Since the advent of the hybrid at the turn of this century, an increasingly large group of hardcore fanatics have taken up hypermiling. For the uninitiated, hypermiling is the practice of using modified driving techniques to get the maximum possible fuel efficiency. There are hypermilers who claim to get over 100mpg from their Priuses and Insights. The problem is that techniques like pulse and glide involve significant fluctuations in speed. By accelerating quickly and then coasting for long periods using regenerative braking to recharge the battery as much as possible and then repeating ad nauseum, they minimize the load on the engine. This is fine when a vehicle is driving in little or no traffic. Unfortunately, when there are other cars around, an extreme hypermiler can pose a real impediment. Differences in speed are often a source of accidents and people who aren't driving hybrids won't want to be stuck behind someone coasting along. There is nothing wrong with trying to maximize fuel efficiency and everyone should be trying to drive efficiently. However, even hypermilers need to be cognizant of other drivers around them and avoid being obstructive.