© 2003, 2010 CAMH
How do alcohol and other drugs affect driving?
When you drive, your hands, eyes and feet control the vehicle, and your brain controls your hands, eyes and feet. To drive
safely, you need to be alert, aware and able to make quick decisions in response to a rapidly changing environment.
Alcohol and other drugs alter the normal function of the brain and body, and interfere with even the most skilled and experienced
driver’s ability to drive safely. While different drugs can have different effects on driving, any drug that slows you down,
speeds you up or changes the way you see things can affect your driving—too often with tragic consequences.
Alcohol and other depressant drugs
Alcohol blunts alertness and reduces motor co-ordination. People who drive after using alcohol can’t react as quickly when
they need to. Their vision is affected, and may be blurred or doubled. Alcohol alters depth perception, making it hard to
tell whether other vehicles, pedestrians or objects are close or far away. And because alcohol affects judgment, people who
drive after drinking may feel overconfident and not recognize that their driving skills are reduced. Their driving is more
likely to be careless or reckless—weaving, speeding, driving off the road and, too often, crashing.
Alcohol is a depressant drug, which means it slows down your brain and body. Other depressant drugs, including some prescription
drugs such as sedatives and painkillers, affect a person’s ability to drive safely, in a way similar to alcohol. Any drug
that causes drowsiness, including some cough, cold or allergy medications, can also affect a person’s ability to drive safely.
When alcohol and another depressant drug are combined, the effect is more intense and dangerous than the effect of either
drug on its own. When taking prescription or over-the-counter medications, it is wise to consult with your doctor or pharmacist
Stimulant drugs, such as caffeine, amphetamines and cocaine, may increase alertness, but this does not mean they improve driving
skills. The tired driver who drinks coffee to stay awake on the road should be aware that the stimulant effect can wear off
suddenly, and that the only remedy for fatigue is to pull off the road and sleep. Amphetamines do not seem to affect driving
skills when taken at medical doses, but they do make some people overconfident, which can lead to risky driving. Higher doses
of amphetamines often make people hostile and aggressive.
People who use cocaine are also likely to feel confident about their driving ability. But cocaine use affects vision, causing
blurring, glare and hallucinations. “Snow lights”—weak flashes or movements of light in the peripheral field of vision—tend
to make drivers swerve toward or away from the lights. People who use cocaine may also hear sounds that aren’t there, such
as bells ringing, or smell scents that aren’t there, such as smoke or gas, which distract them from their driving.
Cannabis and other hallucinogens
Cannabis impairs depth perception, attention span and concentration, slows reaction time, and decreases muscle strength and
hand steadiness—all of which can affect a person’s ability to drive safely.
The effects of hallucinogenic drugs, such as LSD, ecstasy, mescaline and psilocybin, distort perception and mood. Driving
while under the influence of any of these drugs is extremely dangerous.
What is blood alcohol content?
When you drink alcohol, it goes directly from your stomach into your bloodstream. Blood alcohol content (BAC), or percentage
of alcohol in your blood, can be measured by police with a breathalyzer or blood test.
Under provincial laws in the Ontario Highway Traffic Act, driving with a BAC of .05 to .08 (known as the “warn range”) can
result in a licence suspension of three days for a first offence, seven days for a second offence or 30 days for a subsequent
offence. The Criminal Code of Canada sets the “legal limit” for drinking and driving at .08 BAC. Ontario drivers with a level
one or two graduated licence must maintain a zero BAC.
Because people react differently to the effects of alcohol, it is very difficult for a person to judge his or her own BAC.
A person may not feel “drunk,” but may still be legally impaired.
Is there some way I can quickly “sober up” if I’ve been drinking and need to drive home?
No. Once a person consumes alcohol, it enters the bloodstream, and only time can reduce the concentration of alcohol in the
blood. It takes about an hour for the average human body to process and eliminate two-thirds of the alcohol in one standard
drink. This rate is constant, meaning that the more you drink, the longer time you need to wait before driving. Drinking coffee
or other caffeinated beverages might make you more alert, but your ability to drive will still be impaired.
How many crashes involve drivers who have been drinking alcohol or using other drugs?
Impaired driving is the largest single criminal cause of death and injury in Canada. In an average year, more than 1,200 Canadians
die as a result of impaired driving and more than 71,500 are injured.
Young people who drink or use other drugs and drive may be particularly at risk for being involved in a motor vehicle accident
because they have less experience with driving, and are more likely to engage in risk-taking behaviour.
Who are the people who drink and drive?
Studies have found that people who have been convicted of impaired driving offences come from many different backgrounds,
age and income groups. Such studies have also identified certain characteristics of people who drink and drive. Looking at
convicted drinking drivers, we see that:
- most are male
- a high proportion are “heavy” drinkers
- many have an “antisocial attitude,” meaning they lack respect for the law and the safety of others
- of those who are convicted of drinking and driving, almost all report having driven while under the influence many times before.
What are we doing to reduce impaired driving?
As of May 2009, driving with a “warn range” BAC of .05 to .08 in Ontario can result in a licence suspension of three days
the first time, seven days the second time or 30 days each subsequent time.
Impaired driving of any vehicle (including boats) is a criminal offence with strict penalties under federal and provincial
law. These penalties include suspension of the driver’s licence, fines, jail sentences, a treatment or education program,
and a period where the person may only drive a vehicle that is equipped with an ignition interlock device. This device prevents
a vehicle from starting if a driver’s BAC measures above a pre-set limit.
The term “impaired” refers to not only the effects of alcohol, but also other drugs. More charges are laid for impaired driving
offences, and more court resources are devoted to the prosecution of these charges, than any other offence in Ontario.
Drivers who either fail or refuse a breathalyser test can be charged. In Ontario, a charge of driving with a BAC over .08
or refusing to provide a breath sample brings an automatic 90-day suspension of the driver’s licence at the time the charge
Penalties for impaired driving convictions vary depending on the number of times a person has been convicted of that offence:
- A first conviction results in a $1,000 fine, the suspension of the driver’s licence for one year and, once the driver’s licence
is reinstated, a minimum one-year ignition interlock condition.
- Penalties for a second conviction include 30 days in jail, a three-year driver’s licence suspension, and a three-year ignition
- A third conviction results in 120 days in jail and a lifetime suspension of the driver’s licence (which can be reduced to
10 years if certain conditions are met).
- With a fourth conviction, there is no possibility of the person ever having an Ontario driver’s licence again, and he or she
must spend another 120 days in jail.
People who are caught driving while their licence is suspended will have the vehicle impounded (whether or not they are the
actual owner) and face stiff fines.
In addition to these penalties, any person in Ontario who has been convicted of impaired driving, or who has had two or more
“warn range” licence suspensions for driving with a BAC of .05 to .08, must pay for and complete “Back on Track,” an alcohol
education or treatment program.
Some laws regarding impaired driving apply to people who serve alcohol, whether in a public place, such as a restaurant or
bar, or in a private home. For example, if you had a party, and one of your guests drove away after drinking too much and
caused an accident, you could be sued for damages. Everyone who serves alcohol has the responsibility to ensure that his or
her patrons or guests do not get behind the wheel after drinking too much.
Other measures to prevent and control drinking and driving include widespread public awareness campaigns and the RIDE (Reduce
Impaired Driving Everywhere) program, which allows police to stop drivers to check for alcohol use.
Physicians who have reason to believe that a patient may not be able to drive safely due to a medical condition—such as a
serious alcohol problem or alcohol dependence—must, by law, notify the Ministry of Transportation. The Ministry may suspend
the driver’s licence indefinitely, pending a review by a substance use professional.
Are people more cautious about drinking and driving than they used to be?
The number of people who drink and drive in Ontario has declined steadily over recent years, from 13 per cent in 1996 to six
per cent in 2009. More people are taking the role of “designated driver” and choosing not to drink alcohol when they know
they will be driving. Others prefer leaving the car at home, and taking a cab or public transit. While this trend seems to
reflect the positive effect of increased public awareness and stricter laws, drinking and driving continues be a major cause
of injury and death.