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A to Z of Drugs: Amyl Nitrate | Anabolic Steroids | Cannabis | Cocaine | Crack | Ecstacy | GHB | Heroin | Ketamine | LSD | Magic Mushrooms | Solvents | Speed | Tranquillisers


Effects of Drugs


Cannabis is a relaxant (mild sedative) and may reduce your ability to react quickly in pressurised situations. It is also a mild hallucinogen and can make you unsteady and blur your vision. Drivers can have a lack of concentration and poor hand and eye co-ordination.

The drug has a very similar effect to alcohol and the stronger effects usually last roughly two to four hours. However if eaten or a stronger type, 'skunk', is used, the effects can be more powerful and last longer.

At times there can be a feeling of euphoria, replaced later with drowsiness. If mixed with even a small amount of alcohol the effects of cannabis can increase dramatically - you can feel completely disorientated.

Traces of drugs can still be detected in your system for weeks after being taken.


Cocaine is a stimulant which falsely heightens your perception of light and sound. It has a very similar effect on driving as ecstasy - a feeling of invincibility and euphoria.

Taking cocaine will affect your driving in a number of ways. It can make you feel very alert during the first hour but as the effects wear off the chances of falling asleep at the wheel are high - even the day after! The effects of 'crack' are much quicker, with an immediate high for about two minutes and the effects lasting around 10 minutes.

In addition to over confidence, increased risk taking and distorted perception, cocaine can increase feelings of paranoia and create erratic behaviour.

If mixed with other substances, such as alcohol, the effects of cocaine and driving can be potentially lethal.

The incidents of cocaine being found in victims of car crashes are becoming more common.


Ecstasy is a stimulant drug, this time with hallucinogenic properties, which can distort vision and heighten sense of sound. Your concentration is affected and your awareness of road dangers is significantly decreased.

Effects can last approximately three to six hours, but they can last longer depending on the person, followed by a gradual comedown. It can give you a feeling of euphoria and an increase of energy but as the effects wear off you can feel fatigue and severe tiredness, making driving dangerous.

Ecstasy can give you a feeling of 'invincibility' which changes your driving, making you over confident, aggressive and more likely to take risks on the road. You may well think you are a better driver than you actually are.


Heroin is a very strong pain killer and slows reactions, dulls perceptions and affects coordination. You often feel sleepy, sluggish and can't control the car resulting in a crash.

Although you may feel euphoric it can also cause distorted perception, nausea and breathing problems. The effects take anything up to 24 hours to reduce.

It is widely agreed that someone heavily under the influence of heroin will be unlikely to be in any fit condition to attempt to drive.

The numbers of drivers found with heroin in their blood after a road traffic fatality are said to be increasing.


LSD severely distorts senses and perceptions creating visual hallucinations and making you feel detached from reality. It can result in serious injury or even death - without even getting behind the wheel!

Driving after taking LSD is extremely dangerous and the effects can last up to 12 hours. A 'bad trip' can be frightening and you can experience terrifying thoughts and feelings. You may feel confused and distrust your own senses, have poor coordination and control and experience tremors and twitching.

Anxiety can also be increased and flashbacks can also occur, in the following weeks and months.


Speed is a stimulant which can make you feel more awake and alert. You may feel more confident but the effects will create a loss of coordination and make you less likely to react to potential dangers.

The effects can last up to six hours but this varies depending on how it was taken and from person to person. Physical effects include headaches and dizziness as well as irregular heartbeat and breathing. You will often become more irritable, restless and anxious as the effects wear off.

After your initial alertness, this can change to sleeping problems, exhaustion and fatigue, which will also affect your driving.

Prescription Drugs

These can also have a detrimental effect on driving.

Drugs such as temazepam or diazepam taken for depression are cropping up in tests after road deaths. These can cause drowsiness and those taking such tablets are warned against using machinery.

Similarly strong migraine and hay fever tablets can cause a similar drowsiness and a lack of speedy reaction to situations.

If you use these kinds of prescription tablets, you are advised not to drink. Mixing with alcohol can seriously impair driving ability and sometimes cause blurred vision.

All information sourced from