Starting this weekend, law enforcement in Los Angeles will begin expanded use of saliva swab test kits on drivers suspected of driving under the influence of drugs. The change comes just in time for New Year's Eve celebrations.

The testing is already used at some LAPD DUI checkpoints and at three stations that have jails. A $520,000 grant awarded to the L.A. City Attorney’s Office will expand the regular use of the test next year.

“Using drugs and driving is a combination that won’t be tolerated in this city,” said L.A. City Attorney Mike Feuer.

RELATED: Weekend Traffic: 405 Freeway closure, free METRO rides on New Year's and DUI checkpoints

State law requires drivers suspected of driving under the influence to submit to a blood test but they have the right to refuse the swab. The oral test is voluntary, said deputy city attorney Michelle DeCasas.

So far, 50 people have consented to oral swab tests. But none of the results have been introduced in court because the defendants pled out before the cases went to trial, according to the city attorney’s office.

“We are seeking to have it introduced as an evidential piece in our prosecutions of DUI (cases),” DeCasas said. “But at this point, if drivers elect not to do it, it’s their right not to.”

Bakersfield, Sacramento and Fullerton are also using the oral swab test kits.

Feuer said the rise of medical marijuana dispensaries has led more drivers, including lawful card-carrying users, to get behind the wheel under the influence of the drug.

The oral swab tests can detect tetrahydrocannabinol or THC – the active impairing ingredient in marijuana – that is in a person’s system up to three hours after ingestion.

The city attorney’s office didn’t have statistics on the conviction rate of DUI cases involving drug use. Feuer said his office would keep tabs on the numbers moving forward.

LAPD anticipates making a large number of DUI arrests this New Year’s Eve. Last year, there were 2,087 traffic collisions involving impared drivers and 16 people died in drunk driving traffic accidents, according to the LAPD.

“The holiday season is one of the most egregious times for drinking and driving,” said LAPD Commander Andrew Smith. “If we suspect someone is driving under the influence of narcotics or alcohol, we will make that arrest.”

The LAPD will be conducting several DUI checkpoints this weekend:

Friday, December 27

Checkpoint in the 77th Street Area near Manchester Avenue and Hoover Street from 6 p.m. to 12 a.m.

Checkpoint in West Valley at Roscoe Boulevard and Gloria Avenue from 8 p.m. to 2 a.m.

Saturday, December 28