Popular game used in flirtatious situations. One person, Player 1, announces to Player 2: "my hand is an ambulance, say red light when you want me to stop." Player 1 runs his/her hand slowly up Player 2's leg, starting at the knee and aiming toward the crotch. When Player 2 feels too uncomfortable for any further progress, he/she announces "stop!" Player 1 replies "ambulances don't stop at red lights" and proceeds with moving his/her hand toward Player 2's crotch.
Girl: "Hey, do you want to play ambulance?"
Boy: "Um, ok, though I'm not really sure how to play...."
Girl: "It goes like this: My hand is an ambulance, say red light when you want me to stop"
(Hand proceeds slowly up boy's leg)
Boy: (Noticeably uncomfortable) Red light! Red light!
Girl: Ambulances don't stop at red lights! (Hand proceeds up his leg)