Driving under the influence, a road safety priority

Driving under the influence of alcohol or drugs remains one of the leading causes of road crashes. They impair essential driving abilities such as reaction time, coordination, speed management, attention and vigilance. It is a complex problem influenced by social attitudes, accessibility of substances and individual factors. Despite EU-wide efforts in legislation, enforcement and public awareness, impaired driving continues to pose a serious risk to road safety. Sharing knowledge and good practices remains, therefore, essential. 

This article provides an overview of the key challenges and opportunities in addressing impaired driving. Given the already complex issues around driving under the influence of alcohol and illegal drugs, the impact of medicinal substances has been intentionally excluded from the scope of this discussion.

What do the statistics say? 

Accurately assessing the prevalence of alcohol in road crashes remains challenging. Police roadside checks differ across countries, and controls are often insufficient to provide a reliable picture of how many drivers exceed legal limits (European Transport Safety Council, 2022). Drivers are also more informed about these controls through social media and navigation app alerts, making it easier to avoid them in the event of alcohol consumption. After a crash, alcohol testing is often not systematic and is typically only conducted when police suspect impaired driving. Other road users, such as pedestrians and cyclists, are often not tested. Furthermore, international comparisons are further complicated due to the differences in legal blood alcohol (BAC) limits. An overview can be found here.

Considering these factors and the likelihood of underreporting, the European Commission estimates that about 25% of all road fatalities are alcohol-related (European Commission, 2023). Although this estimation is based on data from 2007-2009, several recent studies have shown similar or even higher results. A Norwegian study found that 25% of their fatally injured were under the influence of alcohol or drugs. At the same time, data from the US and Canada indicate that over half of the injured or killed on the roads had consumed such substances. In both cases, drug use was slightly higher than alcohol use. According to the latest World Health Organisation (WHO) Global Status Report on Road Safety, around 20% of drivers involved in fatal crashes in high-income countries had BAC levels above the legal limit (World Health Organisation, 2023). 

Despite these statistics, there are also some encouraging trends. Between 2011 and 2021, road fatalities involving alcohol consumption dropped by 37% in EU-23 (excluding Bulgaria, Ireland, Italy and Malta), compared with a 30% decline for other road deaths (European Transport Safety Council, 2022). The most significant progress was observed in Romania (-11%), the Netherlands and Cyprus (both -8%). 

Figure 1: Relative developments in recorded road deaths due to alcohol and other road deaths in 23 EU countries over the period 2011-2021. EU23 average excluding BG for inconsistency in the data trend and IE, IT, MT as data on alcohol-related road deaths were not available in these countries for the entire time series. (source: ETSC)

Figure 2: Difference between the average annual (%) changes in the number of road deaths attributed to alcohol and the corresponding change for other road deaths over the period 2011-2021.  (1)2017-2021 (2) 2011 - 2020. EU23 average excluding BG for inconsistency in the data trend and IE, IT, MT as data on alcohol-related road deaths were not available in these countries for the entire time series. ES data from Catalonia and the Basque Country are not included. (source: ETSC)

 

Reliable data on drug use in traffic are even more scarce. The diversity of substances makes roadside drug testing methods costly and time-consuming. The highest crash risks are associated with amphetamines, multiple drug use and the combination of alcohol and drugs. 

The ESRA3 survey, which gathers self-reported data on driver behaviour, provides further insight into alcohol and drug use. Among the participating European countries, 15.4% of drivers reported driving after consuming alcohol in the past 30 days (Meesmann et al., 2024). 16.6% believed they were over the legal limit. 7.2% admitted to driving within one hour of taking drugs, most commonly cannabis. Male drivers reported driving under the influence more often than females, and the overall percentage declined with age. 

Figure 3: Percentage of drivers in the EU who drove within 1 hour after using drugs (Source: ESRA3)

What are the risks? 

Drivers with a blood alcohol concentration of 0.5g/L have a 1.4 times higher crash risk. This risk increases fivefold at 1.0 g/L and twentyfold at 1.5g/L (European Commission, 2023). Alcohol impairs self-awareness, increases self-confidence and encourages risk-taking behaviours such as speeding and unsafe manoeuvres. 

The effects of drugs vary per substance. Amphetamine users are more likely to speed and lose lane control, while cannabis users are often aware of their impairment (Vias, 2022). They often try to compensate for this by driving more slowly, increasing headway or not driving at all. However, the exact impact of different drugs on crash risk is difficult to quantify, as experimental doses for research are typically lower than those found in blood analyses of crash victims. It is estimated that the risk associated with, for example, cocaine use is comparable to a BAC of 0.5-0.8 g/L, and that of amphetamines to a BAC of 0.8-1.2 g/L. 

How can we improve road safety? 

Several factors influence why individuals drive under the influence of alcohol or drugs. These include personality characteristics (such as sensation-seeking, impulsiveness and a sense of invulnerability), the unplanned nature of impaired driving, peer pressure, social circumstances, alcohol affordability and the perceived difficulty of driving (European Transport Safety Culture, 2022). The issue is complex, involving social, medical and psychological aspects. Among repeat offenders, impaired driving often reflects problematic alcohol or drug use. Two-thirds of alcohol-related crashes involve a repeat offender. 

There is, therefore, no single solution to address this road safety problem. Instead, an integrated approach combining multiple measures is required: 

  • Health policies that reduce excessive alcohol consumption (e.g. minimum pricing, higher taxes, stricter marketing rules)
  • Lowering legal BAC limits
  • Visible and consistent enforcement
  • Road safety campaigns to raise awareness and shift social norms
  • Promoting alternative transport options
  • Rehabilitation programmes and alcohol interlocks for repeat offenders
  • Clear company policies, testing and support programmes for professional drivers
  • In-vehicle technologies (drowsiness detection, collision warnings, lane departure systems) 

According to the ESRA3 survey, the most widely supported policy measures are the installation of alcohol interlocks for repeat offenders and zero tolerance for novice drivers (Meesmann et al., 2024). The least supported measure is zero tolerance for all drivers. 

Many members of the European Road Safety Charter work on reducing the number of road crashes related to alcohol and drugs. Some good practices are:

References:

European Commission (2023). Road safety thematic report – Alcohol and drugs. European Road Safety Observatory. Brussels, European Commission, Directorate General for Transport.

European Transport Safety Council (2022). Progress in reducing drink-driving and other alcohol-related road deaths in Europe. Brussels, European Transport Safety Council. 

Meesmann, U., Pires, C., Wardenier, N. (2024). Driving under the influence of alcohol, drugs or medication. ESRA3 Thematic report Nr. 10. ESRA project (E-Survey of Road users’ Attitudes). (2024-R-31-EN). Vias institute. https://www.esranet.eu/storage/minisites/esra2023thematicreportno10drivingundertheinfluenceofalcoholdrugsormedication.pdf 

Vias institute (2022) Briefing “Rijden onder invloed van drugs”. Brussels, Belgium, Vias institute, www.vias.be/briefing

World Health Organization. (2023). Global status report on road safety 2023. Licence: CC BY-NC-SA 3.0 IGO. https://iris.who.int/bitstream/handle/10665/375016/9789240086517-eng.pdf?sequence=1