This thread about perceived lunchtime infidelity made me remember when I saw that first hand.
There's a dam that goes over the Connecticut River right near where my old office used to be. There's some park space there with picnic tables. I used to each lunch there some days when it was nice.
So I pulled in one day and saw only one other car in the parking lot. Looked like a guy just sitting in his car. As soon as I made eye contact, he got this deer in the headlights look. Suddenly I see a woman emerge from below eye level, and they tore out of there.
I told my boss when I got back to the office. I said I can understand the mid-day quickie, but I wondered why they didn't just go home and do that. He said, "What makes you think they're married?"