reduction of road accidents commonly refers to three approaches, namely environment / engineering solutions, education and enforcement. The most documented of these approaches is that of enforcement which is defined as the area of activity aimed at controlling road user behaviour by preventative, persuasive and punitive measures in order to effect the safe and efficient movement of traffic.

Traffic law enforcement can be an extremely costly activity and many policing authorities have developed methods to increase the efficiency and effectiveness of enforcement operations. With this objective in mind, the Netherlands' Ministry of Transport, Public Works and Water Management commissioned the Institute for Road Safety Research (SWOV) to prepare a 'state of the art' report on road safety enforcement methods.

It was envisaged that the main focus of the report would be on the Dutch enforcement experience, however, it was decided that an international review should also be prepared to highlight new and innovative approaches to traffic law enforcement being undertaken in other countries. The Monash University Accident Research Centre, in Australia, was commissioned by SWOV to prepare such a review. Australia is internationally renowned for its efforts and achievements in the area of road safety enforcement and it was felt that the Australian experiences might prove beneficial in the preparation of the main SWOV report.


The project specification called for a review of four specific enforcement areas, namely alcohol, speed, seat belts and intersections. Road safety and enforcement organisations in Australia, Europe and North America were contacted and asked to supply relevant enforcement literature. Major international bibliographic databases were also examined. The literature search identified a large number of enforcement references and, as a result, it was necessary to focus primarily on post 1984 literature.

Approximately 800 references were finally collected and examined. Over 550 references were actually cited in the review. From this extensive literature review, conclusions and recommendations regarding the range of methods available to increase the effectiveness and efficiency of enforcement operations were detailed.


  • The success of enforcement is dependent on its ability to create a meaningful deterrent threat to road users. To achieve this, the primary focus should be on increasing surveillance levels to ensure that perceived apprehension risk is high.
    • once this has been achieved, increasing penalty severity and the quick and efficient administration of punishment can further enhance the deterrent effect.
  • Significantly increasing the actual level of enforcement activity is the most effective means of increasing the perceived risk of apprehension.
  • The use of periodic, short-term intensive enforcement operations (blitzes) is a more cost effective enforcement option, however, the effect on road user behaviour may be reduced.
  • The use of selective enforcement strategies, designed to specifically target high risk road user behaviour and traffic accident locations is another cost effective alternative.
  • Automated enforcement devices provide the most cost effective means of significantly increasing apprehension risk and should be adopted as a matter of priority.
  • The use of publicity to support enforcement operations should be adopted as a means of increasing enforcement effectiveness.
    • it is essential that road users actually observe the publicised increase in the level of enforcement activity otherwise behavioural changes are usually only short-term.
    • publicity as a stand alone measure can increase community awareness of road safety issues, however, it has only a minimal effect on actual road user behaviour.
  • If the risk of apprehension is high then the use of legal sanctions, such as licence suspension and revocation procedures, can be an effective deterrent.
  • The use of point demerit schemes provides an effective means of linking less serious repeat offences to more severe penalties.


  • The primary focus of alcohol enforcement activities should be on increasing the overall level of surveillance.
  • The introduction of per se legislation and provisions which allow police to stop and test any driver, are considered necessary to develop effective alcohol enforcement strategies.
  • the use of sustained and highly intensive random breath testing (RBT) operations is one of the most effective means of deterring drink driving behaviour.
    • to maximise the benefits of RBT operations it is essential that a large proportion of drivers are stopped and that ALL are tested for alcohol impairment.
    • RBT operations should be highly visible, accompanied by sustained high levels of publicity, rotated among numerous FIXED locations and undertaken for no longer than a one hour period at each location.
  • The strategic deployment of random breath testing operations or enforcement "blitzes" should be considered if a less resource intensive enforcement option is required.
  • The use of passive alcohol sensors is one additional means of increasing the efficiency of roadside testing operations.
  • Police commitment to RBT is essential to ensure its overall success.
    • police education programs and evaluation studies (to provide feedback) should be an important component of all RBT operations.
  • Legal sanctions are an essential element in the process of deterring drink driving behaviour and greater emphasis should be placed on the combined use of fines with licence actions, such as suspension and revocation.
  • the use of roadside licence suspensions is an effective countermeasure and provides a means of increasing the immediacy and certainty of punishment.
  • The lowering of legal blood alcohol concentration (BAC) limits for more high risk road users can be an effective means of reducing the level of alcohol related accidents.
  • The fitment of alcohol ignition interlocks, in the vehicles of recidivist drink drivers is an effective countermeasure which should be considered.
  • Publicity campaigns should always be an integral component of enforcement strategies.
  • The use of preventative strategies such as the implementation of alcohol control policies and taxation measures, the development of server intervention programs and the increased availability of public and personal breath testing devices can compliment enforcement activities and should be seriously considered.


  • The primary focus of speed enforcement should be on increasing surveillance levels, and hence the actual and the perceived risk of detection.
  • Traditional vehicle based enforcement methods should focus on increasing the visibility and unpredictability of traffic policing operations.
    • highly visible stationary enforcement operations have the greatest deterrence potential when using police vehicle deployment methods.
    • these activities should also be supported by the use of both marked (visible) and unmarked (non-visible) mobile speed enforcement operations in order to increase the unpredictability of where, how and when enforcement will be encountered.
  • Primary consideration should be given to the implementation of strategies based around the intensive use of automated speed enforcement devices.
    • to maximise the benefits and community acceptance of speed camera operations it is important that enforcement is primarily targeted at accident locations where speed is known to be a causal factor.
  • The use of new automated digital imaging systems can increasing the apprehension effectiveness of speed camera operations.
  • The use of both fixed (unmanned) and temporary site (manned) speed camera operations can maximise the system wide effectiveness of speed enforcement operations.
  • The development of strategies designed to ensure better spatial deployment of available policing resources can increase the efficiency of enforcement operations.
  • The use of publicity to support speed enforcement activities is an essential requirement to raise community awareness and improve the effectiveness of enforcement operations.
  • Reducing the size of enforcement tolerance levels on speed limits can reducing the level of speeding behaviour and ensuring greater adherence to posted speed limits.
  • Behavioural feedback strategies such as the public posting of speed information displays and incentive programs can increase the effectiveness of speed enforcement operations.
  • Greater emphasis should be placed on the use licence suspension / revocation procedures.
  • The implementation of strategies designed to target and deter repeat offenders, such as point demerit systems, should be given a high priority.
  • In order to be effective, speed limits must be perceived by road users as being appropriate for the existing road environment conditions.
    • emphasis should be placed on increasing the credibility of speed zones so as to ensure greater acceptance and adherence, by road users, to the posted speed limits.
    • the use of 'expert' systems for speed zoning classification and the use of variable speed limits are possible methods of increasing speed limit credibility.
  • Enforcement should not be relied upon as the sole means of reducing the level of speeding behaviour. Preventative strategies which target the "agents" of speeding, namely the vehicle and roadside environment should be considered as an alternative or supplementary means of reducing the level of speeding behaviour.
    • the use of speed limiting devices and measures designed to physically modify the roadside environment have considerable potential.
    • the use of perceptual speed countermeasures may also offer a low cost means of reducing the level of speeding behaviour.
    • vehicle design characteristics to improve the accident avoidance capability of vehicles, as well as the level of protection provided to vehicle occupants, can potentially reduce the injury consequences of speeding behaviour.


  • Legislation should be based on the policy of 'primary' enforcement in order to support the increased use of more active enforcement operations.
  • Consideration should be given to the use of information obtained from automated speed enforcement operations as a means of detecting seat belt offences and significantly increasing the actual and perceived risk of apprehension.
  • The simplest and most cost effective enforcement strategy is one which ensures that seat belt checks are adopted as a standard operational procedure when undertaking other forms traffic policing activities requiring roadside stopping of motorists.
  • Consideration should be given to the development and implementation of periodic, high intensity enforcement strategies ('blitzes').
  • Enforcement activities should be supported by high levels of publicity and program evaluations should be undertaken to provide police and the public with feedback.
  • Special consideration should be given to the use of police education programs to promote the safety and cost benefits associated with seat belt enforcement operations.
  • Consideration should be given to the more widespread implementation of seat belt incentive programs.
  • The use of feedback devices (seat belt warning devices and dashboard stickers) designed specifically to remind occupants to use their seat belts, should be actively promoted.


  • The primary focus of enforcement activities should be on reducing the level of deliberate red light running behaviour at signalised intersections.
  • The use of selective enforcement strategies should be considered as one possible means of improving the effectiveness and efficiency of traditional enforcement activities.
    • highly visible enforcement operations supported by sustained publicity are essential elements.
  • Primary consideration should be given to the introduction of automated red light cameras at high accident risk intersections.
  • In order to maximise both the deterrence and accident reduction effectiveness of red light cameras consideration should be given to use of:
    • warning signs at intersection approaches;
    • the use of highly visible hardware installations;
    • the rotation of a several cameras through a large number of treated intersections;
    • the use of high levels of supporting publicity; and
    • the visible deployment of the camera flash unit when cameras are not installed at treated sites.
  • The use of new digital imaging systems should be considered as they can significantly increase apprehension rates and are able to be used as a portable red light enforcement device.
  • Greater consideration should be given to intersection design considerations as a means of reducing intersection conflict situations and as an alternative to enforcement.
    • the use of appropriate intergreen timings, vehicle turning phases (for drivers wishing to turn at a right angle against the opposing flow of traffic) and active intersection warning signs should be considered.
    • the more widespread use of roundabouts (as an alternative to signalised intersections) and the provision of turning lanes at intersections should also be given a greater priority.

Sponsor: Institute for Road Safety Research (SWOV)