from the Observatory Impact on road safety of enforcement Enforcement activities planning Surveillance method and intensity

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1 In depth 23 Third Quarter 21 from the Observatory MINISTERIO DEL INTERIOR Observatorio Nacional de Seguridad Vial Impact on road safety of enforcement 1. Introduction In all developed countries policies of enforcement play an important role in safety programs. It is estimated that in the European Union risk behaviours related to driving speed, alcohol blood level and seat belts are responsible for about 25, deaths, and that a substantial increase in the intensities of enforcement may help to significantly reduce this figure. However, necessity and effectiveness of enforcement are often controversial. The National Road Safety Observatory has conducted a review of the current state of knowledge on enforcement impact on the number of accidents and casualties. A full report of this review is available on the website of the Directorate General for Traffic ( This issue of In depth from the Observatory provides a summary of the most salient features. In order to be brief, all scientific publications and reports consulted are identified here only by the surnames of the authors and dates of publication; detailed references can be found on the full report. Specific objectives were: To identify and define objectives and main elements of an enforcement system (section 2). To discuss what risk behaviours most influence on the occurrence of accidents, and in which, therefore, should be more focused surveillance and law enforcement activities (section 3). To summarize the main estimates of the effectiveness of different enforcement methods of speed limit, driving under the influence of alcohol and safety belt use (section 4). To analyze the influence of an increased intensity of enforcement through, for example, increasing traffic police agents or controls on the driving behaviour, and the number of accidents and casualties (section 5). 2. Objectives of an enforcement system Enforcement is the activity through which effective compliance of legislation by road users is verified. This is essentially a deterrent activity, whose objective is not to increase the number of penalties, but reduce the proportion of users adopting certain risk behaviours. Figure 1 summarizes the elements of an enforcement system. The variable we want to influence is the actual degree of compliance box 6 shaded in green, which is supposed to depend on two sets of factors: 1. Personal driver characteristics, his attitude toward risk taking and knowledge of risks associated with different behaviours box 3. Information and awareness public campaigns are often intended to act on these factors, improving, for example, user knowledge of the risk that involve behaviours such as exceeding speed limit, not wearing seat belts or driving with a blood alcohol level over the maximum allowed. 2. Driver s perception of the predictable consequences of not complying with legislation. A driver feels more deterred from breaking the rules if they perceive a high probability of being under surveillance box 5, or if the economic, administrative or criminal penalties for traffic offence are severe, box 8. Enforcement activities planning Figure 1. Model of enforcement Surveillance method and intensity 7 8 Objective probability of being under surveillance Information campaign Subjective probability of being under surveillance Driver attitudes, risk awareness Degree of compliance Disciplinary proceeding Source: National Road Safety Observatory, based in part on the model proposed in the European project ESCAPE (Mäkinen and others 23). It should be noted that the relative importance of these factors depends on each driver. Some people would be willing to comply with rules even in a scenario of no surveillance. In other cases, however, it is crucial the personal impression of the consequences of a hypothetical infringement. In the centre of the figure box 5 it is emphasized the probability subjective or perceived by the driver to be under surveillance during the course of a trip. This is a basic magnitude when

2 In Depth l 23 planning any system. The following factors contribute to increasing the subjective probability (Kallberg et al, 28): Increase in the objective probability of being under surveillance box 7. While subjective probability can only be investigated through surveys, the objective probability allows more direct measures: the number of checkpoints carried out breath test, speed, seat belt use per each registered driver or vehicle. Information campaigns carried out simultaneously to enforcement campaigns box 2. Method of surveillance box 4, and in particular: Place and time of checkpoints unpredictable. Combination of different visibility policing activities (highly visible and less visible) Place and time of checkpoints concentrated where there is a high rate of infractions. Surveillance activities carried out during long periods of time. One of the main conclusions to be drawn from the previous discussion is that the effectiveness of an enforcemement system depends on several factors, which interact in a complex way. This paper pays special attention to the relationship between the intensity of enforcement or what is the same, the value of the objective probability of being under surveillance, driving behaviour and accidents. However, it should be noted that, for this relationship to work in the expected direction, all other system components must be used optimally. 3. Major risk behaviors In developed countries, laws on traffic and road safety regulate a large number of risk behaviours related to issues such as right of way, speed, alcohol consumption, illegal overtaking, restraint devices or use of lighting devices. In addition, there is a specific regulation of professional transport. To optimize the use of available resources, the enforcement shall pay particular attention to those behaviours with the highest impact on the number of accidents and casualties, with which a higher profit is expected. In this sense, speeding, drink driving, and use of seatbelts surveillance play a key role in the policies of most European countries (Mäkinen and others 23). Scientific studies have shown a clear relationship between these three behaviours and the risk of accident and injury. We summarize below some of the best evidence available: According to a recent study carried out in the United States (Blomberg et al, 29), driving with a blood alcohol level of 1. g/l, twice the maximum allowed in Spain, mean a risk of accident almost five times higher than the value corresponding to those drivers who did not drink; to 1.5 g/l, the risk is 22 times higher (see figure 2). Figure 2. Connection between blood alcohol level (g/l) and risk of being involved in a traffic accident of any severity. The risk is expressed in relation to drivers with g/l for whom is assigned the value 1 RELATIVE RISK (G/L=1) 9, 8, 7, 6, 5, 4, 3, 2, 1,,,,5 1, 1,5 2, 2,5 Source: Blomberg and others (29). BLOOD ALCOHOL LEVEL (G/L) According to Australian studies (Kloeden et al, 21 and 22), driving on inter-city roads 2 km/h faster than the average means multiplying by five the risk of being involved in a serious accident; on urban roads the same difference multiplies by 3 the risk. (see figure 3). Figure 3. Relationship between deviation from average speed (km/h) and risk of being involved in an accident with at least one casualty. The risk is expressed in relation to drivers who travel at average speed, for whom is assigned the value 1 RELATIVE RISK (AVERAGE SPEED=1) 35, 3, 25, 2, 15, 1, 5,, -15, -1, -5,, 5, 1, 15, 2, 25, DIFERENCE IN RELATION TO AVERAGE SPEED (KM/H) URBAN ROADS (LIMIT 6 KM/H) INTER-URBAN. ROADS (LIMIT 8-12 KM/H) Source: Kloeden et al (21 and 22). (Note: basically, inter-urban roads include one way conventional road.) In case of involvement in an accident, seat belt use reduces the risk of death by 45-5% in front seats and 25% in rear seats, according to a review of studies conducted by Norwegian researchers (Elvik and Vaa, 24). Available data show that the proportion of traffic offenders is highly variable between different behaviours. Thus, while drivers travelling in Europe with a blood alcohol level over the maximum allowed is estimated at 2-3% (European Transport Safety Council, 26), the proportion of drivers exceeding speed limits reaches typical values of 4-5% (OECD, European Conference of Ministers of Transport, 26).

3 All previous evidences refer to individual risk experienced by an average driver. The sense of the conclusions is the same when considering aggregate variables referred to road users as a whole. In a report published in 1999, the European Transport Safety Council indicated that the elimination of all infractions could halve the number of traffic accidents in Europe. For its part, the impact assessment of the proposal of a Directive to facilitate cross-border enforcement of road safety legislation (European Commission, 28), which includes estimates for 24, states that 3% of road fatalities in the European Union are due to speeding, 25% to drink driving and 17% for not wearing seat belts. As a whole, it is estimated that 25, deaths in the EU are caused by these behaviours (calculated on approximately 47. deaths of 27 Members States in 24). To reach this figure, it has been taken into account that in the same accident may come together several infractions. It is estimated that if the enforcement level average was be multiplied by 2, it could prevent 2% of these 25, deaths, with a benefit-cost ratio of Effectiveness of different methods of enforcement The effectiveness of the different control methods has previously been the subject of a large number of investigations. In general, these studies have estimated the impact caused when implementing a completely new method of control -for example, fixed radars to speed enforcement -or implement a program which, although not involving a new control method, means a significant increase in intensity of surveillance in relation to the initial situation, for example, alcohol or seatbelt temporary enforcement campaigns. We must take into account that many evaluation studies do not provide quantitative information on the surveillance levels carried out. This is the reason why this section only analyzes the relationship between surveillance method and accident frequency. The impact of increasing or decreasing the intensity of enforcement is considered below. It has been used as a source of information the results of the meta-analysis studies conducted in the framework of the PEP PER (Police Enforcement Policy and Programmes on European Roads), funded by the European Union (Erke and others, 28). Meta-analysis is a statistical technique for summarizing quantitatively, in a mean estimate, the results of all scientific work in a particular research field. For example, when in the next section we say that fixed speed cameras reduce the number of fatal accidents by 39%, it should be interpreted as follows: if you weigh the results of all investigations that have analyzed the impact of fixed cameras, which meet certain methodological criteria, you get a mean value of 39%. All estimates quoted below refer to the effect on accidents in which sections and roads have been taken surveillances activities, such as sections where fixed speed cameras are installed, or roads where breath test are randomly taking place. 4.1 Speed enforcement There are three types of speed enforcement methods. Stationary speed enforcement The speed measurement is carried out by police units, visible or hidden on the side of the roads. A second police unit, located further forward, stops drivers travelling over the limit when they receive the message of traffic offence. Mobile speed enforcement Mobile patrols carry out surveillance on vehicles, camouflaged or identified, while moving along the flow of traffic. With the same staff, this method allows to extend surveillance in time and space, although sometimes at the expense of not achieving high surveillance intensity at any point in the network. Automatic speed enforcement In these methods, unlike stationary speed enforcement, registration and notification of the traffic offence is conducted automatically or semi-automatic, using automatic speed surveillance cameras which take photographs of the vehicles and reading the plate numbers. We distinguish two basic procedures: Fixed speed cameras: located on gantries or poles, at fixed points in the network, usually marked. Mobile speed cameras, located at variable points, and generally less visible or even hidden. In PEPPER project the average effectiveness of these methods of surveillance was evaluated, based on analysis of 45 scientific researches. Results are summarized in table 1. Table 1. Mean estimates of the effect on accidents depending on methods of speed surveillance Method of surveillance Percentage change in the number of accidents, and confidence interval 95% All accidents Fatal accidents Stationary speed limit enforcement -11% (-22%; +1%) -27% (-45%; -2%) Mobile speed limit enforcement -6% (-16%; +4%) -12% (-35%; +18%) Automatic speed enforcement: all types -3% (-38%; -23%) -33% (-39%; -27%) Automatic speed enforcement: fixed speed cameras -34% (-42%; -25%) -39% (-5%; -25%) Automatic speed enforcement: mobile speed cameras -17% (-34%; +4%) -32% (-39%; -24%) Combination of methods -18% (-33%; +1%) -16% (-36%; +11%) Source: Project PEPPER (Erke and others, 28). We can see from the table 1 that there are significant variations between methods. Automatic speed enforcement using fixed cameras is the most effective method for reducing accidents until 34-39%. The lowest reductions are shown on the mobile speed enforcement. Comparisons between methods should be performed, in any case, with caution, because there may be important differences both between the typical intensities achievable with different surveillance methods and between the sizes of the areas considered.

4 In Depth l 23 The fact of obtaining, in general, estimates of greater effectiveness in fatal accidents is consistent with the expected decline in the average severity of accidents as a result of slowing speed. 4.2 Drink driving enforcement In PEPPER project (Erke and others, 28), were analyzed 4 studies of effectiveness of conducting breath tests by police stationary teams situated at the road side. The average reduction observed in the number of accidents was 15%. 4.3 Safety belt use enforcement On average, use of seat belts enforcement campaigns are responsible for an increased rate of use 21% during the campaign period, and 15% after ending (project PEPPER: Erke and others, 28). These results are based on analysis of 18 studies, and refer mainly to experiments in which the police surveillance is combined with publicity campaigns in the media, pamphlets and information booklets, or incentives. The duration of campaigns is highly variable from one experience to others. 5. Relationship between enforcement intensity, driving behavior and safety The theoretical relationship between enforcemente intensity number of checkpoints, hours of police activity and the percentage of traffic offenders has been analyzed by several researchers (eg, Elliott and Broughton, 25). Let s suppose that, based on a hypothetical situation of no surveillance, intensity is gradually increased, we can expect the following three phases: Phase 1: Surveillance intensity is so low that the probability of surveillance perceived by drivers is virtually nil. Therefore, the percentage of traffic offenders is not affected. Phase 2: Intensity reaches the minimum necessary to effectively influence driving behaviour. From this minimum, any increase in intensity is accompanied by a decrease in the percentage of traffic offenders. Phase 3: If intensity increases enough, we reach ideally a situation of zero traffic offenders. Several scientific papers have analyzed the validity of this theoretical relationship. For example, Dutch researchers (De Waard and Rooijers, 1994), from an experiment based on speed surveillance showed that, once exceeded a minimum intensity threshold, both mean and dispersion of velocities decreased when increasing the number of reported drivers. In the framework of the European project SUNFLOWER (Koornstra and others, 22), the effect of the surveillance on behaviour was analyzed with various indicators related to seat belt use and alcohol consumption in the UK, Sweden and the Netherlands. The main results, shown in figure 4, prove that countries with the lowest percentage of traffic offenders are those with higher intensity of reports and checkpoints. Figure 4 Left: relationship between the percentage of drivers not using seat belts and the number of reports for not using seat belt per registered driver. Right: relationship between the percentages of drivers killed with a blood alcohol level exceeding 1 g/l and the number of breath tests per registered driver. Holland, Sweden and Great Britain. 2 25,% 25,% Holland Great Britain PERCENTAGE OF DRIVER NOT WEARING SEAT BELT 2,% 15,% 1,% 5,% Sweden Great Britain PERCENTAGE OF DRIVERS OVER 1g/l 2,% 15,% 1,% 5,% Holland Sweden,% 1/5 1/25 3/5 1/125 1/1 NUMBER OF REPORTS FOR NOT WEARING SEAT BELT PER REGISTERED DRIVER,% 1/2 1/1 3/2 1/5 1/4 3/1 NUMBER OF BREATH TEST PER REGISTERED DRIVER Source: Project SUNFLOWER (Koornstra and others, 22). Other relevant international research is the European project ESCAPE (Traffic Enforcement in Europe: effects, measures, needs and future), which conducted a review of 8 studies on the relationship between surveillance intensity, speed and accidents (Elvik, 21). In 6 of these studies, the relationship between variables was as expected: increased enforcement produced a positive effect on safety, measured by average speed or frequency of accidents. The remaining 2 studies found an inverse relationship, although the ESCAPE report suggests that their results may have been due to methodological shortcomings. In Spain, the recent year s trends are consistent with the previous discussion. In 29 approximately 26.5 million speed checkpoints were conducted by the Traffic Division of the Civil Guard excluding fixed speed cameras, representing an increase of more than 1 million in relation to 23. In the same period, the rate of reported vehicles decreased from 3.23 to 2.91% (see Figure 5). Moreover, while the number of preventive breath tests increased by a factor of 3 from 1.7 to 5.1 million, the positive rate decreased from 4.18 to 1.77% (see figure 6).

5 Figure 5. Evolution of speed controls carried out by the Traffic Division of the Civil Guard and percentage of vehicles reported. Excluding fixed speed cameras. Years Figure 6. Evolution of breath tests in preventive speed limit enforcement by the Traffic Division of the Civil Guard and percentage of positive breath tests. Years ,5% 6.. TEST IN PREVENTIVE CHECKPOINTS 4,5% ,% 2,5% % POSITIVE CHECKS 4,% 3,5% 3,% CHECKED VEHICLES REPORTED VEHICLES ,% 1,5% 1,%,5%,% ,5% 2,% 1,5% 1,%,5%,% Source: Directorate General of Transport, National Road Safety Observatory. Source: Directorate General of Transport, National Road Safety Observatory. The positive trend in driving behaviour, showed in the two previous figures as percentage of vehicles and drivers reported after being checked, is also evident when analyzing other indicators available in our country. Table 2 shows the evolution of various indicators of safety belt use, alcohol consumption and speed in In all cases clear improvements may be observed. Table 2. Evolution of different driving behaviour indicators in the period INDICATOR SOURCE VALUE IN 23 VALUE IN 29 Percentage of safety belt use. Front seats. Percentage of safety belt use. Rear seats. Percentage of drivers killed with a blood alcohol level higher or equal to.3 g/l. Percentage of light vehicles (private cars, vans) travelling faster than 12 km/h on motorways. Percentage of light vehicles (private cars, vans) travelling faster than 1 km/h on conventional roads. National Road Safety Observatory Nacional Road Safety Observatory 87% (Inter-city ) 61% (Urban) 43% (Inter-city) 34% (Urban) 97% (Inter..city) 87% (Urban) 82% (Intercity) 62% (Urban) National Institute of Toxicology 37.4% 3.% Ministry of Public Works (source: State Road Network) Ministry of Public Works (source: State Road Network) 28.% 18.9% (in 28) 17.4% 9.5% (in 28) Trend of number of reports is shown in figure 7. We can see from the graph a clear increase in 27 and 28, mainly due to an increased number of reports carry out by automated speed cameras. However, the improvement of driving behaviour makes such increase in reports to be proportionately lower than traffic law enforcement patrols. In the period considered, 23-29, the number of fatalities has decreased by 49.7% (see again figure 7). REPORTS Figure 7. Trend of the number of reports and fatalities. Years (excluding Basque Country and Catalonia) REPORTS FATALITIES Source: Directorate General for Traffic, National Road Safety Observatory. FATALITIES The evolution of fatalities and injuries may be reflecting in part the impact of other measures adopted in the last few years which were in force at the same time than the increased intensity of enforcement, as the penalty point system or the Penal Code reform. If we want to separate, as accurately as possible, the influence of increasing law enforcement over road traffic it is necessary to use statistical models to estimate simultaneously the impact of several variables. In Spain, the most important effort undertaken in this area of research is the model DRAG-Spain, conducted by a research team from the Polytechnic University of Madrid and commissioned by the Directorate General for Traffic (INSIA-UPM, 29). In this model, the temporary evolution of the number of accidents on inter-urban roads is explained from a great number of factors related to mobility, infrastructure, weather, drivers, economical conditions, car fleet, speed, enforcement and legislation. According to the results of this model (see figure 8), during the period , each 1% increase in the number of agents of the Civil Guard was accompanied by a reduction of 3.59% of the number of fatalities, when we consider the period 25-27, the corresponding reduction was 8.27%. The difference between these two results suggests the existence of a structural change in the last few years, under which the same increase in enforcement seems to have a more positive effect on safety.

6 MINISTERIO DEL INTERIOR Observatorio Nacional de Seguridad Vial Observatorio Nacional de Seguridad Vial Josefa Valcárcel, Madrid D.L.: M-XXXXX-21 Nipo: Also, an increase of surveillance on driving under the influence of alcohol is associated with an improved safety: again according to the results of DRAG-Spain model, each 1% increase in the number of preventive controls result in is a reduction of fatal accidents between 1.31 and 1.38%. Figure 8. Expected variation (in %) in the number of fatalities as a result of an increase of surveillance intensity. Model results DRAG-Spain EXPECTED VARIATION (IN %) IN THE NUMBER OF FATALITIES AS A RESULT OF AN INCREASE OF SURVEILLANCE INTENSITY - 8,27% - 3,59% -1,38% -1,31% - 1,% - 8,% - 6,% - 4,% - 2,%,% DRAG MODEL Source: INSIA-UPM, Conclusions DRAG MODEL INCREASE 1% IN THE NUMBER OF RANDOM BREATH TESTS INCREASE 1% IN THE NUMBER OF TRAFFIC AGENTS This paper has presented an overview of current knowledge on the relationship between traffic law enforcement and safety. Main conclusions of this paper can be summarized as follows: An enforcement system is composed of different elements, coordinated and used to increase the perceived likelihood of drivers being punished if they don t comply with the current regulation. This is essentially a deterrent activity, whose objective is not to increase the number of penalties, but reduce the proportion of users who adopt certain risk behaviours. Increases in speed, driving under the influence of alcohol and not wearing seat belts are significantly associated with an increased risk of accidents. If all others factors of influence remain constant, any policy that is effective in reducing these behaviours should have beneficial effects on the frequency of accidents and casualties. The effectiveness of the several methods of surveillance has been demonstrated in a large number of scientific studies. The average effects found in international studies can be summarized as follows: Speed enforcement reduces the number of fatal accidents by 12-39%, depending on the method of surveillance. Police enforcement of driving under the influence of alcohol is associated with a reduction of 15% of accidents. Action to boost the wearing of seat belts influence significantly on utilization rates. It has been observed a mean increase of 21% while carrying out operations, and 15% after ending. Most of the studies that have analyzed the influence on safety of the several intensities of enforcement support the hypothesis that once passed a minimum level of enforcement under which the driving behaviour is not affected, a higher intensity produces a reduction in traffic offences and accident frequency. The final report of the European project ESCAPE sums it up as follow: there is considerable evidence that subs tantial changes in the extent of police enforcement are correlated to changes in the number or severity of traffic accidents; more enforcement is associated with fewer accidents (Mäkinen and others 23, p. 16). A review of evidence conducted by the British laboratory TRL concluded that the great majority of the studies in the literature have found that increasing the level of traffic policing reduces the number of road accidents and traffic violations (Elliott and Broughton, 25, p.1). Finally, the final report of the European project PEPPER says that evidences seems compelling that massive speed control and continuos drink-driving control can have a decisive role in bringing down road fatalities substantially and relatively quickly. In Spain, there has been a significant increase in the intensity of enforcement in the period 23-29, for example, the number of speed controls carried out by the Traffic Division of the Civil Guard increased by more than 1 million, and the number of preventive breath test was multiplied by a factor of 3. In the same period all indicators of driving behaviour show a favourable trend, some notable examples are: The percentage of vehicles reported in speed checks by Traffic Division of the Civil Guard decreased from 3.2% to 2.9%. The percentage of light vehicles travelling at over 12 km/h on dual carriageways was reduced by 1 points; on conventional roads, the percentage of vehicles travelling over 1 km/h was reduced by eight points. The positive results in preventive breath test decreased from 4.2 to 1.8%. Percentage of drivers killed with a blood alcohol level equal or over.3 g/l decreased from 37 to 3%. Seat belt use rate increased in both inter-urban roads and urban areas. In rear seats the increase has been close to 1%. Such improvement of driving behaviour has significantly contributed to 49.7% reduction in the number of fatalities in Results of the econometric model DRAG-Spain suggest that each 1% increase in the number of traffic agents produce between 3.6 and 8.3% reductions in the number of fatalities. According to the same work, a 1% increase in the number of preventive breath test reduces approximately 1.3% fatal accidents. In the near future, it is expected to increase the use of socalled self-enforcement and self-control methods, such as speed limiters or interlock devices if the driver exceeds the permitted alcohol blood level or any occupant don t wear seat belt. These systems can have a substantial impact on the role of traffic offences in the occurrence of accidents.