If everyone could be persuaded to buy a Prius or Volt or take a bus to work, the cost of building roads and bridges and keeping them plowed would remain pretty much constant. Government would still need nearly the same revenue flow to maintain it's transportation system. A once a year stop at the DMV to record mileage, or how about the nearest police or fire station, seems like a fair way of raising taxes to build an maintain roads.

Some states charge huge registration fees while others have high gas taxes. This would just be a third method of paying for roads. Since electric cars need roads and bridges as well as plowing, it is only fair that they be taxed too.