Find out the legislative and car insurance implications of driving under the influence of drugs - whether they're legal or illegal substances.
Drug driving describes anyone who gets behind the wheel of a vehicle under the influence of any substance, legal or illegal, that's likely to impair their driving ability.
New legislation came into force in England and Wales on 2 March, 2015, to toughen up rules.
It sets limits at very low levels for illegal drugs such as cannabis, cocaine, MDMA, ketamine, benzoylecgonine, methamphetamine, LSD and heroin.
But it also means that drivers taking prescribed and/or over-the-counter medicines are also at greater risk of breaking the law.
The following eight prescription drugs are included under the new legislation:
Drivers are unlikely to be over the specified limit for these medicinal drugs if they've taken normal prescribed doses and their driving isn't impaired.
But motorists who are unsure about the effects of their medication on their ability to drive should seek advice from their GP or pharmacist before getting behind the wheel.
Roadside testing is used to establish whether any of the listed drugs are present, using a device that has been labelled the 'drugalyser'.
New devices that can test for a greater number of drugs at the roadside will be developed in the future.
The roadside test will be followed by a forensic analysis of a blood sample taken at a police station to establish which drug is involved and the quantity in the blood.
An offence will carry a minimum one-year driving ban, a fine of up to £5,000 and a maximum of six months in prison.
Side effects are likely to include greater difficulty in arranging car insurance and a hike in premiums, while potential impacts could include loss of job and difficulty in arranging travel to certain countries such as the USA.
The law doesn’t cover Northern Ireland and Scotland but you could still be arrested if you’re unfit to drive.
The prescription drugs affected by the new law can be used to treat a wide variety of problems.
Clonazepam, for example, is prescribed to treat seizures or panic disorders, while diazepam is used for anxiety disorders, alcohol withdrawal symptoms or muscle spasms.
Flunitrazepam, which is also known as rohypnol, is a sedative that can lead to deep sedation, while morphine or opiates are used to help with pain relief. Methadone is also used for this purpose, as well as being a treatment for heroin addiction.
Convulsions or seizures caused by epilepsy can be treated with lorazepam, oxazepam is used to relieve anxiety, while temazepam affects chemicals in the brain that may become unbalanced and cause insomnia problems.
"Drug driving is an increasing problem and is treated very seriously by the police, the courts and insurers," said Gocompare.com's Matt Oliver.
Motorists convicted of drug driving can expect to see steep increases in their insurance premiums or find difficulty in obtaining cover
Matt Oliver, Gocompare.com
"The penalties for drug driving are the same as for drink driving, ranging from a hefty fine to disqualification or imprisonment.
"Drug drivers not only present a serious risk to themselves but to other road users.
"Drugs, whether they are illegal substances or prescribed medications, can affect both your mind and body.
"Side effects can include slower reaction times, drowsiness, erratic or aggressive behaviour - all of which may impair your ability to drive safely.
"In judging whether someone is fit to drive, no distinction is made between legal or illegal drugs."
"Motorists convicted of drug driving can expect to see steep increases in their insurance premiums or find difficulty in obtaining cover.
"So, if you are prescribed any new medication or you're buying over-the-counter medicines, ask your GP or pharmacist if it will affect your ability to drive.
"Also, always read and follow the instructions provided with your medication. If they advise against 'operating heavy machinery', take it as a warning not to get behind the wheel of a car."