Introduction

Alcohol interlocks have been recognised as an effective and important component of the strategy to deal with impaired drivers.1 ,2 An interlock is a small breath-testing device connected to the engine to prevent a vehicle from being driven if the driver's blood-alcohol concentration (BAC) is above a low preset level (usually 0.02%). Interlocks contain sophisticated anticircumvention features and computerised data logs that record the results of all breath tests and attempts to tamper with the device. Over the past few decades, various jurisdictions have introduced interlock programmes as an impaired driving countermeasure. Accordingly, interlocks have been the subject of extensive consultation and collaboration among researchers and policy-makers worldwide.3 This has resulted in a catalogue of ‘best practices’ that is generally supported by researchers and readily accessible to governments and licensing authorities.4 Nevertheless, there remains a relatively disparate set of interlock programmes in force around the world. The variety of programmes is particularly obvious in federal nations, like Canada, where each province and territoryi has authority over driver and motor vehicle licensing.