Many drugs affect your brain functioning and some directly affect your driving.
Prescription and over-the-counter drugs
Like alcohol, other depressant drugs include sedatives or tranquillizers (used to treat anxiety, depression and sleeping disorders, e.g., valium), antihistamines (often used in flu, allergy and hay fever remedies) and painkillers. These drugs slow down your brain and body; they blunt alertness and reduce motor coordination. This affects a person's ability to drive safely in a way similar to alcohol. Any drug that causes drowsiness can also affect a person's ability to drive safely.
People who drive after using any type of depressant can't react as quickly when they need to. Their vision is affected, and may be blurred or doubled. Depth perception is altered, making it hard to tell whether other vehicles, pedestrians or objects are close or far away. Their driving is more likely to be careless or reckless – weaving, speeding, driving off the road, and (too often) crashing.
If the label advises against operating heavy machinery, consider it a warning not to get behind the wheel of a vehicle.
Stimulant drugs, such as caffeine and amphetamines, 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 over-confident, which can lead to risky driving. Higher doses of amphetamines often make people hostile and aggressive.
If you think drug taking has little, or even a positive impact on your driving, you could be tragically mistaken. It's important to bear in mind that it can be hard to determine exactly how a drug will affect your driving ability – impairment caused by drugs can vary according to the individual, drug type, dosage, the length of time the drug stays in your body, or if the drug has been taken with other drugs or alcohol.
When taking prescription or over-the-counter medications, it is wise to consult with your doctor or pharmacist before driving.
Illegal drugs impair your driving. They can alter your perception of time and what you see. They can make you hallucinate or miss things you should see. They can put you to sleep.
Some people think that marijuana is a safer substitute to drinking, but it can cause concentration to wander, which can affect reaction times. It can also cause paranoia, drowsiness, distorted perception and a sense of disorientation – all of which could cause you to lose control at the wheel.
Marijuana is the most commonly traced drug in drivers. Even though the effects fade after a matter of hours, it can be detected in the blood for up to four weeks. In theory, this can compromise the driver if they tested positive, even if their driving wasn't adversely affected at the time.
Some experts claim that smoking a marijuana joint has roughly a similar level of impairment on driving ability as drinking four pints of beer. Also, reports show that in the majority of fatal collisions where marijuana has been detected in a driver’s body, alcohol has also been detected. Alcohol alone or in combination with marijuana increases impairment, collision rate and collision responsibility (the same can be applied to other drugs too).
This is a psycho-stimulant that can lead to misjudging driving speed and stopping distances. It can also cause a distorted sense of light and sound and a feeling of overconfidence, which can lead to aggressive and erratic driving. While it can make you feel alert at first, the effects wear off quickly, leading to an increased danger of falling asleep at the wheel.
A stimulant drug with hallucinogenic properties, ecstasy can distort your sense of vision and heighten your sense of sound. Your concentration can be affected, while you may become over-confident and more likely to take dangerous risks.
Ketamine, LSD and magic mushrooms
Drugs such as these with hallucinogenic properties can strongly influence the senses, so drivers may react to objects or sounds that aren't there and place themselves and other road users in danger. Coordination skills are likely to be greatly affected, and you may experience anxiety, blurred vision and a sense of detachment from reality – all of which could be deadly on the road.
While amphetamines might give you a sense of heightened alertness and confidence, they can be highly dangerous for drivers as they distort your perceptions and can make you feel anxious, prone to panic attacks and lose coordination.
Drug-impaired driving is considered as serious an offence as alcohol-impaired driving, and carries the same penalties.
There are no illegal drugs that improve your driving. They all make it worse. Do not drive after using any drugs.