A California transportation agency recently proposed what could become the most unpopular tax of all time: A tax for simply driving your car.

The Metropolitan Transportation Commission of San Francisco is behind the idea and has said that the tax would work by installing GPS units into cars to track the miles that they travel. The vehicle owners would then be charged accordingly, with low-income drivers exempted.

The hope is that a VMT (vehicle miles traveled) tax would cut down on pollution and traffic congestion, while raising funds for things like road construction and surface repair.

Randy Rentschler, spokesman for the MTC, said that the group knew the proposal could be a longshot and could take a long time to implement. Theoretically, it could take up to a decade before the plan would be rolled out in full force.

"I don't want to say it's pie in the sky. A VMT charge is really an option for the future to be looked at and considered," he said.

Given the very low popularity gas taxes have been met with in the past, the proposed driving tax seems like a very bold move. Consumers hate frequently being reminded of taxes when they gas up, but this VMT charge would take that to a whole new level.

The Association of Bay Area Governments is slated to analyze a study of the proposal on Thursday.

California residents are sure to watch this one closely.