They will target people who have used cannabis and methamphetamines at nightclubs and dance parties.
Truck drivers who take drugs - usually methamphetamines - to stay awake will also face scrutiny.
A media officer at Victoria Police, Sheree Argento, said these two drugs were being focused on because "obviously, they are the two most accessible drugs, and the two that people are most likely to take and then drive".
The test involves asking drivers to place a small absorbent pad on their tongues for a few seconds.
The screening of saliva will not detect prescription drugs or medication such as cold or flu tablets.
Drivers testing positive will then be required to give a second sample, which will be sent to a laboratory.
