What do you think of this traffic control system?
All of the stoplights along a long street in the next town have been synched such that a person traveling at a level 35mph will encounter nothing but green lights as he drives. People going significantly faster or slower than the speed limit will come to a light before it turns green and will be made to wait.
There are signs posted along the route explaining as much.
Thus, I suppose, the driver is encouraged to stick to the speed limit without the city having to resort to the threat (and expense) of police action.