This editorial from the Idaho Statesman says that a proposal to switch from a per-gallon gas tax to a per-mile taxing system is flawed.
"Some 450 Treasure Valley commuters will hit the streets next year, computers and satellite equipment in tow. The gadgetry will measure how many miles the drivers log over two years, and spit out sample monthly bills comparing their monthly per-gallon gas tax with fees based on miles traveled."
"In a sense, the results of the University of Iowa study are irrelevant. The mere fact that the study is in the works points out that a per-gallon gasoline tax is a business model as outmoded as the tailfin. It belongs to a time when all cars ran on gas, lots of it, and motorists tanked up without giving it much thought."
"A tax per gallon may be a dated dinosaur, but a fee per mile presents its own set of problems."
"Idaho faces a serious need to convert money into asphalt - a shortfall of $200 million a year. The state probably should start by looking at increasing vehicle registration fees, which now range from $24 to $48 and rank 30th in the nation. The state should also look at the viability of toll roads, as an alternative to crowded routes such as the Treasure Valley's Interstate 84. Falling back on the gas tax is a bad idea because, structural flaws aside, the state's gasoline tax is already high enough. Only 10 states top Idaho's 25-cent-per-gallon tax."