I have deliberately overtaken trucks with my wife in the passenger seat with her skirt hitched up to give the drivers a good look at her thighs. Once I was fingering her as I passed a truck. The fact that he could see my hand between her legs really turned her on and she had a shuddering orgasm.
There have been evenings when I have loosened her clothing and played with her as I drive - skirt up, knickers off, blouse open, no bra. Normally she'd cover up if I car came the other way, but one night I persuaded her to leave her shirt open as we passed cars. I don't know if anyone saw her, but her breasts looked good lit up by car headlights!
On occasions my wife has also sucked my cock whilst I've been driving at night. Once I was driving a van and a guy passenger in a passing car saw her head in my lap. I like the idea of her being stranded 50 miles from home and begging a guy for a lift and him only being willing to help her if she sucked his cock. Would she do it or walk home? She says she'd walk, but I'd rather she "paid" for her ride.
Peter C