Drunk driving won't be the only problem on San Diego’s streets and freeways, this New Year's Eve.

With marijuana legal for all California adults for the first time at midnight Sunday, law enforcement will be watching for “D-U-I-D’s”, or Driving Under the Influence of Drugs.

In Oceanside, police will partner with other law enforcement agencies to stop impaired drivers and help save lives. Oceanside Police Sgt. Rick Davis said in the ten years from 2005-15, the percentage of drivers in fatal crashes with an impairing drug other than alcohol in their system has risen from 26.2 percent to 42.6 percent.

Local and state law enforcement is confronting this problem by training more officers in Advanced Roadside Impaired Driving Enforcement (ARIDE) and Drug Recognition Evaluation (DRE). Those trainings help identify what substances other than alcohol have impaired a driver, and how seriously those motorists are impaired.

Drivers impaired by cannabis and other legal and illegal drugs face arrest and prosecution, just like alcohol-impaired drivers.

“It has taken more than 35 years to convince the vast majority of the public that driving under the influence of alcohol is dangerous, illegal, and socially unacceptable, “ said Rhonda Craft, director of the state Office of Traffic Safety. “We can’t afford to take that long when it comes to driving under the influence of marijuana, prescription medications and illicit drugs.”

Clark Smith, M.D., a San Diego psychiatrist and addiction medicine specialist, said "driving while drugged" is just one potential problem with legal marijuana.

"Any baby-boomer who thinks it's a harmless substance, if they haven't had the THC levels of marijuana that are available today, they really don't know what they're talking about," said Smith, who cautioned that some cannabis users will become dependent on, or addicted to, the drug.

Smith said cannabis will also be a “gateway drug” for a percentage of users, who will move on to narcotics and other dangerous, highly-addictive drugs.

Smith said teens and pre-teens are especially at-risk if they experiment with California's newest legal drug.

"They don't know how to use it,” Smith said. “They use too much. They use it in combination with something else. Kids in junior high are at the highest risk for drugs like this."

Poison control centers are also warning cannabis users to keep those products -- especially cannabis-infused candies, cookies and other edibles -- away from children.

You must be an adult -- 21 years old -- to buy, possess and use marijuana, for non-medical purposes in California as of January 1.

The law also allows adults to grow up to six plants, for personal use.