Alcohol and road accident risk—the significance of driver behavioural analysis in scientific research and expert opinion practice

Alcohol affects the basic mechanisms responsible for safe driving. It impairs concentration and the ability to assess road conditions correctly, lengthens reaction time and reduces the ability to anticipate the consequences of one's decisions. Even small amounts of alcohol can reduce a driver's physical and mental performance.

In practice, this means that a driver under the influence of alcohol more often:

• exceeds the speed limit,
• undertakes unjustified overtaking manoeuvres,
• misjudges the distance and speed of other vehicles,
• reacts too late to a hazard,
• makes more impulsive and risky decisions.

From a road safety perspective, alcohol therefore acts not only as a substance that reduces performance, but also as a factor increasing the tendency towards dangerous behaviour.

The scientific studies analysed assessed drivers' behaviour related to alcohol consumption and its association with the risk of involvement in road accidents. The research covered drivers of different ages, with participants divided into groups including people referred for re-education courses after their driving licences were seized for drink-driving and drivers undergoing standard psychological assessment.

To assess alcohol-related problems, the study used the diagnostic questionnaire MPA-13 (Map of Alcohol Problems). This tool analyses not only alcohol consumption itself, but also its relationship with particular behaviours, such as driving after drinking, drinking to reduce stress, interpersonal conflict or impulsive behaviour.

The study analysed, among other things:

• the driver's age and sex,
• level of education,
• annual vehicle mileage,
• attendance at re-education courses,
• frequency of alcohol-related risky behaviours.

This approach helps explain that accident risk arises not solely from alcohol consumption itself, but also from the broader pattern of behaviours and decisions made by the driver.

Research findings show that drivers attending re-education courses more frequently report behaviours indicative of problematic alcohol use. This particularly concerns situations where alcohol becomes part of everyday functioning, a way of reducing tension or a factor influencing impulsive decisions.

Behaviours particularly significant to accident risk include:

• driving after consuming alcohol,
• drinking alcohol to reduce stress or emotional tension,
• aggressive behaviour after drinking,
• work-related problems associated with drinking,
• episodes of excessive alcohol consumption over several consecutive days.

Driving after drinking is, of course, the most significant factor, but research shows that this behaviour is not isolated from other problems. It often forms part of a broader pattern in which reduced behavioural control and greater impulsivity also affect how a person participates in road traffic.

Research into alcohol and driver behaviour is highly relevant to expert reporting in road accident cases. It helps explain which psychological and behavioural mechanisms increase the risk of involvement in an incident and how a driver’s behaviour should be assessed from a road safety perspective.

In expert examination practice, this knowledge may be useful, among other things, for:

• assessing the driver’s behaviour before the incident,
• analysing the risk of returning to drink-driving,
• preparing opinions in criminal and administrative cases,
• assessing the significance of psychological factors in an accident,
• designing preventive and re-education measures.

For an expert opinion, it is important not only to establish that the driver was under the influence of alcohol, but also to understand how this may have affected perception, decision-making, reaction times and the ability to control the vehicle.

In road accident cases, these findings may be relevant to assessing the causes of the incident, whether it could have been avoided and the road user's degree of fault.

Statistical analyses indicate that the likelihood of causing a road accident increases not only with alcohol consumption itself, but also under the influence of other co-occurring factors. The most important include:

• aggression and impulsivity under the influence of alcohol,
• work and social problems associated with drinking,
• high exposure to road traffic, measured, for example, by kilometres travelled,
• established patterns of risky behaviour,
• recurrence of earlier alcohol-related violations.

In practical terms, this means that assessing accident risk should not be limited to blood alcohol concentration alone. Personality traits, the driver’s behavioural history and everyday patterns of functioning also matter.

The research findings clearly confirm that alcohol-related behaviour is a significant risk factor for road accidents. Drivers who have difficulty controlling their alcohol consumption are more frequently involved in road incidents and more frequently make decisions that increase danger on the road.

For court and expert opinion practice, this means a need to combine knowledge of transport psychology, road safety and accident reconstruction. The presence of alcohol in a driver's body does not, by itself, explain the entire mechanism of an incident, but it is an important element of a broader analysis of the road user's behaviour.

Effective prevention therefore requires not only legal sanctions, but also educational, psychological and diagnostic measures. Research into drivers' behaviour after drinking is consequently relevant not only to science, but also to the work of court experts, specialist assessors and justice authorities.