After decades of rejecting tolls on highways built with federal money, Congress is edging toward a decision to give states broad authority to levy tolls as a way to relieve traffic congestion and raise funds for road building and transportation.

The proposal, contained in the Senate version of a six-year transportation bill being negotiated with the House, has set off a fierce behind-the-scenes lobbying battle involving a host of powerful groups.

Opposing the Senate language are the AAA, the American Trucking Associations, the American Farm Bureau and the American Highway Users Alliance. Supporting the changes are coalitions representing state highway departments, road building groups, the U.S. Conference of Mayors, leading environmental organizations such as Environmental Defense and the Reason Foundation, which advocates free-market solutions to economic and social problems.

"This would basically remove the limits that have been in place for many years and could represent a sea change in how we go about financing improved transportation in states across America," said Michael Replogle, transportation director for Environmental Defense.

The debate over tolls has raged since colonial times. Before the interstate highway system, tolls financed limited-access roads such as the Pennsylvania and New Jersey turnpikes.

Since the passage of the Federal-Aid Highway Act in 1956, travel on the interstate system has been largely free. But several factors are combining to cause Congress to reconsider this policy.

New systems using electronic sensors can levy fees on vehicles without toll booths. The technological advances created intriguing possibilities for alleviating heavy traffic by giving motorists the option of paying to enter fast-moving, congestion-free lanes similar to high-occupancy vehicle (HOV) lanes.

Some jurisdictions, such as San Diego, are experimenting with the use of fast lanes at rates that change every few minutes, depending on traffic. Maryland is considering a proposal to create similar toll lanes on congested roads such as the Capital Beltway and Interstate 270.

But an even bigger factor for lawmakers is the possibility that tolls could raise billions of dollars over the next six years for transportation.

Revenue for transportation programs is now derived mainly from the federal gasoline tax, which neither Congress nor the White House wants to increase in an election year.

The White House has set a $256 billion ceiling for the six-year transportation bill, well below the $318 billion proposed by the Senate and the $284 billion called for by the House. White House officials say they will urge President Bush to veto the bill if it exceeds his ceiling.

But the administration has indicated that it favors the tolling proposals in the Senate bill, signaling a possible way out of the funding impasse.

"We're in favor of giving states a menu of options, including tolling, to manage traffic flow," said Brian Turmail, a Transportation Department spokesman.

The Senate bill allows states or transportation authorities "to toll any highway, bridge or tunnel, including facilities on the interstate system, to manage high levels of congestion or reduce emissions," after informing the secretary of transportation.

House language, championed by Rep. Mark Kennedy (R-Minn.), is far more restrictive. HOV lanes, which are widely viewed as underutilized, could be converted to toll lanes. Otherwise, tolls could be imposed only on new lanes or roads, and the tolls would cease when the highway bonds were paid.

The House approach has the backing of several powerful groups, which warned in a letter to House-Senate negotiators that placing tolls on existing interstate highways could "force many motorists onto local roads, which are at least four times as dangerous as interstates."

A spokesman for the American Trucking Associations said the organization worked with Kennedy on the proposal's language.

"We're opposed to tolls on existing highways," said Darrin Roth, director of highway operations for the organization.

"What we don't like is taking existing lanes and turning them into toll roads," said Gregory Cohen, president of the American Highway Users Alliance. "These have been paid for with gas taxes, and you're never going to get the support of the public if you start taking things away."

But the Tolling Coalition, made up of state officials, road builders and others, has argued with lawmakers that the Kennedy plan would prohibit the most innovative approaches.

"The need for highways far outstrips the available resources generated from traditional funding methods," it said.

A Senate bill would allow states to toll any highway, bridge or tunnel "to manage high levels of congestion."