Wife and I, while teenagers dating, got busted by the cops once in a day-use-park.
Some asshat (although I understand now why they did it) called in a "woman in distress" - I was handcuffed, naked, and thrown in the cruiser while my hysteric girlfirend tried to convince the cop we were just teens willingly fucking.
I was eventually let go, we were told to "get a fucking room" and he took off. So we finished what we started in the backseet
As to comfort....its not. Car sex IMHO is the lowest form of sex life, only desireable for (a) exibitionism or (b) lack of any other choice