This national study has a number of important findings. First, it reports that substantial proportions of young people in their early adolescent years report recent driving of a car or other off-road motor vehicle after consuming alcohol, marijuana or other illicit drugs, or riding as a passenger in a car or off-road motor vehicle with a driver who has consumed alcohol, marijuana or other illicit drugs. Second, it demonstrates that clear inequities exist in the engagement in these health risk behaviours, with the highest proportions reported by youth from rural communities, males, older age groups, and socio-economically disadvantaged populations. Finally, it shows that these behaviours are not innocuous in terms of their potential health consequences. Reports of potential impaired driving were consistently associated with increased risks for motor vehicle injuries at the level of the individual student and at the population level.
Substantial portions of young adolescent Canadians are exposed to potential impaired driving behaviours. Given the magnitude of the traumatic motor vehicle-related injury problem in North America, 
and the fact that approximately one-third of fatal crashes can be attributed to impaired driving, especially in populations of youth, 
this is quite significant. Despite being established as a major risk factor for traumatic injury, and being the focus of a myriad of educational and regulatory interventions, 
such behaviours clearly persist. Our study varied from most efforts used to quantify such behaviours because of our specific focus on young adolescents, and our use of an inclusive definition of vehicle use that considered both on-road vehicles such as cars, and off-road vehicles such as snowmobiles, all-terrain vehicles, and dirt bikes. We studied populations of young adolescents who, with few exceptions, had not reached the age required to obtain a driver's license in their province or territory. Our focus on driving contexts that extend beyond typical on-road situations is also novel to the public health literature. Taken together, our findings suggest that impaired driving is a public health problem that extends to populations of children in their early teenage years. This problem also extends beyond the typical on-road drinking and driving scenarios, to ones that include use of alcohol and other drugs on a variety of off-road vehicle types.
A major purpose of our study was to investigate inequities in exposure to potential impaired driving behaviours among young people in Canada and related injury. Through this analysis, we provided basic evidence about variations in high-risk behaviours. Increases in exposure to potential impaired driving among boys and students in the older age groups were expected given well known gender differentials in risk-taking and substance use, 
as well as the increase in motor vehicle use anticipated with reaching the age of possible drivers license acquisition in Canada. The consistency of observed increases in risk reported by young people from rural communities was of greater interest as a potentially modifiable health inequity. Such youth populations are known to suffer considerable disadvantages when it comes to their health, whether measured in terms of standard indicators of mortality and morbidity, as well as their underlying causes. 
Our analysis extends this finding for rural settings to injury-related health behaviours.
Several explanations exist for the higher reported exposures to potential impaired driving behaviours among young people from rural communities. Because most members of our study population were not old enough to hold a driver's license, a portion of these increases are attributable to youth riding as a passenger in a motor vehicle or while using off-road vehicles. All-terrain vehicles, snowmobiles and dirt bikes can be operated legally by minors on private property, and their use is more common in rural settings. Second, differences in the built environment and the policies that govern it may exist between rural and urban areas. In urban areas, there are typically formal options for travel for young people including public transit and taxis. Such options do not exist to the same extent in more rural communities, leading to greater reliance on private transportation and informal arrangements for travel, with accompanying risks for impaired driving. Differences in cultural norms surrounding overt risk-taking may also exist with a coincident greater tolerance for such risk behaviours in some cultures. Drinking and driving behaviours exhibited by parents are highly correlated with increased risks for such behaviours in new drivers. 
Speculatively, this phenomenon might contribute to higher reported exposures to potential impaired driving behaviours in rural areas should such communities be home to a drinking and driving culture that crosses generations.
Our analysis provides evidence for the existence of additional health inequities. To illustrate, high levels of engagement in potential impaired driving behaviours were reported by young people from socio-economically disadvantaged populations in all urban-rural community settings. These social variations are obviously complex and multi-factorial in terms of their origins. Population health theory, and most recently the report on the WHO Commission on the Social Determinants of Health, 
suggests that determinants of health involve both individual factors as well as characteristics of the social and physical settings in which these factors are manifested. It is clear that at least part of the observed inequities in injury-related risks are attributable to differences in overt risk behaviours, but that these behaviors are likely affected, if not caused by, varying social norms within youth cultures as well as aspects of their social and built environments. We feel our findings confirm those of others 
indicating that health is determined in part by individual behaviour, but that features of social and physical environments may be at the root of observed unfair differences in health risks and adverse health outcomes. These differences require further and deeper exploration.
Strengths and limitations of this study warrant comment. Major strengths include the novelty of this analysis with respect to its focus onpotential impaired driving in young adolescents, its national scope, and its focus on injury-related health experiences of an important yet understudied group. Foundational evidence gained from our analyses provides a first step for the planning of effective countermeasures for adolescent populations. Our confirmation of inequities between several vulnerable population subgroups too points to the complex etiology of injury-related health disparities. This is of importance to public health at the population level.
The study also has several limitations. The HBSC survey is necessarily reliant on the provision of accurate information from children obtained via self-report. While considerable efforts are made to use established questionnaire items that have been subject to checks for reliability, 
some misclassification is inevitable. Second, participation in the HBSC was voluntary and the response rate was 59% at the school level and 77% at the individual student level, with variation in response rates according to whether implicit or explicit consent was used. It is possible that non-respondents had differential experiences with the impaired driving and associated injury measures. For example, requirements for explicit consent very likely decreased response among groups of young people who were most vulnerable to the potential impaired driving behaviours leading to underestimates of prevalence and risk. Such patterns of non-response are unlikely to affect relations between the impaired driving behaviours and injury save for a loss of statistical power expected due to lower numbers of exposed students being available for analysis.
Our use of composite measures for potential impaired driving behaviour represents a third limitation. It was not possible to establish the exact driving contexts in which these potential impaired driving behaviours occurred. We were unable to distinguish, for example, the use of alcohol from other drugs prior to driving or riding and subsequently quantify any differences in the effects of specific types of substance use on risks for injury. For example, when alcohol and cannabis are taken together, some argue that it is the alcohol that is consumed that is solely responsible for any risk increase 
while others conclude that use of either substance, alone or in combination, contributes to such risks 
. We were unable to develop analyses to assist in resolving these debates. Fourth, because of our use of a composite measure for motor vehicle use, we were unable to distinguish the exact types of vehicles being operated and the contexts in which potential impaired driving behaviour occurred. As study participants were below the legal age for driver's license acquisition in most provinces and territories, almost all reported vehicle operation likely took place in off-road situations. Knowledge of the context of these specific risk-taking behaviours would assist in prevention efforts. In future cycles of the Canadian HBSC, the questionnaire items will be modified to provide this level of specificity. Finally, these are cross-sectional analyses and therefore caution is warranted in the causal interpretation of the observed relationships in the absence of longitudinal confirmation.
Our findings have implications for adolescent health policy. Ongoing surveillance of potential impaired driving behaviours in populations of young people, including those below the typical ages for driver's license acquisition, is of inherent value to policy development. Not only do our surveillance efforts quantify the magnitude of these problem behaviours and establish the need for public health interventions, they also point to vulnerable groups within the Canadian population and the possible combination of factors affecting their risk for, and experience of, impaired driving related injury. Surveillance findings also help to target prevention efforts. Surveillance also provides one potential basis for measuring the impacts of ongoing public health programs. Our findings of higher reported levels of exposure to potential impaired driving in rural communities and socio-economically disadvantaged groups call for innovative solutions specific to local contexts. Prevention strategies that are known to be effective include innovations in public and private transportation options for young people where possible, increased enforcement of impaired driving laws for both on-road and off-road vehicles, establishment of behavioural contracts between parents and teens, as well as targeted public education initiatives. 
Finally, there is a need for more policy-oriented research, both etiological and intervention, that is centered upon the root causes of impaired driving in Canada and its inequities. The latter may include furthering understanding of the etiology of problem drinking and substance use behaviours in young people, the social conditions that determine such behaviours, and sensible points of intervention within specific community settings.
In summary, this Canadian analysis examined potential impaired driving behaviours among populations of young adolescents using contemporary health survey data. Such behaviours were common in the overall study population, and also were related to the occurrence of higher risks for motor vehicle-related injury. Reported inequities in the involvement of young people in these risk behaviours were identified, and suggest the need for targeted interventions within rural communities, and among socially disadvantaged populations of Canadian youth. These behaviours and inequitable high-risk groups clearly remain as priorities for public health efforts within adolescent populations in our country.