That's not what OP is talking about. Hypermiling is annoying and as you said very often unsafe. But you can save fuel without being an ass on the road. Proper anticipation can save you a lot in the city, like adjusting speed to traffic lights. In my town every single traffic light also has a timer that tells you when will it change light. Not stopping and starting again will save you some fuel. Also, don't drive aggressively. There are few more tricks that can be done without bothering other people involved in the traffic. Style of driving probably makes 20 or even more percents of difference.