This report generally concerns "per se laws" statutes that define impaired-driving offences in terms of the concentration of alcohol in drivers' breath, blood, or other body fluid. In essence, per se laws make valid results of chemical tests, performed as specified by other laws or regulations, irrefutable evidence of the offence. Thus, to convict drivers of en offence defined solely in terms of BAC requires neither evidence of physical or mental impairment nor evidence of impaired-driving behaviour. Nonetheless, almost all per se laws define offences that are implicitly alcohol-impaired driving offences -- and these laws are both rationalized and justified on that basis. In the study reported here, we were especially interested in questions raised by laws that make (or by proposed laws that would make) driving with relatively low concentrations of alcohol en offence per se: 1) Is there a minimum BAC below which the performance of all drivers may be presumed unaffected by alcohol?; 2) In what ranges of BAC is the ability to drive diminished for some, most, end all persons?; 3) Is there a minimum BAC below which the risk of crash involvement does not differ from that of the nondrinking driver?; 4) In what ranges of BAC is the risk of crash involvement increased for some, most, and all drivers?; 5) Do BAC limits in laws end regulations influence behaviours related to drinking end driving? If so, how?; and 6) Does legislation lowering BAC limits decrease the frequency of alcohol-impaired driving and its consequences? Our work had as its starting point two studies done by TIRF and sponsored by the Department of Justice, Canada. The first study concerned possible revisions of impaired-driving statutes in the Criminal Code of Canada (Donelson and Beirness 1985). The second study dealt with youth, alcohol, end road accidents; in particular, we examined why young drivers appear to have an increased risk of crash involvement in lower BAC ranges relative to the average nondrinking driver (Donelson et al. 1987). Because of their relevance to the study reported here, we briefly review the findings of our previous work. (a)
Samenvatting