One in 20 people who admit to drinking and driving also take illegal drugs before getting behind the wheel, a survey has suggested.
Suspect motorists face roadside tests
The more alcohol consumed, the greater the likelihood of drug driving, the survey from Green Flag Motoring said.
Its findings follow a Christmas police campaign in north-east England.
"Smoking one cannabis joint has the same effect on drivers' reactions as several pints of beer," a Durham police spokesman claimed.
Chief Inspector Paul Goundry added: "Younger drivers
do not realise the dramatic effect drugs can have on their driving."
Dr Rob Tunbridge, head of impairment studies at transport research body TRL, said there had been a "a six-fold increase in illicit drug use since the 1980s".
He said drug driving "significantly increases your chances of
being killed or seriously injured in a crash".
"It is not worth the risk."
Green Flag spokesman Nigel Charlesworth said a growing hardcore of drivers "insist in taking high-wire risks with theirs and our lives".
"Whatever the drug, the
effects are always unpredictable," he added.
Road safety charity Brake chief
executive Mary Williams called for action "to tackle the anti-social minority whose potentially lethal actions seriously threaten the lives of other innocent road users".
"It is deeply disturbing to find some drivers prepared to ignore the message driving whilst impaired can be fatal."
Drug driving showed "a woeful disregard for human life", Ms Williams said.
"Never take illegal drugs and drive."