NATION - For more than half a century, highway advocates have been the loudest voices on transportation policy, but that may change this year as lawmakers push to include more funding for public transit in the next authorization bill.

The federal Highway Trust Fund now apportions about 81 percent toward roads and bridges and 19 percent to mass transit. Some lawmakers and transit advocates are mounting a significant campaign to level the funding distribution, which has highway supporters warning that such a funding shift could upset sensitive plans -- including a possible increase in the federal tax on motor fuels -- to boost trust fund receipts.

"If the bill starts looking more negative on highways, then users that have been supportive of fuel tax increases would turn their back on it," said Greg Cohen, chief executive of the American Highway Users Alliance. "There is potential that the whole bill could be slowed down here."

Highway groups are especially concerned about a bill (S 1036) introduced by Senate Commerce, Science and Transportation Committee Chairman John D. Rockefeller, IV, D-W.Va., to make increased transit use a priority in the authorization.

Rockefeller's bill, cosponsored by rail advocate Frank R. Lautenberg, D-N.J., would set policy goals to take more cars and trucks off the roads and move more people from highways to riding trains. The argument is that an investment in mass transit, including rail, gives people more choices and eases congestion on the nation's highways.

"People want options," said James Corless, president of Transportation for America, a coalition of groups involved in housing, environment, public health and other issues. "I'm a highway user, and I want trains. I may not use it, but someone else will . . . We need to work together. We have a fight between highways and transit and we have to get over that."