Original article
Did Chile’s traffic law reform push police enforcement? Understanding Chile’s traffic fatalities and injuries reduction José Ignacio Nazif-Munoz,1 Amélie Quesnel-Vallée,2 Axel van den Berg1 1
Department of Sociology, McGill University, Montreal, Canada 2 IRIS Lab, Department of Epidemiology, Biostatistics and Occupational Health, Department of Sociology, McGill University, Montreal, Canada Correspondence to José Ignacio Nazif-Munoz, Room 328, Peterson Hall, 3460 McTavish Street, Montreal, Quebec, Canada H3A 0E6; Jose.nazifmunoz@ mail.mcgill.ca Received 2 July 2014 Revised 4 November 2014 Accepted 10 November 2014 Published Online First 28 November 2014
ABSTRACT Background The objective of the current study is to determine to what extent the reduction of Chile’s traffic fatalities and injuries during 2000–2012 was related to the police traffic enforcement increment registered after the introduction of its 2005 traffic law reform. Methods A unique dataset with assembled information from public institutions and analyses based on ordinary least square and robust random effects models was carried out. Dependent variables were traffic fatality and severe injury rates per population and vehicle fleet. Independent variables were: (1) presence of new national traffic law; (2) police officers per population; (3) number of traffic tickets per police officer; and (4) interaction effect of number of traffic tickets per police officer with traffic law reform. Oil prices, alcohol consumption, proportion of male population 15–24 years old, unemployment, road infrastructure investment, years’ effects and regions’ effects represented control variables. Results Empirical estimates from instrumental variables suggest that the enactment of the traffic law reform in interaction with number of traffic tickets per police officer is significantly associated with a decrease of 8% in traffic fatalities and 7% in severe injuries. Piecewise regression model results for the 2007–2012 period suggest that police traffic enforcement reduced traffic fatalities by 59% and severe injuries by 37%. Conclusions Findings suggest that traffic law reforms in order to have an effect on both traffic fatality and injury rates reduction require changes in police enforcement practices. Last, this case also illustrates how the diffusion of successful road safety practices globally promoted by WHO and World Bank can be an important influence for enhancing national road safety practices.
INTRODUCTION
To cite: Nazif-Munoz JI, Quesnel-Vallée A, van den Berg A. Inj Prev 2015;21:159–165.
In 2004, WHO along with the World Bank (WB) launched the ‘World report on road traffic injury prevention’1 and globally promoted several road safety measures to tackle the roots of road crashes and avoid their tragic consequences. After 12 years of parliamentary and governmental debate, and following closely the recommendations set by the ‘World Report’ in 2005, Chile approved a comprehensive traffic law reform which via decree regulation was enacted at the end of 2006 (Urzúa J, personal communication). This reform included measures such as: (i) mandatory seat belt use for all vehicle occupants, (ii) introduction of child restraints, (iii) day-running lights for motorcycles, (iv) banning the use of cell phone while driving, (v)
stricter requirements to obtain driver licenses to drive light vehicles and (vi) higher fines for driving under the influence of alcohol.2 Statistics indicate that traffic fatality and severe injury rates per 100 000 population declined by 13% and 5%, respectively, between 2006 and 2012. However, the role of Chile’s traffic law reform—and by extension, those of the recommendations set by WHO and the WB—in this downward trend remains unknown. While a vast literature suggests that road traffic legislation reforms per se may help to prevent the occurrence of traffic crashes and its consequences,3–10 others have argued that this type of measure is ultimately sterile or at best shortlived.11 12 The latter has been particularly noticeable in Latin American countries since in many cases they lack the necessary resources to implement legislative changes.13–15 However, other literature focus on institutional mechanisms16 17 which offer more precise explanations of the potential impact of legal reform. These studies have argued that road safety legislation reforms can only be effective in reducing crashes and traffic fatalities when they are followed up with particular types of institutional mechanisms, such as police enforcement (ie, stationary or patrolling18 19) or the creation of road safety agencies,1 as well as with the introduction of technological devices, such as red-light cameras,20–22 and automatic speed enforcement,23 24 youth-focused intervention programmes25 and/or diffusion of public campaigns.26–28 In this paper, we contribute to this body of research by using Chilean data between 2000 and 2012 to empirically assess the effects of (a) traffic law reform, (b) police officers per capita, (c) police traffic enforcement and (d) the interaction of traffic law reform with police traffic enforcement on traffic and morbidity rates. Such an assessment is evidently highly relevant for Chile as a policy impact evaluation, but it also has both theoretical and methodological implications for the field of study at large. First, unlike other federal countries such as Brazil, Canada or the USA, where traffic reforms may have not been universal, Chile, as a centralised country, provides an opportunity to examine an entire national jurisdiction unit over time. The latter therefore can be regarded as a ‘natural policy experiment’.29 Furthermore, it is worth noting that under Chile’s administrative regime, in which a single national police body is responsible for patrolling traffic, coordination of enforcement should be less problematic and therefore a traffic law reform might uniformly intensify it. Second, as noted by Elvik et al,6 while there is a
Nazif-Munoz JI, et al. Inj Prev 2015;21:159–165. doi:10.1136/injuryprev-2014-041358
159
Original article significant amount of research on the efficacy of road traffic legislation reforms and the institutional mechanisms associated with them in the USA, the Commonwealth and European countries, there remains a remarkable paucity of similar research exploiting cross-jurisdictional time-series variation in other regions of the world, and particularly in South America. Third, this case offers an explicit test of national pathways through which the influence of global forces such as the policy diffusion of the ‘World Report’ can ultimately contribute to changes in national territories can play out.30 Last, from a methodological point of view, the rich cross-region time-series data available for Chile allow us to control for the impact of unobserved region and/or time-specific determinants of traffic incidents such as climate variation with the help of random effects models.31 Indeed, Chile comprises a wide range of weather conditions extending across 38° in latitude. Simple ordinary least square (OLS) estimates of the impact of traffic reform, police officers per capita or police traffic enforcement might be otherwise confounded with unobserved determinants of traffic crashes such as climate variation within regions during 2000–2012. Hence, using Chilean data permits us to evaluate the robustness of the literature of road safety institutional mechanisms, expand our road safety knowledge of the South American region more generally and of this country more particularly, and contribute to our understanding of how, in the realm of road safety policies, global factors impact national territories.
Research question Figure 1 shows a steady decline in Chilean traffic fatality and severe injury rates ( per 10 000 vehicles) between 2000 and 2012. Specifically, traffic fatalities have dropped by roughly 52% ((7.97–3.83)/7.97) and severe injuries by 56% ((38.01– 16.53)/38.01). This figure also shows a less pronounced decline in traffic fatality ( per 100 000 population) and severe injury rates ( per 10 000 population). Particularly, traffic fatalities under this indicator dropped by approximately 21% ((11.02– 8.75)/11.02) and severe injuries by 28% ((5.25–3.77)/5.25). Table 1 documents cross-regional variation in traffic fatality and serious injury rates in 2000 and 2012, the two end-year sample points for both rates: vehicle fleet and population. These numbers suggest significant cross-regional variation in fatality and severe injury rates in the year 2000. In 2000, five regions, O’Higgins, Maule, Biobío, La Araucanía and Los Lagos, had an average of 12.1 traffic fatality rates per 10 000 vehicles, while, with the clear exception of the Magallanes region, all the other regions had an average of 6.81. A very similar pattern is observed in fatalities per 100 000 population. We observe the Magallanes region to be the exception with the lowest rate of 4.56. On the other hand, O’Higgins, Maule, Biobío, La Araucanía, Los Lagos and Atacama had an average of 14.4, and all the other regions an average of 9.49. Regarding severe injury rates for the same year, we observe that Atacama, Coquimbo, Biobío, La Araucanía, Los Lagos and Aysén had an average of 46.18 per 10 000 vehicles, whereas the group composed of Tarapacá, Antofagasta, Valparaíso, O’Higgins, Maule and the Metropolitan region had an average of 34.80. For this particular rate as well Magallanes has a very low rate of 24.40. When we analyse the severity rate per population, Atacama is the region with the highest rate with an average of 79.17, Los Lagos region had the lowest rate with 44.27 and all the other regions had an average of 53.4. The first four columns for the year 2012 indicate that variation between and within regions has decreased overall. Thus, the regional data point to overall decreases in traffic fatality and severe injury in both vehicles and population rates, 160
Table 1 Variation in fatalities, serious injuries and crashes, 2000–2012
Regions 2000 Tarapacá* Antofagasta Atacama Coquimbo Valparaíso O’Higgins Maule Biobío La Araucanía Los Lagos† Aysén Magallanes Metropolitana 2012 Tarapacá* Antofagasta Atacama Coquimbo Valparaíso O’Higgins Maule Biobío La Araucanía Los Lagos† Aysén Magallanes Metropolitana
Fatalities per 10 000 vehicles
Fatalities per 100 000 population
Severe injuries per 10 000 vehicles
4.99 7.73 8.85 7.35 6.92 11.52 11.06 13.82 14.13 12.07 6.42 1.90 5.46
9.35 12.25 13.45 8.45 10.37 16.96 14.81 15.10 15.00 12.54 8.53 4.56 8.01
29.82 35.80 52.10 43.98 36.99 32.85 37.63 46.09 49.83 42.61 42.52 24.44 35.68
55.89 56.74 79.17 50.56 55.43 48.37 50.38 50.36 52.91 44.27 56.53 58.71 52.37
5.60 5.70 4.40 4.65 3.13 5.56 4.88 5.84 5.88 5.47 2.74 2.77 2.29
16.46 14.96 12.64 10.14 6.88 13.55 12.90 11.76 9.83 10.09 8.4 9.3 5.3
17.79 15.62 18.96 16.91 18.90 15.96 14.49 29.14 25.77 21.03 9.43 15.88 11.91
49.77 40.97 54.46 36.93 41.55 38.88 38.30 58.71 43.08 37.13 29.03 53.86 27.58
Severe injuries per 100 000 population
*Includes Arica and Parinacota territories. †Includes Los Rios territory.
and a convergence across regions. One potential explanation for these parallel trends could lie in the enactment of a comprehensive traffic law reform in 2006, which may have impacted police traffic enforcement. However, as we can observe in figure 1, a decreasing tendency was evident before the enactment of this law, particularly for fatalities per 10 000 vehicles and severe injuries per 1000 vehicles. There are other elements that, as noted in the literature, should be considered since traffic laws changes might be confounded with other significant factors or not strong enough to influence variation in these rates. For instance, several studies have indicated that increasing oil prices,32 33 alcohol prices,34 35 infrastructure development6 36 or unemployment37 38 can also help produce a downwards tendency. Furthermore, a more direct pathway might also be found in changes in police enforcement practices, particularly in the Chilean context where the centralised nature of this state ensures that these practices are uniformly applied across regions.
METHODS Data Outcome variables Data on (i) traffic fatalities and (ii) severe injuries were obtained from Chile’s National Commission of Road Safety of the Ministry of Transport. This organisation has compiled, from Nazif-Munoz JI, et al. Inj Prev 2015;21:159–165. doi:10.1136/injuryprev-2014-041358
Original article
Figure 1 Traffic fatalities per 10 000 vehicles and 100 000 population and severe injuries per 1000 vehicles and 10 000 population, 2000–2012. police reports, an extensive dataset of traffic fatalities and injuries in Chile from 1972 to the present. Complete data for all 13 regions are available from 2000 to 2012. This provides us with a balanced sample with N=169 region-year observations. Fatalities are classified according to status (driver, passenger, motorcyclist, bicyclist and pedestrian), age, sex and time and day of accident. Following the Chilean Penal Code, police officers classify injuries as severe (ie, injury which prevents the person from performing acts, which constitute such person’s usual and customary daily activities, at least 30 days or more immediately following the occurrence of the injury), less severe (injury which prevents the individual from returning to previous activities up until 30 days immediately following the occurrence of the injury) and minor (injury which does not require immediate medical attention). Data on vehicle fleet and population were both obtained from the National Institute of Statistics. Traffic fatalities and serious injuries per 10 000 vehicles and per 100 000 population were the outcome variables assessed in this study, for a total of four dependent variables. By analysing these variables separately, we may be able to identify the specific impact of each policy in similar, but not identical, outcomes. Last, by introducing the two denominators (vehicle fleet and population), we facilitate international comparisons of the results as well as test robustness across models.
Independent variables ‘Traffic law reform’ was coded as a yearly dummy variable, ‘0’ being the 2000–2005 period when the law had not been approved, and ‘1’ being the 2006–2012 period when the reform was in force. ‘Police per 100 000 population’ is the national number of police officers, using data from United Nations Office on Drugs and Crime. ‘Police traffic enforcement’ is measured as the number of traffic tickets processed by local courts, using data provided by the Ministry of Justice, divided by the national number of police officers, using data from United Nations Office on Drugs and Crime. It must be noted that due to security reasons, the Chilean Police Force (Carabineros de Chile) only provides information regarding the number of police officers at the national level. Thus, the operationalisation of ‘Police traffic Nazif-Munoz JI, et al. Inj Prev 2015;21:159–165. doi:10.1136/injuryprev-2014-041358
enforcement’ is number of tickets per region and year divided by the national number of police officers per year. While the literature suggests number of police officers9 39 or number of traffic tickets40 as separate proxies of police traffic enforcement, we actually propose a combination of these two factors to capture more accurately this road safety measure. First, since police officers have duties other than patrolling traffic, we recognise that an increase in the number of police officers cannot be assumed to automatically lead to a commensurate increase in traffic ticketing. Second, because significant changes in the total number of police officers can actually trigger any absolute increase in the number
Table 2
Summary statistics, 2000–2012 Observations
Dependent variables Traffic fatalities per vehicle Traffic severe injuries per vehicle Traffic fatalities per population Traffic severe injuries per population Independent variables Traffic law reform Police officers per 100 000 population Police traffic enforcement Controls Road infrastructure investment Oil price average Alcohol consumption Percentage of young male population Unemployment
Mean
SD
Min
Max
169
4.182
0.430
2.944
4.950
169
5.821
1.010
3.433
8.085
169
2.423
0.314
1.518
3.125
169
3.843
0.203
3.166
4.371
169
0.538
0.5
0
1
169
5.496
1.183
2.903
8.529
169
17.035
1.092
12.651
19.372
169 169 169
6.244 4.203 11.646
0.261 0.116 1.084
5.694 3.814 9.029
6.667 4.365 14.007
169
−2.559
0.342
−3.756
−1.897
161
162
(0.027) (1.305) (0.228)** (0.097)** (0.104) 0.000 0.871 0.465 0.193 0.032 Yes Yes 0.56 (0.031) (1.177) (0.237) (0.217) (0.070) 0.000 0.871 0.465 0.193 0.032 Yes Yes 0.46 169 (0.027) (1.205) (0.243) (0.076)*** (0.101) (0.031) (1.176) (0.237) (0.217) (0.070)
**p
Did Chile’s traffic law reform push police enforcement? Understanding Chile’s traffic fatalities and injuries reduction José Ignacio Nazif-Munoz,1 Amélie Quesnel-Vallée,2 Axel van den Berg1 1
Department of Sociology, McGill University, Montreal, Canada 2 IRIS Lab, Department of Epidemiology, Biostatistics and Occupational Health, Department of Sociology, McGill University, Montreal, Canada Correspondence to José Ignacio Nazif-Munoz, Room 328, Peterson Hall, 3460 McTavish Street, Montreal, Quebec, Canada H3A 0E6; Jose.nazifmunoz@ mail.mcgill.ca Received 2 July 2014 Revised 4 November 2014 Accepted 10 November 2014 Published Online First 28 November 2014
ABSTRACT Background The objective of the current study is to determine to what extent the reduction of Chile’s traffic fatalities and injuries during 2000–2012 was related to the police traffic enforcement increment registered after the introduction of its 2005 traffic law reform. Methods A unique dataset with assembled information from public institutions and analyses based on ordinary least square and robust random effects models was carried out. Dependent variables were traffic fatality and severe injury rates per population and vehicle fleet. Independent variables were: (1) presence of new national traffic law; (2) police officers per population; (3) number of traffic tickets per police officer; and (4) interaction effect of number of traffic tickets per police officer with traffic law reform. Oil prices, alcohol consumption, proportion of male population 15–24 years old, unemployment, road infrastructure investment, years’ effects and regions’ effects represented control variables. Results Empirical estimates from instrumental variables suggest that the enactment of the traffic law reform in interaction with number of traffic tickets per police officer is significantly associated with a decrease of 8% in traffic fatalities and 7% in severe injuries. Piecewise regression model results for the 2007–2012 period suggest that police traffic enforcement reduced traffic fatalities by 59% and severe injuries by 37%. Conclusions Findings suggest that traffic law reforms in order to have an effect on both traffic fatality and injury rates reduction require changes in police enforcement practices. Last, this case also illustrates how the diffusion of successful road safety practices globally promoted by WHO and World Bank can be an important influence for enhancing national road safety practices.
INTRODUCTION
To cite: Nazif-Munoz JI, Quesnel-Vallée A, van den Berg A. Inj Prev 2015;21:159–165.
In 2004, WHO along with the World Bank (WB) launched the ‘World report on road traffic injury prevention’1 and globally promoted several road safety measures to tackle the roots of road crashes and avoid their tragic consequences. After 12 years of parliamentary and governmental debate, and following closely the recommendations set by the ‘World Report’ in 2005, Chile approved a comprehensive traffic law reform which via decree regulation was enacted at the end of 2006 (Urzúa J, personal communication). This reform included measures such as: (i) mandatory seat belt use for all vehicle occupants, (ii) introduction of child restraints, (iii) day-running lights for motorcycles, (iv) banning the use of cell phone while driving, (v)
stricter requirements to obtain driver licenses to drive light vehicles and (vi) higher fines for driving under the influence of alcohol.2 Statistics indicate that traffic fatality and severe injury rates per 100 000 population declined by 13% and 5%, respectively, between 2006 and 2012. However, the role of Chile’s traffic law reform—and by extension, those of the recommendations set by WHO and the WB—in this downward trend remains unknown. While a vast literature suggests that road traffic legislation reforms per se may help to prevent the occurrence of traffic crashes and its consequences,3–10 others have argued that this type of measure is ultimately sterile or at best shortlived.11 12 The latter has been particularly noticeable in Latin American countries since in many cases they lack the necessary resources to implement legislative changes.13–15 However, other literature focus on institutional mechanisms16 17 which offer more precise explanations of the potential impact of legal reform. These studies have argued that road safety legislation reforms can only be effective in reducing crashes and traffic fatalities when they are followed up with particular types of institutional mechanisms, such as police enforcement (ie, stationary or patrolling18 19) or the creation of road safety agencies,1 as well as with the introduction of technological devices, such as red-light cameras,20–22 and automatic speed enforcement,23 24 youth-focused intervention programmes25 and/or diffusion of public campaigns.26–28 In this paper, we contribute to this body of research by using Chilean data between 2000 and 2012 to empirically assess the effects of (a) traffic law reform, (b) police officers per capita, (c) police traffic enforcement and (d) the interaction of traffic law reform with police traffic enforcement on traffic and morbidity rates. Such an assessment is evidently highly relevant for Chile as a policy impact evaluation, but it also has both theoretical and methodological implications for the field of study at large. First, unlike other federal countries such as Brazil, Canada or the USA, where traffic reforms may have not been universal, Chile, as a centralised country, provides an opportunity to examine an entire national jurisdiction unit over time. The latter therefore can be regarded as a ‘natural policy experiment’.29 Furthermore, it is worth noting that under Chile’s administrative regime, in which a single national police body is responsible for patrolling traffic, coordination of enforcement should be less problematic and therefore a traffic law reform might uniformly intensify it. Second, as noted by Elvik et al,6 while there is a
Nazif-Munoz JI, et al. Inj Prev 2015;21:159–165. doi:10.1136/injuryprev-2014-041358
159
Original article significant amount of research on the efficacy of road traffic legislation reforms and the institutional mechanisms associated with them in the USA, the Commonwealth and European countries, there remains a remarkable paucity of similar research exploiting cross-jurisdictional time-series variation in other regions of the world, and particularly in South America. Third, this case offers an explicit test of national pathways through which the influence of global forces such as the policy diffusion of the ‘World Report’ can ultimately contribute to changes in national territories can play out.30 Last, from a methodological point of view, the rich cross-region time-series data available for Chile allow us to control for the impact of unobserved region and/or time-specific determinants of traffic incidents such as climate variation with the help of random effects models.31 Indeed, Chile comprises a wide range of weather conditions extending across 38° in latitude. Simple ordinary least square (OLS) estimates of the impact of traffic reform, police officers per capita or police traffic enforcement might be otherwise confounded with unobserved determinants of traffic crashes such as climate variation within regions during 2000–2012. Hence, using Chilean data permits us to evaluate the robustness of the literature of road safety institutional mechanisms, expand our road safety knowledge of the South American region more generally and of this country more particularly, and contribute to our understanding of how, in the realm of road safety policies, global factors impact national territories.
Research question Figure 1 shows a steady decline in Chilean traffic fatality and severe injury rates ( per 10 000 vehicles) between 2000 and 2012. Specifically, traffic fatalities have dropped by roughly 52% ((7.97–3.83)/7.97) and severe injuries by 56% ((38.01– 16.53)/38.01). This figure also shows a less pronounced decline in traffic fatality ( per 100 000 population) and severe injury rates ( per 10 000 population). Particularly, traffic fatalities under this indicator dropped by approximately 21% ((11.02– 8.75)/11.02) and severe injuries by 28% ((5.25–3.77)/5.25). Table 1 documents cross-regional variation in traffic fatality and serious injury rates in 2000 and 2012, the two end-year sample points for both rates: vehicle fleet and population. These numbers suggest significant cross-regional variation in fatality and severe injury rates in the year 2000. In 2000, five regions, O’Higgins, Maule, Biobío, La Araucanía and Los Lagos, had an average of 12.1 traffic fatality rates per 10 000 vehicles, while, with the clear exception of the Magallanes region, all the other regions had an average of 6.81. A very similar pattern is observed in fatalities per 100 000 population. We observe the Magallanes region to be the exception with the lowest rate of 4.56. On the other hand, O’Higgins, Maule, Biobío, La Araucanía, Los Lagos and Atacama had an average of 14.4, and all the other regions an average of 9.49. Regarding severe injury rates for the same year, we observe that Atacama, Coquimbo, Biobío, La Araucanía, Los Lagos and Aysén had an average of 46.18 per 10 000 vehicles, whereas the group composed of Tarapacá, Antofagasta, Valparaíso, O’Higgins, Maule and the Metropolitan region had an average of 34.80. For this particular rate as well Magallanes has a very low rate of 24.40. When we analyse the severity rate per population, Atacama is the region with the highest rate with an average of 79.17, Los Lagos region had the lowest rate with 44.27 and all the other regions had an average of 53.4. The first four columns for the year 2012 indicate that variation between and within regions has decreased overall. Thus, the regional data point to overall decreases in traffic fatality and severe injury in both vehicles and population rates, 160
Table 1 Variation in fatalities, serious injuries and crashes, 2000–2012
Regions 2000 Tarapacá* Antofagasta Atacama Coquimbo Valparaíso O’Higgins Maule Biobío La Araucanía Los Lagos† Aysén Magallanes Metropolitana 2012 Tarapacá* Antofagasta Atacama Coquimbo Valparaíso O’Higgins Maule Biobío La Araucanía Los Lagos† Aysén Magallanes Metropolitana
Fatalities per 10 000 vehicles
Fatalities per 100 000 population
Severe injuries per 10 000 vehicles
4.99 7.73 8.85 7.35 6.92 11.52 11.06 13.82 14.13 12.07 6.42 1.90 5.46
9.35 12.25 13.45 8.45 10.37 16.96 14.81 15.10 15.00 12.54 8.53 4.56 8.01
29.82 35.80 52.10 43.98 36.99 32.85 37.63 46.09 49.83 42.61 42.52 24.44 35.68
55.89 56.74 79.17 50.56 55.43 48.37 50.38 50.36 52.91 44.27 56.53 58.71 52.37
5.60 5.70 4.40 4.65 3.13 5.56 4.88 5.84 5.88 5.47 2.74 2.77 2.29
16.46 14.96 12.64 10.14 6.88 13.55 12.90 11.76 9.83 10.09 8.4 9.3 5.3
17.79 15.62 18.96 16.91 18.90 15.96 14.49 29.14 25.77 21.03 9.43 15.88 11.91
49.77 40.97 54.46 36.93 41.55 38.88 38.30 58.71 43.08 37.13 29.03 53.86 27.58
Severe injuries per 100 000 population
*Includes Arica and Parinacota territories. †Includes Los Rios territory.
and a convergence across regions. One potential explanation for these parallel trends could lie in the enactment of a comprehensive traffic law reform in 2006, which may have impacted police traffic enforcement. However, as we can observe in figure 1, a decreasing tendency was evident before the enactment of this law, particularly for fatalities per 10 000 vehicles and severe injuries per 1000 vehicles. There are other elements that, as noted in the literature, should be considered since traffic laws changes might be confounded with other significant factors or not strong enough to influence variation in these rates. For instance, several studies have indicated that increasing oil prices,32 33 alcohol prices,34 35 infrastructure development6 36 or unemployment37 38 can also help produce a downwards tendency. Furthermore, a more direct pathway might also be found in changes in police enforcement practices, particularly in the Chilean context where the centralised nature of this state ensures that these practices are uniformly applied across regions.
METHODS Data Outcome variables Data on (i) traffic fatalities and (ii) severe injuries were obtained from Chile’s National Commission of Road Safety of the Ministry of Transport. This organisation has compiled, from Nazif-Munoz JI, et al. Inj Prev 2015;21:159–165. doi:10.1136/injuryprev-2014-041358
Original article
Figure 1 Traffic fatalities per 10 000 vehicles and 100 000 population and severe injuries per 1000 vehicles and 10 000 population, 2000–2012. police reports, an extensive dataset of traffic fatalities and injuries in Chile from 1972 to the present. Complete data for all 13 regions are available from 2000 to 2012. This provides us with a balanced sample with N=169 region-year observations. Fatalities are classified according to status (driver, passenger, motorcyclist, bicyclist and pedestrian), age, sex and time and day of accident. Following the Chilean Penal Code, police officers classify injuries as severe (ie, injury which prevents the person from performing acts, which constitute such person’s usual and customary daily activities, at least 30 days or more immediately following the occurrence of the injury), less severe (injury which prevents the individual from returning to previous activities up until 30 days immediately following the occurrence of the injury) and minor (injury which does not require immediate medical attention). Data on vehicle fleet and population were both obtained from the National Institute of Statistics. Traffic fatalities and serious injuries per 10 000 vehicles and per 100 000 population were the outcome variables assessed in this study, for a total of four dependent variables. By analysing these variables separately, we may be able to identify the specific impact of each policy in similar, but not identical, outcomes. Last, by introducing the two denominators (vehicle fleet and population), we facilitate international comparisons of the results as well as test robustness across models.
Independent variables ‘Traffic law reform’ was coded as a yearly dummy variable, ‘0’ being the 2000–2005 period when the law had not been approved, and ‘1’ being the 2006–2012 period when the reform was in force. ‘Police per 100 000 population’ is the national number of police officers, using data from United Nations Office on Drugs and Crime. ‘Police traffic enforcement’ is measured as the number of traffic tickets processed by local courts, using data provided by the Ministry of Justice, divided by the national number of police officers, using data from United Nations Office on Drugs and Crime. It must be noted that due to security reasons, the Chilean Police Force (Carabineros de Chile) only provides information regarding the number of police officers at the national level. Thus, the operationalisation of ‘Police traffic Nazif-Munoz JI, et al. Inj Prev 2015;21:159–165. doi:10.1136/injuryprev-2014-041358
enforcement’ is number of tickets per region and year divided by the national number of police officers per year. While the literature suggests number of police officers9 39 or number of traffic tickets40 as separate proxies of police traffic enforcement, we actually propose a combination of these two factors to capture more accurately this road safety measure. First, since police officers have duties other than patrolling traffic, we recognise that an increase in the number of police officers cannot be assumed to automatically lead to a commensurate increase in traffic ticketing. Second, because significant changes in the total number of police officers can actually trigger any absolute increase in the number
Table 2
Summary statistics, 2000–2012 Observations
Dependent variables Traffic fatalities per vehicle Traffic severe injuries per vehicle Traffic fatalities per population Traffic severe injuries per population Independent variables Traffic law reform Police officers per 100 000 population Police traffic enforcement Controls Road infrastructure investment Oil price average Alcohol consumption Percentage of young male population Unemployment
Mean
SD
Min
Max
169
4.182
0.430
2.944
4.950
169
5.821
1.010
3.433
8.085
169
2.423
0.314
1.518
3.125
169
3.843
0.203
3.166
4.371
169
0.538
0.5
0
1
169
5.496
1.183
2.903
8.529
169
17.035
1.092
12.651
19.372
169 169 169
6.244 4.203 11.646
0.261 0.116 1.084
5.694 3.814 9.029
6.667 4.365 14.007
169
−2.559
0.342
−3.756
−1.897
161
162
(0.027) (1.305) (0.228)** (0.097)** (0.104) 0.000 0.871 0.465 0.193 0.032 Yes Yes 0.56 (0.031) (1.177) (0.237) (0.217) (0.070) 0.000 0.871 0.465 0.193 0.032 Yes Yes 0.46 169 (0.027) (1.205) (0.243) (0.076)*** (0.101) (0.031) (1.176) (0.237) (0.217) (0.070)
**p
