In the Warrnambool Magistrates Court on Monday this week five people pleaded guilty to drug driving, most positive to both amphetamine and cannabis.

The four men and one woman were fined between $750 and $1200 and banned from driving for 12 months.

South-west police road safety adviser Acting Senior Sergeant Gavin Slade said that generally first-time drug driving offenders were issued with an infringement notice and did not appear in court.

"We are seeing a lot more secondary offenders appearing in court, people charged with at least a second offence of driving under the influence of drugs," he said.

"Police statewide are doing a lot more tests and there is now certainly an increased likelihood that any driver will be tested for drugs."

Acting Senior Sergeant Slade said that after Operation Furlong this week, to coincide with the Melbourne Cup carnival there were a number of police road operations planned in the lead-up to and including the busy Christmas/New Year period.

"There's also a focus on significant community gatherings and where the traffic is going," he said.

"With a more flexible rostering system you can see there's real intelligence-based proactive thought process about deploying resources," he said.

"Drug impaired driving is certainly a comparable issue to drink driving.

"There are also issues with drugs being able to stay in a driver's system for a significant amount of time."

It's often quoted in courts that cannabis is capable of staying in a driver's system for up to a month, while amphetamine-based drugs can also be detected a number of days after being used.

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