Cost benefit analysis of the Irish alcohol interlock program

Goldenbeld, Ch.; Houwing, S.; Wijnen, W,; Decae, R.; Eenink, R.

Drink-driving is a major factor in road crashes, fatalities and injuries. Legislation, enforcement, education etc. have proven to be effective in bringing drink-driving levels down. However, still too many drivers repeatedly drink and drive and pose a substantial threat to road safety. This group is not sensitive to ‘traditional’ drink-driving measures. Several countries have, therefore, implemented an alcohol interlock program (AIP). The alcohol interlock is a breathalyser device that prevents the vehicle from starting if the driver is not sober. When the driver blows into the device, an alcohol-specific sensor analyses the breath sample and calculates the blood alcohol concentration (BAC). The engine can be started only if the BAC is below the designated limit.
An Alcohol Interlock Program offers offenders who would normally lose their licence the opportunity to continue driving, as long as they are sober. Preventing these offenders from driving under the influence of alcohol will have a positive effect on the number of road crashes, fatalities and injuries.

The Irish Government Road Safety Strategy 2013-2020 (RSS) sets out 144 actions for the Road Safety Authority (RSA) and stakeholders to have completed by 2020. Action 121 requires RSA to “Undertake a cost benefit analysis for the use of alcohol interlocks as a sanction for repeat offenders.” RSA has commissioned SWOV, the Dutch road safety research institute, to do this.

In Ireland, a large number of people are convicted for drinking and driving. The share of repeat offenders from 2013 to 2016 was 13% on average. For the purpose of this study, this percentage was used in the cost benefit analysis.

The main goal of this study is to determine the two elements of the desired cost benefit analysis: the benefit to cost ratio (BCR) and net present value (NPV) of an Irish Alcohol Interlock Program (AIP). To meet this goal, six research questions on the AIP need to be answered, regarding the number of casualties to be reduced, characteristics of the program, effectiveness, methodology and data, BCR and NPV for different scenarios, and sensitivity to the most relevant input parameters.

The CBA covers a 10-year timeframe (2021-2030) with three different casualty development trends being considered. The most likely trend is based on a model. A more positive trend is the supposed result adhering to EU policy, assuming numbers will be halved in a decade. A more negative trend assumes road fatalities stay at the 2018 level.

The AIP is assumed to be a two-year mandatory program for the participant who bears the cost of the program, as is general practice internationally (e.g. Netherlands, Sweden, Finland and France). In addition, the CBA also includes an alternative AIP scenario where costs are fully borne by the state of Ireland. This is done because it will have a positive effect on participation rate and subsequently the benefits of the program.

In all scenarios, the BCRs and NPVs are favourable. The most likely implementation of the AIP, will result in a BCR of 6.1 and an NPV of 52 million euros. This implies an Irish AIP is likely to be efficient and effective. The output of a model is sensitive to variations in the used input parameters and these have been detailed in the report.

Gepubliceerd door
SWOV, The Hague


Dit is een publicatie van SWOV, of waar SWOV een bijdrage aan heeft geleverd.