New rules intended to crack down on those driving under the influence of drugs come into effect from today.
Legal limits have, for the first time, been laid out for eight illegal and eigh prescription drugs - with motorists to be prosecuted if they are found to have exceeded them.
It will effectively mean a zero tolerance policy for anyone caught under the influence of heroin, cocaine and cannabis.
Police will be able to use "drugalysers" to screen for cocaine and cannabis at the side of the road, while it will also be possible to test for drugs such as ecstasy, LSD, ketamine and heroin at a police station.
People using prescription drugs - including morphine and methadone - will not be penalised if they use the drugs within the recommended amounts.
The new rules have been welcomed by campaigners, including the mother of a 14-year-old girl who was killed by a speeding driver on cannabis.
Lillian Groves died outside her home in New Addington, Surrey in June 2010, with the driver handed an eight-month prison sentence.
Her family then mounted a campaign known as Lillian's Law, which saw a 22,000 name petition handed to Downing Street in 2013.
The limits are as follows
- Benzoylecgonine: 50µg/L
- Cocaine: 10µg/L
- Delta-9-tetrahydrocannibinol (cannabis): 2µg/L
- Ketamine: 20µg/L
- Lysergic acid diethylamide:1µg/L
- 6-monoacetylmorphine (heroin): 5µg/L
- Amphetamine: 250µg/L
- Clonazepam: 50µg/L
- Diazepam: 550µg/L
- Flunitrazepam: 300µg/L
- Methadone: 500µg/L
The penalties for drug driving under the new laws will be:
- A minimum one-year driving ban
- A fine of up to £5,000
- Up to six months in prison
- A criminal record
- A mark on driving licence lasting for 11 years