Collisions and traffic violations of alcohol, cannabis and cocaine abuse clients before and after treatment.

Prior research has shown that those with alcohol problems have significantly elevated rates of traffic events (i.e. traffic violations and collisions) than licensed drivers from the general population and that treatment is associated with reductions in alcohol-related collisions. However, very little research exists on traffic events and the impact of treatment for cannabis or cocaine clients. The objectives of this research are: (1) to determine whether clients in treatment for a primary problem of alcohol, cannabis or cocaine have significantly elevated rates of traffic events than a matched control group of licensed drivers; and (2) to assess whether a significant reduction in traffic events occurs after treatment for each client group compared to a control group. Driver records of patients admitted to substance abuse treatment in 1994 for a primary problem of alcohol (n = 117), cannabis (n = 80) or cocaine (n = 169) were accessed from the Ministry of Transportation for Ontario, Canada. A comparison group of 504 licensed drivers frequency matched by age, sex and place of residence, was also randomly selected. Data was collapsed into two 6-year time periods: 1988-1993 (i.e. before treatment) and 1995-2000 (i.e. after treatment). Six repeated measures analysis of variance tests were conducted where traffic violations and collisions of three treatment groups (i.e. alcohol, cannabis or cocaine) and a control group were compared before and after treatment. All three treatment groups had significantly more traffic violations than the control group and no significant interactions between time period and group membership were found. For collisions, there was a significant interaction between the alcohol and control groups and between the cocaine and control groups. The average number of collisions for the alcohol and cocaine groups decreased after completing treatment, whereas the number for the control group was stable over the same time periods. Neither the interaction term nor the between group effect was significant in the comparison of the cannabis and control groups. When rates of collisions were calculated based on the period that each driver had a valid license, the interaction term was still significant for the comparison of the alcohol and control groups but not for the cocaine and control groups. The results contribute to existing literature by demonstrating that cocaine and cannabis clients have a higher risk of traffic violations than matched controls and that reductions in collision risk was found after treatment for the alcohol and cocaine groups. More research is needed to better understand the reasons for the higher risk of traffic events and to determine reasons for declines. Copyright 2003 Elsevier Ltd.