What agitates drivers the most in S'pore?

[True Believer]

What upsets drivers the most on the road? Is it when you signal to switch lanes, and the vehicle behind in that lane immediately speeds up to prevent you from doing so? How about after you allow the driver behind you to switch into your lane, but he does not even bother to wave to show his gratitude? Drivers who switch lanes suddenly and only turn on the indicator when they have crossed 1/2 way into your lane?