All over the world, road traffic crashes are responsible for a substantial share in accidental deaths. Within Europe (EU 27) some 39000 people lost their lives in road accidents in 2008 . Traffic violations such as speeding and driving while under the influence of alcohol are generally acknowledged as important contributing factors to crash risks. Hence the importance of developing effective road traffic enforcement strategies. Enforcement strategies typically consist of monitoring activities and sanctioning policies (e.g. Polinsky and Shavell, 2000). In general, the literature on enforcement has advised the use of targeting specific groups to maximize deterrence when enforcement budgets are limited (e.g. Harrington, 1988). However, targeting or state-dependent enforcement is not straightforward to implement in road traffic enforcement. It is often not possible to develop different monitoring strategies for high risk drivers and low risk drivers. As a case in point, fixed speed cameras impose the same detection probability on all passing drivers. On the other hand, for offenses such as drunk driving, it might be possible to increase monitoring probabilities for high risk drivers compared to low risk drivers by increasing the number of evening and night time inspections, especially during weekends. Thus road traffic enforcement poses its own specific challenges compared to, for example, enforcement of environmental policy (e.g. Cohen, 2000) or occupational safety enforcement (e.g. Pouliakas and Theodossiou, 2013). In this literature review, we use a formal model of non-compliance in order to structure the multitude of research papers on road traffic enforcement. Using the critical elements of an effective enforcement strategy determined in this conceptual model, we give an outline of recent research related to road safety compliance enhancement . In doing so, we provide a (partial) update of the study of Zaal (1994). Zaal (1994) provided an extensive overview of research papers related to traffic safety enforcement. More specifically, the study focused on the enforcement of alcohol-impaired motorists, of speeding motorists, of seat belt wearing and of signalized intersections. The different types of traffic enforcement methods were described and analysed in terms of efficiency and effectiveness. His main conclusion centered on the importance of educational and engineering approaches as well as publicity campaigns to complement road enforcement actions. In this contribution, we take a more limited approach than the one used by Zaal (1994): we concentrate on three types of violations (speeding, driving under influence and seat belt use) and we focus on the effectiveness of enforcement policies. In order to further structure the discussion, we categorize the relevant papers in terms of the type of policy instrument used for compliance enhancement. We illustrate the relevance of several observations by focusing on road traffic enforcement in Belgium. In section 2, we start by providing a simple conceptual framework to provide structure to the literature we discuss. In section 3, we study the relationship between road user behaviour and road safety. We concentrate on speeding, drinking and driving, and seat belt use. In section 4, we look at compliance enhancement policies such as engineering approaches, informational campaigns, regulation and enforcement. In section 5, different monitoring and sanctioning strategies are discussed in terms of their effectiveness in reducing accident risk on roads. (Author/publisher)
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