Mobility and transport

Alcohol interlocks

The opinions expressed in the studies are those of the consultant and do not necessarily represent the position of the Commission.


Alcohol interlocks

(See also Alcohol webtext)

What are alcohol interlocks?

Alcohol interlocks are automatic control systems which are designed to prevent driving with excess alcohol by requiring the driver to blow into an in-car breathalyser before starting the ignition. The alcohol interlock can be set at different levels and limits.

What road safety problem do alcohol interlocks address?

Excess alcohol contributes to about 25% of all road deaths in Europe. A large part of the problem consists of 'high risk offenders' who offend regularly and/or exceed legal blood alcohol levels by a large amount. With a BAC of 1.5 g/l the crash rate for fatal crashes is about 200 times that of sober drivers. In some countries e.g. Britain, levels of police enforcement of legal limits has dropped in recent years, leading to increases in drinking and driving. Alcohol interlocks address excess alcohol in the driving population at large, as well as repeat offenders.

How effective?

Large scale quantitative research on alcohol ignition interlocks in use has shown that alcohol interlocks are 40 to 95 percent more effective in preventing drink driving recidivism than traditional measures such as license withdrawal or fines [45]. A literature review (UK Department for Transport, 2004) showed a recidivism reduction of about 28-65% in the period where the alcohol interlock is installed compared with the control groups who were not using the alcohol interlock. An EU study indicated that alcohol interlocks need to be fitted permanently to have an effect, for after removal of the lock recidivism increases again [5]. Alcohol interlocks clearly have an important role to play within rehabilitation programmes.

There has been no evaluation of the impact that alcohol interlocks used in commercial transport have on road safety but Swedish companies report that fitting alcohol interlocks prevented excess alcohol amongst fleet drivers.

Benefits to cost?

In a recent cost benefit analysis, estimations are made for implementing alcohol interlocks for drivers caught twice with a BAC between 0.5g/l and 1.3g/l and for drivers caught with a BAC above 1.3g/l in several countries [55].

Benefits to cost of alcohol interlocks in different countries [55]

  • For the Netherlands, the reduction of 35 traffic fatalities annually is valued at 4.8 million per death, leading to a benefit of 168 million Euros.Benefit/cost ratio =4.1
  • For the Czech Republic, the 8 fatalities prevented are counted at 1.1 million Euro/death, leading to estimated benefits of 9 million Euro/year. Benefit/cost ratio = 1.6
  • For Norway, the benefits are calculated as 5.5 deaths less per year a rate of 5.9 million Euro per death, or at 32.5 million Euro /year. Benefit/cost ratio =4.5
  • For Spain, the reduction with 86.5 deaths/year at 800.000 Euro per death would imply benefits of 69 million Euro/year. Benefit/cost ratio = 0.7

Who uses alcohol interlocks now?

These have been used widely in North America and Sweden in rehabilitation schemes for repeat offenders driving with a blood alcohol content over the legal limit. They are also used in government and company fleet cars in Sweden. Trials have been taking place in various countries such as the US, Australia, Canada, Belgium and Sweden.

Alcohol interlock policy and practice in Sweden

In a trial running from 1999 to 2002 in Sweden, 300 alcohol interlocks were installed in commercial passenger and goods transport. Subsequently, manufacturers such as Volvo and Toyota offer installation of alcohol interlocks in trucks as a dealership option in Sweden. One transport company in Sweden decided to equip all their 4000 vehicles with alcohol interlock systems before the end of 2006. From 2006 all trucks of 3.5 tons and over, which are contracted by the Swedish Road Administration (SRA) for more than 100 hours per year, have to be fitted with alcohol interlocks (SRA, ITS Strategy, 2006-9).

More than 5000 company cars in Sweden are today equipped with alcohol interlocks and the number is growing rapidly. The Swedish Driving Schools Association has fitted all their 800 vehicles with alcohol interlocks [31]. In 2007 Volvo launched an alcohol interlock for normal use in cars.

In 2004 the SRA required that all the SRA's purchased or leased vehicles must be equipped with alcohol ignition interlocks during 2008 at the latest. By 2010, 50% of all new cars used by companies in Sweden should have alcohol interlocks [46].

Next steps for implementation?

Sweden has recently introduced a strategy on alcohol interlocks and the rehabilitation of offenders and has proposed that from the year 2012, all new cars should have an alcohol ignition interlock installed. However, Sweden is the only EU Member State that uses alcohol locks at present, even in rehabilitation programmes, although experiments are being carried out in Spain, Belgium, Germany, and Norway. More widespread application will require a technical specification to be devised for alcohol interlocks as well as debate about their use, whether for rehabilitation or in normal use.