Cost-benefit analysis of an alcohol ignition interlock for installation in all newly registered vehicles

This study conducted a cost-benefit analysis of an alcohol ignition interlock device in preventing alcohol-related fatalities and serious injuries when installed in all newly registered vehicles in Australia.

Benefit-cost ratios (BCRs) were calculated by comparing the benefits associated with the number of road injuries the interlock was predicted to save with the costs associated with installing the device in all newly registered vehicles. Four effectiveness levels were assumed for the interlock, given that the device was not expected to prevent 100 percent of alcohol-impaired driving. Unit benefits were computed for 4, 5, and 7 percent discount rates, and for fleet life periods of 15 and 25 years.

The BCRs ranged from 3.4:1 at best to 0.6:1, depending on the interlock effectiveness level, the discount rate, and the fleet life figure applied. It was estimated that the interlock could prevent between 97 (at the lowest effectiveness level of 23.8%) and 388 (at the highest effectiveness level of 95%) road fatalities per annum, with the corresponding range for serious injuries being 603 to 2414 casualties.

It was recommended that the installation of interlock devices in all newly registered vehicles in Australia could be an effective option, from a cost-benefit analysis perspective, depending upon its level of success in preventing alcohol-impaired driving. Therefore, although this primary prevention strategy is likely to obtain lower BCRs than targeting groups who are overrepresented in alcohol-related road crashes, a substantial number of road fatalities and serious injuries would be prevented, with up to 24 percent of all fatalities and up to 11 percent of all serious injuries saved in Australia per annum. Overall, it was concluded that due to the investigated interlock's user friendliness and relative affordability in comparison to other interlocks, the device should be considered as a countermeasure for curbing the drink driving problem in Australia.