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Legal guide to UK motoring, sections for law enforcement, Driver licensing, learner and new drivers, buying and selling, speeding fines, owning a vehicle, wheel clamping, traffic information.



It is an offence to drive whilst unfit through drugs. Many people think that if they drive under the influence of drugs, a vehicle search and a potential charge of possession is all they have to be worried about.

Police are on the look out more than ever and aside from just the erratic behaviour know all the signs to spot a drug driver.

Drug drivers may think that just because they pass a test for alcohol they will be off the hook. This is not the case because the police can also prosecute a driver who is unfit through drugs and there are various ways they can detect and prove the offence.


The consequences of a drug drive conviction are devastating and far reaching. The penalties are the same as for drink driving.

Taking drugs will impair driving skills. Driving whilst under the influence of drugs is extremely dangerous and can affect driving in numerous ways.

Prescription or over the counter medicines should always be taken properly. Advice about this is provided on the packaging and in the patient information leaflet supplied and packed in with the medicine. Advice can also be obtained from whoever has prescribed the medicine, or from the pharmacist who dispenses it.

Driving whilst under the influence of drugs

Changes to the drug driving law

On 2 March 2015, the drug driving law changed to make it easier for the police to catch and convict drug drivers.

It is now an offence to drive with any of 17 controlled drugs above a specified level in your blood. This includes illegal and medical drugs. The limits set for each drug is different, and for illegal drugs the limits set are extremely low, but have been set at a level to rule out any accidental exposure (i.e from passive smoking).

Officers can test for cannabis and cocaine at the roadside, and screen for other drugs, including ecstasy, LSD, ketamine and heroin at the police station. Even drivers that pass the roadside check can be arrested if the police suspect that your driving is impaired by drugs.

The consequences

The penalties for drug driving are the same as for drink driving. If you are convicted you could face: • A minimum 12-month driving ban
• A criminal record
• An unlimited fine
• Up to 6 months in prison
• An endorsement on your driving license for 11 years
The consequences of a drug drive conviction are far reaching and can include: • Job loss
• Loss of independence
• The shame of having a criminal record
• Increase in car insurance costs
• Trouble getting in to countries like the USA
As with drink driving, repeat offenders will be dealt with swiftly and more severely. A repeat offender will face a much longer ban from driving, if offense has resulted in a death this could mean loosing your license permenantly. This will also result in a longer prison sentence, which can be anything up to 10 years.

Driving under the influence of drugs - whether prescribed medication or illegal substances - is just as dangerous as driving when drunk. It's also against the law. Drugs can affect your mind and body in a variety of ways that mean you aren't able to drive safely. Not only that, the effects can last for hours or even days.

The police can carry out roadside tests of impairment to help them decide whether to arrest you if they think you are unfit to drive through drugs.

Different drugs will effect your driving in different ways. Some will make you tired and unable to control a car, while others will make you far too over confident. Many drugs stay in your body for days and weeks afterwards. Driving home the day after taking drugs is just as dangerous. The day after, your body will be confused, dehydrated and fatigued. You may feel sick and suffer from dizziness or tremors.

Effects of different drugs on driving

Information about the effects of drugs in driving populations has been studied through a combination of laboratory based behavioural studies, on-road driving studies, and epidemiological study. However, there are ethical constraints which limit such studies. Review of the literature173 allows a summary of the main illicit drugs which cause impaired driving most commonly.


(marijuana) is a unique drug, having both hallucinogenic and central nervous system depressant properties. In on-road driving experiments, difficulty in maintaining lane position (weaving) and headway were noted with a trend towards increasing impairment with increasing dose.

Other reported effects of marijuana on driving ability include inattention, poor coordination, slowed reaction time and increased error rates in complex tasks. When combined with alcohol, the effects appear to be considerably greater than would be expected by each substance’s effect working alone. This includes a decrease in visual search activity, changes in reaction time, and increased driving out of lane.


Stimulants, which include amphetamines, metamphetamine and cocaine, produce a range of effects on drivers that differ in the acute phase (shortly after drug consumption) from the post-acute phase, when drug withdrawal or abstinence syndrome can be an issue.

The immediate effects of stimulant use produce intense excitement and euphoria, which can be distracting and disorienting, affecting the degree of attention and concentration on driving. The drugs also produce changes in reaction time, often resulting in faster but less reasoned and more impulsive responses, and increased risk taking. At low doses, stimulants can offset fatigue and delay the need for sleep (which may be of some short-term benefit for a driver), but when abused the chronic sleep loss resulting from binge use creates a rebound or withdrawal effect when drug use stops.

Central nervous system depressants

This category includes drugs such as benzodiazepines (for example, diazepam and temazepam), sedative hypnotics used as ‘sleeping tablets’, some antidepressants, muscle relaxants and some antihistamines. This category is the most challenging to discuss, because most of these compounds have legitimate therapeutic uses, and in many cases a driver treated with an impairing drug, for example, a driver successfully treated for depression with an antidepressant, is often a better driver than an untreated driver.179 Benzodiazepines, while a legitimate medicine, are frequently either misused as such or are used as a drug of abuse. In terms of impairment, the central nervous system depressant-impaired driver has difficulty maintaining lane position, drives too fast or too slowly for conditions, fails to obey traffic signals, and is involved in crashes through lack of sustained attention and slow reactions. Recent research has concluded that benzodiazepine users are at a significantly increased risk of crashes compared to nonusers, and these differences may be accounted for by a difficulty in maintaining road position.180 This increased risk of crash appears to be highest during the first few weeks of use.

Narcotic analgesics

The narcotic analgesics include the drugs heroin and morphine (used commonly for relief of severe pain).

Tolerance to the effects of opioids is well documented, and there is some evidence that people who become stabilized on moderate doses of opioids have tolerance to some of the impairing effects of these drugs.

However, recreational use or abuse of opiates generally involves the use of doses which defeat any offset for tolerance. The euphoric intoxicating effect of opioid abuse is inherently inconsistent with safe driving.

There is a specific marker (6-monacetylmorphine) which can differentiate between use of morphine, and heroin abuse.

Hallucinogens, dissociatives and inhalants

Hallucinogens, dissociatives and ‘inhalants’ are drugs which create associations in the mind resulting in an altered perception of reality. ‘Inhalants’ are a broad range of substances whose volatile vapours are taken in via the nose and windpipe. Common ‘inhalants’ of abuse include glue and acetone (nail varnish remover).

Hallucinogens, dissociatives and ‘inhalants’ are highly debilitating, and interfere with a person’s normal daily activities to the extent that driving is not just impaired, but is impossible; consequently, they are less frequently encountered in arrested or deceased drivers.

Priority drug classes identified as being detected in driving populations

As described, there is a wide variety of substances (both licit and illicit) that can negatively affect the skills and abilities necessary to operate a vehicle safely which makes their listing a challenge. It appears, on the basis of the synthesised research evidence, that the drugs or classes of drugs of most concern which are associated with impairment of driving and more commonly abused (rather than used under medical supervision) are:
• opiates;
• amphetamines;
• methamphetamine;
• ecstasy (MDMA);
• cocaine;
You're unable to safely control your car using your steering wheel, so your car may wander across the road.

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