ANDERSON — The state Transportation Department says a $15 per-axle fee on cars and trucks would help erase a $2 billion annual backlog in secondary road building and maintenance.

The state Highway Commission endorsed the fees this week. Passenger car owners would pay $30 more each year, and heavy trucks would pay $90 more.

Rick Todd, president of the South Carolina Trucking Association, said his organization likely would oppose the fee.

Gov. Mark Sanford and top legislators are cautious about the proposal, which would require their approval.

Two years ago, the Transportation Department won support for a gas tax increase from the Business Alliance for Transportation, representing the state’s trucking industry.

The switch in strategy toward a user fee appears to be an acknowledgment that high gas prices make support for a gas tax increase more challenging, said state Anderson Republican Rep. Ronny Townsend, chairman of the House committee on public works and education.