I find it incredibly annoying when people drive a few miles per hour under the speed limit on certain sections of road where I know if I drive a certain speed I'll hit all the green lights. For example... on my way home from work I get off the highway to get on Michigan Ave. and I know when I leave that stoplight, if I drive 60 mph (in a 55 zone) the next light I come to will change to green by the time I get there... and if I continue at 60, the next light will also be green, whereas if I drive 50 or 55, that light will have turned red. If I continue through that light, I know if I drive 62 or 63 for the next 7 or 8 miles I'll hit the next two stoplights while they're green also. Then as I turn onto a city street (45 mph zone) I know if I accelerate briskly and drive about 47 or 48 mph I'll make every stop light on a 4-5 mile stretch of road before I make a right turn onto another city road where if I drive 40 mph, I'll pass the last stoplight before I get home while it's green.