Evaluation of an increase in roadside drug testing in Victoria based on models of the crash effects of random and targeted roadside tests

Drug driving continues to be overrepresented in both fatal and serious injury crashes in Victoria. As an enforcement countermeasure, preliminary oral fluid tests to detect drug driving were introduced in Victoria, Australia in December 2004. Recent research has modelled the relationships between prevalences of THC and methamphetamine in fatally and seriously injured drivers and (a) the annual numbers of random and targeted drug tests during 2010-2016 and (b) the positive detection rates from these tests. The increase in roadside drug tests in Victoria from 42,000 in 2013 (1% of licensed drivers) to 100,000 per year (2.2% of drivers), particularly targeted tests, is estimated to have saved 33 fatal crashes (13.7% reduction) and at least 80 serious injury crashes (1.4% reduction) per year. Based on the findings from this research, further increases in targeted and random roadside drug tests are warranted, up to at least 390,100 total tests per year, which are estimated to save a further 46 fatal crashes and at least a further 134 serious injury crashes per year.