WASHINGTON The Congressional commission created to recommend ways to fund road construction during the next two decades wants to replace the federal fuel tax with a mileage-based tax.

But members of a U.S. Senate committee say the proposal raises serious issues of privacy.

Members of the National Surface Transportation Policy and Revenue Study Commission discussed the concept late last month during a hearing before the Senate Environment and Public Works Committee.

Taxes collected on vehicle miles traveled, which is known as VMT, would require satellite-based technology to read how many miles a vehicle travels in a given state.

Jack Schenendorf, vice chairman of the transportation commission, told the Senate committee the government should replace the federal fuel tax with a mileage-based tax by 2025. By then, he said, more people will be moving toward hybrid vehicles and alternative fuels and fuel tax revenues will plummet.

To get to the eventual implementation of a VMT tax, commissioners are recommending an increase in federal fuel taxes of 25 cents to 40 cents per gallon from 2010 through 2015, along with other ways of raising revenue including tolls, congestion pricing and public-private partnerships for new construction.

Schenendorf said he understands that some people might question the issue of privacy during the move to a VMT-tax system. Several senators weighed in on that topic.

"Don't waste a lot of time on that one because that ain't gonna happen," said Sen. James Inhofe, R-Okla., the committees ranking Republican.

Schenendorf replied that the government would have until 2025 under the recommendation to improve the technology.

Senate Committee Chairwoman Barbara Boxer, D-Calif., suggested that instead of having technology installed in every vehicle to track where it has been, a system could be devised for reporting mileage when owners renew their vehicle registrations.

"There are other ways to figure out how many vehicle miles youre using other than having some Big Brother system tracking your every move," Boxer said.

The commission's main objective is to have the federal government invest $225 billion per year for 50 years to fund and maintain transportation systems.

Before a VMT system could be put into place, the commission recommended that several methods of increasing revenue be explored.

Those include increased use of tolling; congestion pricing and private financing; and increased state and local revenues.

Commission Chairwoman Mary Peters, the current U.S. transportation secretary, was absent from the Senate hearing. She and two other commissioners disagree with the majority opinion on the commission that a temporary fuel tax increase and an eventual shift to a VMT is the best way to fund transportation.

Peters is a strong proponent of tolling and public-private partnerships. She wrote her own rebuttal to the full commission report to separate herself from the commission's recommendations.

The commission's recommendations are far from becoming government policy. Legislation would have to survive the House, Senate and the White House during the next re-authorization of the federal highway bill in 2009.