A first-of-its-kind survey released Monday revealed a surprising number of California drivers are operating vehicles under the influence -- not of alcohol -- but drugs.

The new survey from the California Office of Traffic Safety found 14 percent of 1,300 drivers tested positive for drugs that impair driving, including prescription, over the counter and illegal drugs.

7.3 percent of drivers tested positive for for alcohol, but the most the most prevalent of drugs was marijuana at 7.4 percent.

Santa Clara County tests drivers for marijuana and combined with a sobriety field test.

"The blood tests will show you have active THC in your blood, which is what we're testing for with marijuana," said Santa Clara Sounty's Supervising Deputy Distirct Attorney James Gibbons-Shapiro. "We're going to be able to show that the marijuana was impairing your ability to drve safely, even though its not at a specific level. "

The Office of Traffic Safety says drug impaired driving is often under reported and is hoping better training of officers and more resources for prosecutors will help address the problem.

San Jose Police say officers have to be more detailed in their reports if they suspect drugged driving. They also need to rely on what they call objective observations of drug use.

"Whether or not they have droopy eyelids, if they're constanly licking the lips or nervous activity. There are a lot of objective symptoms of drug influence," said Sgt. Jason Dwyer.

Governor Brown just signed a new law making each DUI category -- alcohol, drugs and alcohol plus drugs -- into separate sections of the vehicle code.