Cocaine and cannabis are the headline substances police are testing for, but the government has been intentionally vague about the entire range of narcotics it will be watching except to say it won't only be illegal drugs; anxiety drugs, prescription painkillers, sleeping pills are being measured, and word is that they're trying to develop a protocol for dealing with so-called "legal highs" or "club drugs," which are legal substances that can be abused. The government also said that officers don't have to tell you which test they're administering, but refusing the drugalyzer test gets you prosecuted the same as if you'd refused a breathalyzer.
The law making "drug driving" a criminal offense doesn't take effect until March, but the testing is underway now. Estimates put drug-driving deaths at 200 deaths a year, but the haphazard testing suggests the real number is higher and that hose caught are 50 times less likely to be convicted than those caught for drunk driving. Said Policing Minister Mike Penning, "The Government is determined to drive this menace from our roads."