Senior supervisor of highway patrol's Riverina cluster, acting Senior Sergeant John Aichinger said ice was the main illegal drug detected, followed by cannabis.

"I think you will find that Sydney is in the grip of an ice epidemic, and Wagga is no different," Sergeant Aichinger said.

"We are no worse than Sydney, and no better.

"We are following a trend found in other places.

"Ice is very prevalent."

In Wagga Local Court on Wednesday, 13 people were on the criminal list charged with driving with an illicit drug in their system.

Sergeant Aichinger said he thought those people were among those caught in a June blitz during which 48 drivers out of 600 tested positive for illegal drugs.

The number of people being charged is likely to rise at least in the short-term as the state government rolls out more drug detection machines.

"We are getting better technology, and we are also getting it deployed to (police) stations," Sergeant Aichinger said.

Most testing now is conducted with machines in four or five buses that move around NSW.

Sergeant Aichinger said drug testing would become as common as random breath tests (RBT) for alcohol.

And he thinks that just like after the introduction of random breath tests for alcohol, the number of people caught with drugs in their system will grow but then decline as people get the message they are likely to get caught.

"When you look back to before RBT came in, a lot of people thought they could drink and drive and not get caught.

"I think it's the same today with illicit drugs."

Sergeant Aichinger said illicit drugs could be detected in a person's system a number of days after being consumed.

"Everyone is different, but up to three or four days is a window where you could get caught," he said.

"The first statement is don't use these drugs.

"They are manufactured in back yards and sheds.

"You don't know what is in them.

"They are harming your body and effectively killing you.

"If you are silly enough to use them expect to be caught."