Police have defected more than 20 cars in four hours of driver testing on the Princes Highway at Monteith.
Officers from the Murray Mallee, highway patrol and police dog operations divisions set up at the Monteith weighbridge between 10am and 2pm last Thursday, accompanied by staff from the National Heavy Vehicle Operator.
They stopped 960 vehicles for random breath tests, and also conducted 60 drug tests.
Three drivers tested positive to drugs, and police confiscated three quantities of cannabis and handed out five drug-related fines.
One motorist was reported for drink driving after allegedly returning a blood alcohol reading of .082.
Sixteen drivers were given on-the-spot traffic fines.
Police will be out in force over the Easter break and school holidays to ensure the safety of all road users.