“A mileage tax isn’t fair. Lighter fuel efficient vehicles do less damage to the roads than oversized gas guzzlers do.”
Who said the tax would apply equally for all types of vehicles? For that matter, who said that the tax cannot be adapted to also include when you drive and where you drive? And, after that, why not adjust the tax to income levels, so that the rich pay their fair share?
Generally speaking, the gas tax does a very good job of this without needing to be adjusted.
Big vehicles, which damage roads more, tend to use more gas. A person owning a big vehicle pays more in taxes.
The rich tend to buy vehicles that are more luxurious and are usually less efficient. They pay more taxes.
If you drive a lot, you will buy a lot of gas and will pay more taxes.
All these concerns are built in the gas tax already.