The majority of all traffic accidents are caused by human factors (Lewin, 1982; Evans, 1991 ). One of these human factors that is well known to be associated with increased accident risk is the committing of various traffic law violations (Reason et al., 1990, Parker et al. 1995; Zaidel, 2001 ). Probably the best studied and documented is the relationship between driving under the influence of alcohol and accident risk. After consuming one to two glasses of alcoholic beverages, accident risk starts to increase exponentially with every additional glass, resulting in increased risk factors of 4, 6, and 17 for BAG levels of 1, 1.3, and 1.8 g/1 respectively (Borkenstein et al., 1974; Hurst et al., 1994). Beside the increased accident risk alcohol consumption negatively influences injury severity as well. Fatality rates for drivers involved in a traffic accident with a BAG above 1.5 g/1 are reported to be up to 200 times higher than to those of sober drivers (Simpson & Mayhew, 1991 ). Speeding is another traffic violation with ample evidence of its relationship with accident risk and severity. Newtonian physics implies that higher speeds increase crash risk due to reduction of available friction, leading to risk of loss of control, reduction of time-to-collision, and crash forces increasing with the square of speed. On the basis of extensive research on the relationship between speed, speed limits, and accidents, it is estimated that, depending on the road category, a one mile per hour reduction in mean speed of traffic could produce a two to seven percentage reduction in the number of injury accidents (Nilsson, 1990; Finch et al., 1994, Taylor et al., 2000). Other researchers have pointed to the importance of speed variance: vehicles moving much slower or faster than the mean traffic speed tend to be over-represented in accident statistics (Solomon, 1964; Girillo, 1968; Hauer, 1971 ). The rule of thumb that results from various studies is: an average speed increase of 1 km/h means a three percent higher risk of an injury accident (Finch et al., 1994; Taylor et al., 2000). In severe accidents, the increase is even bigger: 1 km/h means a five percent higher risk of serious or fatal injury. The broad concept of 'traffic law enforcement' covers the entire penal procedure designed to persuade road users to obey traffic laws and regulations through the threat of detection of a violation and the imposition of a penalty. Enforcement of traffic laws is intended to influence the behaviour of road users in such a way that their risk of becoming involved in an accident, or causing an accident, decreases. 'Police enforcement' is the actual work of monitoring violations of traffic laws, apprehending offenders, and securing evidence needed for prosecution of offenders. There is good evidence that police enforcement of traffic rules promotes road safety and safe traffic behaviour, and therefore should be considered an integral part of transport management policies (Zaidel, 2002; Zaal, 1994; ETSG, 1999). Police enforcement can only be effective if it operates in a supportive environment of laws, regulations, and a sensitive penal system. These combined forces act to create the deterrence effect of police enforcement, both on the individual level and on society at large (Hakkert, 1994). In this presentation I will describe the Dutch measures and effects in the field of enforcement of drinking-and-driving. First, section 2 provides a description of the monitoring of drinking-and-driving in the Netherlands. Section 3 presents an overview regarding developments in the field of drink-driving in the Netherlands. Section 4 addresses the effort and costs necessary to achieve cost-effective levels of Random Breath Testing in the Netherlands. In section 5 recommendations are given to improve the effectiveness and efficacy of enforcement of drinking and driving.
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