You can combat boredom in slow-moving traffic by engaging in all sorts of activities: listening to music, checking out your reflection, flirting with neighboring drivers. If you are driving and notice a cute person next to you, get their attention by subtly flirting.
Look over quickly. Try not to stare at the other driver, just give him a quick once over at first. If you suddenly start staring at him intensely, you'll come across as strange or desperate.
Do a double take. Let her know that you're interested by checking her out a second time. At this point, try to make eye contact. If she doesn't notice you, you may want to give up and rock out to a song on the radio instead.
Give him a sign that you're flirting after you lock eyes. Smile, wave or offer some other gesture to let him know that you're interested.
Wait for a response. If she seems into it, then continue flirting. Otherwise, just look away and pretend to fiddle with the radio.
Leave him with a quick wave or mouth something to him. See what he does in turn before driving away.
