According to the police report, obtained by TMZ ... 29-year-old Ownbey -- who's been Miss Howard Stern since 2002 -- hit another car on the streets of Chattanooga, Tennessee sometime after 10pm on October 8.

A cop who happened to be in the area, claims he heard the accident and rushed to the scene -- only to find Ownbey in her car ... reeking of booze ... and fumbling to put her cell phone back together.

In the report, the cop states, "[Ownbey] was not aware that she had been in a traffic crash."

The officer claims Ownbey admitted to drinking two glasses of wine before getting behind the wheel ... so he administered a field sobriety test ... and she bombed.

And to make matters worse, cops say they found a small baggie of weed in the car ... as well as a weed pipe and a variety of prescription drugs.

According to the police report, Ownbey was transported to a nearby hospital -- where she took a breathalyzer test ... and blew a .178 ... way over the legal limit, .08.

Once she was medically cleared, Ownbey was taken to a nearby jail where she was booked for DUI, possession of drug paraphernalia, possession of a controlled substance and driving while in possession.

We also spoke with the driver of the car Ownbey hit who tells us Andrea came "flying out of nowhere" and rear-ended him HARD. The driver says his Jeep was totaled in the wreck.