The alcohol ignition interlock and other technologies for the prediction and control of impaired drivers

Abstract

This chapter summarizes the context and evidence supporting the use of alcohol ignition interlocks (also known as alcolocks) as an approach to improving road safety. Interlocks usually have four features: (1) an in-vehicle sensor that requires a breath sample and prevents engine starts if alcohol level exceeds some criterion such as blood alcohol concentration (BAC) ≥ 0.02 g/dL; (2) a running retest feature which requires at least one retest after the car has been started, often every 15 to 45 minutes while driving; (3) a tamper-detecting installation in the engine compartment; and (4) a data-recording feature that logs the time and level of all BAC tests, starts, stops, and procedural violations. These devices form the base of an interlock program that, depending on the quality of the policies, reporting procedures, and user supports, can range from very weak to very effective. The USA through the National Highway Traffic Safety Administration, (NHTSA), Canada through Transport Canada, Australia through Standards Australia, and the European Commission through CENELEC have promulgated standards and guidelines in an effort to make these devices and their programs maximally effective. This report provides some background and context for the development of interlock programs and then focuses on the evidence for interlock program effectiveness and promising aspects that are still under-exploited. Reports that have combined data from multiple studies estimate that interlocks account for 65 % reductions in driving while impaired DWI recidivism, a beneficial effect that is usually limited to the period of installation. Currently, there are still too few interlocks in service to substantially alter the rate of alcohol-impaired crashes. The attainment of ideal program features is a work in progress, and all developed nations that have taken an interest in interlocks are actively groping toward a set of best practices. © 2009 Birkhéuser Verlag/Switzerland.