O'FALLON, Ill. —

Recreational marijuana may now be legal in Illinois, but that also means police departments across the Bi-State will be cracking down on buzzed driving.

"We’re planning to see an increase in DUI cannabis," says Officer Joseph Wagner with O'Fallon, Illinois Police. "We’re trained to come in and do this 12 step process to check vital signs like pulse, blood pressure, body temperature, pupil size."

He's one of three O'Fallon Police who are extensively trained as a drug recognition expert.

"We’re able to, with near certainty, determine what drug category that this person is either impaired by and it will also rule out medical conditions as well," says Wagner.

All police officers have enough training to conduct a field sobriety test, and can arrest you for a DUI just like if you were suspected of drinking.

Wagner says the only real difference between screening for drugs and alcohol, is there is no breathalyzer equivalent for marijuana.

So in those cases, officers must use their training and gut instinct. This is the advice he gives his officer.

"If you don’t feel comfortable letting them drive, and they’re too impaired to drive, then they’re too impaired to drive. They’re impaired by something," he says.

Like alcohol sales, after the arrest, you will have to submit a blood or urine sample to confirm anything is in your system, which could result in charges.

"The problem is, it’s affecting other parts of your brain as well. Depth perception, cognitive ability, the ability to make split-second decisions," says Officer Wagner.

He says the perception that marijuana is harmless isn't true, especially when you're behind the wheel.

"If you feel different, then you drive different. That’s my message," he says.

Impaired driving isn't the only thing officers could bust you for.

They're also on the lookout for how you transport what you bought from a dispensary.

By law, all marijuana products must be in airtight, childproof and scent-proof bags while you're in the car, otherwise, you could be liable under open container laws.

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