She could probably tell getting him hard wasn't that difficult, he was already well on his way there, and he grinned as he put his eyes to the road once more, pushing his fingers up along her thigh and towards her crotch, where he began to rub through whatever panties she was wearing that night, groaning as he felt the wetness already there.
He gave her a quick look, and then back to the road, "I don't know, but I think I could probably get my way if I tried hard enough, though I may have a better idea on how to keep you tortured while out all day."
He chuckled again and began to rub a bit firmer now, getting off the high way a few exits later.