Section 5


  • Acute impairment is an immediate contraindication to driving.
  • Patients suspected of having an alcohol use disorder should be assessed to determine the nature of the problem and should be advised not to drive until the condition has been effectively treated and remission has been achieved.
  • Abstinence-based recovery is the treatment of choice for alcohol dependence to prevent recurrent impaired driving.

5.1 Overview

Alcohol is a depressant drug that has both sedative and disinhibitory effects. It also impairs a driver’s judgment, reflex control, and behaviour toward others. Impairment from alcohol use is the single most common risk factor for motor-vehicle–related crashes and injury. The overall availability of alcohol has been identified as a factor associated with the incidence of impaired driving (American Psychiatric Association, 2013). Recent changes in public policy in various jurisdictions that have loosened restrictions for public use of alcohol provide greater opportunities, especially for underage users, and increase the probability of alcohol-impaired driving (Canadian Centre on Substance Use and Addiction, 2020).

People charged by police for impaired driving will have their driving privileges restricted according to provincial or territorial legislation. The guidelines provided here are not meant to conflict with such legislation.

In some people who are regular users of alcohol, withdrawal from alcohol may trigger seizures. For information about seizures induced by alcohol withdrawal, see Section 11.4.7.

5.2 Assessment: Clinical history

Researchers have identified a group of drivers (often referred to as “hard-core drinking drivers”) who drive with blood alcohol levels averaging twice the legal limit, have previous driving convictions and licence suspensions, may drive without a valid driving licence, and likely need treatment for an alcohol use disorder.

Most of the studies included in a recent systematic review found that alcohol use disorder is associated with increased risk of a motor-vehicle–related crash, and one study showed that the risk increased with the severity (grade) of the disorder (Charlton et al., 2021).

A number of clinical “red flags” have been identified, which may indicate ongoing alcohol use that will impair ability to drive safely (American Psychiatric Association, 2013). These indicators include the following:

  • driver with at least one previous driving offence, especially an alcohol- or drug-related offence
  • driver arrested with blood alcohol concentration of 32.6 mmol/L (equivalent to 0.15% or 150 mg/100 mL) or more (the low risk of detection implies that they have probably driven in this condition previously)
  • clinical diagnosis of alcohol dependence or abuse (“alcohol use disorder” in the Diagnostic and Statistical Manual of Mental Disorders [DSM-5; American Psychiatric Association, 2013])
  • resistance to changing drinking-and-driving behaviour, often associated with antisocial tendencies such as aggression and hostility
  • concomitant use of illicit drugs (e.g., alcohol and marijuana or alcohol and cocaine in combination; when ingested concomitantly, the latter combination leads to the formation of cocaethylene, a dangerous, longer- lasting toxic metabolite)
  • male gender
  • age 25–45 years
  • education level: high school or less
  • history of prior traffic or other criminal offences
  • risk-taking behaviour in situations other than driving
  • evidence of poor judgment in situations other than driving
  • evidence of aggression in situations other than driving
  • lifestyle associated with fatigue and lack of sleep
  • intoxication at the time of a routine office visit.

People demonstrating drinking-and-driving behaviour, those showing evidence of driving while impaired, and those assessed as having a high probability of driving while impaired should not drive any motor vehicle until they have been further assessed.

Physicians need to be familiar with the signs and symptoms that would raise concerns about drinking and driving. Screening and assessment for appropriate referrals need to be considered, in addition to reporting patients to the provincial ministry of transport, in accordance with applicable provincial legislation. Physicians should be aware that, in some jurisdictions, reporting drinking-and-driving behaviour to licensing authorities might lead to immediate suspension of the person’s licence pending further assessment.

A driver who has had their licence suspended because of a diagnosis of alcohol use disorder may request reinstatement under certain circumstances, such as sustained remission. It is therefore important for primary care physicians to monitor patient adherence to treatment recommendations and recovery, as they may be required to submit progress reports or to confirm the patient’s sustained remission.

The risk of relapse remains for the duration of the person’s life. Clinical judgment is required in assessing the risk of drinking and driving. Consultation with an addiction medicine physician should be considered in cases where the primary care physician has any degree of uncertainty about the individual’s adherence to abstinence-based recovery.


American Psychiatric Association. Diagnostic and statistical manual of mental disorders . 5th ed. Washington (DC): American Psychiatric Association Publishing; 2013.

Canadian Centre on Substance Use and Addiction. Research: Driving under the influence of alcohol. Toronto (ON): The Centre; 2020. Available: (accessed 2022 Aug. 5).

Perazzolo M, Odell M, Ryan M, Sheehan JD, Flannery W, Gilvarry E, et al. Influence of alcohol use disorders on MVC risk. In: Charlton JL, De Stefano M, Dow J, Rapoport MJ, O’Neill D, Odell M, et al., project leads. Influence of chronic illness on crash involvement of motor vehicle drivers. 3rd ed. Report 353. Victoria, Australia: Monash University Accident Research Centre; 2021 Mar. p. 11-20. Available: data/assets/pdf_file/0008/2955617/Chronic-illness-and-MVC-risk_Report-MUARC-report-no-353_JUNE2022.pdf (accessed 2022 July 4).

Other resources

American Geriatrics Society; Pomidor A, editor. Chapter 9: Medical conditions, functional deficits, and medications that may affect driving safety. In: Clinician's guide to assessing and counseling older drivers. 3rd ed. Report No. DOT HS 812 228. Washington (DC): National Highway Traffic Safety Administration; 2016 Jan. p. 126-89. Available:… (accessed 2022 July 28).

American Society of Addiction Medicine. The ASAM criteria: treatment criteria for addictive, substance-related, and co-occurring conditions. 3rd ed. Chevy Chase (MD): The Society; 2013.

American Society of Addiction Medicine, Practice Improvement and Performance Measurement Action Group and Standards and Outcomes of Care Expert Panel. The ASAM standards of care for the addiction specialist physician. Chevy Chase (MD): The Society; 2014. Available: (accessed 2022 July 28).

American Society of Addiction Medicine. Definition of addiction. Rockville (MD): The Society; 2019. Available: (accessed 2022 July 28).

Babor TF, Higgins-Biddle JC, Sanders JB, Monteiro MG. AUDIT: the alcohol use disorders identification test. Guidelines for use in primary care. Geneva: World Health Organization; 2001. WHO/MSD/MSB/01.6a. Available: (accessed 2022 July 29).

Canadian Council of Motor Transport Administrators. National Safety Code. Standard 6. Determining driver fitness in Canada. Part 1: A model for the administration of driver fitness programs. Part 2: CCMTA medical standards for drivers. Ottawa (ON): The Council; 2021. Available:… (accessed 2022 July 4).

Ewing JA. Detecting alcoholism: the CAGE questionnaire. JAMA. 1984;252(14):1905-7.

Koob GF, Le Moal M. Chapter 5: Alcohol. In: Neurobiology of addiction. London (UK): Elsevier/Academic Press; 2000. p. 173-241.

Marques PR, Tippetts AS, Yegles M. Ethylglucuronide in hair is a top predictor of impaired driving recidivism, alcohol dependence, and a key marker of the highest BAC interlock tests. Traffic Inj Prev. 2014;15(4):361-9.

Miller SC, Fiellin DA, Rosenthal RN, Saitz R, editors. The ASAM principles of addiction medicine . 6th ed. Philadelphia (PA): Lippincott, Williams &Wilkins; 2018.

Shuggi R, Mann RE, Zalcman RF, Chipperfield B, Nochajski T. Predictive validity of the RIASI: alcohol and drug use and problems six months following remedial program participation. Am J Drug Alcohol Abuse  2006;32(1):121-33.