Agreed on headlights in the rain/snow/fog. Heck, just turning lights on at NIGHT seems to be difficult for some folks, they drive along with no lights at all at night and can't take a hint from people flashing their lights.
Pretty sure I read somewhere that you're not supposed to enter an intersection if you can't make it through. Not nice to block the cross traffic if the cross traffic gets the green light and you're still stuck in the intersection.
Following along at a reasonable distance in the right lane, and somebody behind just has to get to that exit ramp a fraction of a second faster, so they pass me, squeeze in front, slow down, make me slow down, just so they can take the exit. Really, was that necessary?
Four-way stops are starting to drive me up the wall. That's gracious of you that you're waving at me to go first, but geez, YOU STOPPED, THEN I STOPPED, IT'S YOUR TURN, I'M WAITING FOR YOU. On the flipside, there are those that just slow down knowing that I'm about to stop, but they don't want to stop so they just keep rolling through. Then there those who think that since there are 3 or more cars stopping, and #2 is waiting for #1 to clear, then #3 is free to go before #2. Oh yeah, and there are the ones who seem to think that since they came to a complete stop behind the car in front of them, then they are free to go when the car in front starts moving. See that a lot when only a handful of people remember to treat malfunctioning traffic signals as four-way stops during a power failure.
