Police officers using new roadside drug testing equipment made an arrest on they first day they started used their new kit.
New legislation introduced on Monday makes drug driving subject to the same penalties as drink driving.
To catch motorists under the influence officers have been issued with new equipment, similar to alcometers, which detect alcohol in breath, to screen people for drugs.
Officers using the new equipment arrested a 31-year-old on the A1 in Doncaster at 6.30am on Monday.
A South Yorkshire Police spokeswoman said: “On speaking to the man, officers suspected he may have taken an illegal substance and he was tested at the scene with the new drug screening kit.
“The kit returned a positive result for cannabis and the man was arrested under the new legislation, on suspicion of driving while over the prescribed limit, and taken to Doncaster police station where a blood test was taken.
“He has been bailed until April pending the results of the blood test.”
All roads policing officers have been trained on how to use the new equipment.
Chief Inspector for Roads Policing, Glen Suttenwood, said: “It has previously been challenging for officers to determine at the roadside if someone is under the influence of a drug.
“Stopping a driver who you suspect may be under the influence of alcohol is relatively simple to determine either immediately by the smell or by using an alcometer kit.
“However to test for drugs, we have only been able to rely upon impairment tests, which include asking the driver to complete a series of tests and questions, for example walking in a straight line, to assess their capability to drive.”