More than half of people stopped for drug driving tested positive for illegal substances, according to South Yorkshire Police.
Officers have tested 118 motorists across the region since new drug driving laws were introduced in March and 61 tested positive for drugs such as cocaine and cannabis.
Dr Alan Billings, the Police and Crime Commissioner for South Yorkshire, has welcomed the results.
He said: “It is obvious from these results that there is a problem of people driving while under the influence of drugs that is as serious as those driving after drinking. If anyone believes that drugs will not be detected, they are much mistaken.”
The new drug screening kits are similar to breathalysers and were introduced following new law that came in on March 2.
Dr Billings said: “Drivers who use drugs should realise that drugs such as cannabis and cocaine will now be detected at the roadside and prosecutions will follow.
“We are determined in South Yorkshire to take off the roads those who put lives at risk whether through alcohol or drugs.”
Only five per cent of those stopped on suspicion of drink driving prove positive, but more than half of those stopped for possible drug use are found to be positive.