Driving into a prison parking lot, in all the places I've read about, makes your car open for searches. Don't have a cell phone on you, or a butter knife in your picnic basket! If your deer rifle is in the trunk, FSM help you. The guards might consider you a security threat unless you fit into a category they understand, such as "employee" or "volunteer". If you're there to visit a prisoner, it depends on the place, but some will treat you like an inmate, so you'd be driving into a situation of people prepared to assume the worst.
(regular user mode)Please don't ask about jwhouk's workplace. He hates to talk about it and right now has compelling reasons not to talk about it.(/)