This article examines this idiosyncratic approach to the criminalisation of drug driving, highlighting its weak correlation with the important road safety objective of deterring substance-impaired driving, and the risks of both over- and under-criminalisation that it creates. It argues that public policy on the prohibition of certain drugs and the criminalisation of their use should be disentangled from public policy on impaired driving. It recommends that drug driving laws in all Australian jurisdictions should be brought back into line with drink driving laws, via legislation and testing practices that turn on substance-specific prescribed concentrations for all drugs (illicit and licit) that have the potential to impair drivers.

That the goals of improving road safety and reducing road accidents and trauma are valid and important is axiomatic. Accordingly, and alongside other measures, the detection of individuals who are driving under the influence of substances that are known to diminish driver capacity is entirely meritorious. The aim of this article is not to question the legitimacy of these objectives, but to scrutinise and produce fresh insights about the way that the criminal law is configured and deployed to this end. Specifically, it investigates whether current drug driving laws and random drug testing (RDT) practices are consistent with the evidence‐based impairment paradigm that has underpinned the success of random breath testing (RBT) and drink driving offences in transforming driving under the influence of alcohol from a common practice to a highly stigmatised criminal behaviour (Terer and Brown 2014). By producing new knowledge about the character of contemporary drug driving laws, we aim to identify reform options that will allow drug driving laws to share the combination of social acceptance, evidence‐based legitimacy and effectiveness that are widely regarded as the hallmarks of drink driving laws  

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