Couple In The Road

A truck driver was going down a steep incline when, at the foot of the hill, he was able to make out a couple having sex in the middle of the road. Five times on his descent he sounded his horn, but they didn't move. He finally brought the truck to a halt inches from them. The truck driver got out and stormed:
"What the hell's the matter with you two? Didn't you hear me? You could have been killed!"
The man replied nonchalantly: "Listen, I was coming, she was coming, and you were coming. You were the only one with brakes."