> It makes sense because gas usage is very correlated with road wear, so people who drive heavier vehicles pay a proportionate share of the road maintenance costs.

There are also some cases where it makes no sense, particularly since fuel tax is a primary source of funding for infrastructure and repair.

A Toyota Prius and a Ford Focus are both around 3,000 lbs, will do roughly the same damage on the road. The Prius gets 58 mpg city and 53 highway. The Focus is at 30 city 40 highway. So for city driving the Prius driver contributes 1/2 as much to the fuel tax revenues.

It's a nice incentive to reduce emissions, however the Prius driver is not contributing proportionally to the fuel tax.

If only we could charge make a charge based on weight, mpg, and miles driven.

The brouhaha over a Prius (or heck, my Focus Electric) not paying fair share of gas taxes is overblown since hybrids and electrics still constitute a minuscule % of total road wear.

The issue will come to a head when we have 4x4s and 18 wheelers en masse hybridized or fully electric in large quantities. I don't see that happening for a decade or more out.

I honestly don't ever see the typical 4x4 being a hybrid. Living in rural Arkansas, almost everyone I know who drives a 4x4 drives an older model, and working on them is a large part of the experience.

I drive a 2000 Jeep, and wouldn't even consider buying a hybrid or fully-electric version. A diesel, absolutely, but not anything with a battery pack.