Police forces in Great Britain are a step closer to having a new device to test drivers for drugs.
Ministers say the so-called "drugalyser" will be used in a police station and will remove the need for a doctor, making the process quicker.
It will take a mouth swab and analyse it for traces of cannabis, cocaine, amphetamines, heroin or methadone.
The Home Office has published the specification for the technology and is looking for manufacturers.
At the moment police first need a doctor to decide whether the suspect has a "condition which might be due to a drug", and then a blood test has to be carried out.
Getting a doctor to the police station and the examination itself both take time - and could mean the drugs have left the suspect's system before the blood sample is taken.
Under the new plans, police will still have to rely on so-called impairment tests which require drivers to carry out basic tasks such as walking in a straight line at the roadside.
But if a suspect is arrested, they will be able to be tested with the new device at a police station.
If the test is positive, a blood sample will then be taken by a custody nurse. Evidence to support a prosecution can only come from a blood specimen.
Crime Prevention Minister James Brokenshire said motorists under the influence of drugs "were a danger on the road".
"We are determined that police have the highest quality devices to help identify them. This specification is a big step towards that goal," he said.
Road Safety Minister Mike Penning said: "Drug drivers show a flagrant disregard for the law and put the lives of responsible motorists at risk.
"This announcement means that we are a step closer to making sure the police have the equipment they need to tackle this selfish minority more effectively and make the roads safer for everyone."
National road safety charity Brake welcomed the latest development but said the law must change.
At present, police must have evidence that a person's driving has been impaired by the drugs in their system, whereas anyone caught over the legal alcohol limit can be prosecuted on that fact alone.
Campaigns officer Ellen Booth said: "There still isn't a law making it an offence to drive on illegal drugs. Without this legislation, the police have to try to prove driver impairment, which is difficult and helps to explain why there are so few convictions."
Manufacturers have until the end of January to indicate whether they are interested, and testing of the devices is due to begin in February.
The development of the new device follows the publication of a review into the problem of drug-driving last June.
The review, by Sir Peter North, concluded the drug-driving problem was "out of all proportion" to the official figures - partly because of the difficulty in testing for drugs, which means many cases go unrecorded.
In August 2010, the government said the device could be rolled out across all police forces in England, Scotland and Wales within two years.
Work is also continuing on a roadside version.