ST. PETERSBURG — The state's top transportation official said Wednesday that the Howard Frankland Bridge may one day become a toll bridge as the state seeks more money to improve roadways.With gas tax revenue on the decline, the state will use tolls to fill a void in financing road projects, said Florida Department of Transportation Secretary Ananth Prasad."Bridges last for a while — up to 80 years. But when you have to replace them, they suck up a lot of money," Prasad said in a meeting with the Tampa Bay Times editorial board. "If we're going to replace it, put a toll on it."The toll, he said, would subsidize the cost of reconstructing the bridge's northbound lanes, set to be replaced in 2022. The cost could top $500 million.This approach would complement the state's plan to eventually create toll express lanes along segments of interstates 275, 75 and 4, an option the Transportation Department will consider in coming months.Tolls, Prasad said, are the way of the future."People don't understand the real cost of funding infrastructure," he said. "Our gas tax is fixed per gallon, not a percentage of the price.''When the price of gas rises, people tend to drive less and the state gets proportionately less money. Fuel-efficient hybrid cars exacerbate the problem, he said.Department of Transportation District 7 Secretary Donald Skelton estimated the state has lost $1.6 billion in gas tax revenue over the last five years, impairing efforts to fix or build roads."We want all of these things," he said. "But we have to be able to pay for this."One option would be to eliminate free passage across Tampa Bay bridges, Prasad said. Another would be to impose a temporary toll on the Howard Frankland to pay for repairs.The department is also exploring mass transit alternatives, including express buses and light rail.Talk of tolls routinely raises questions about fairness and people's ability to pay. That was the case when express toll-only lanes were added three years ago to I-95 in Miami-Dade County.How would commuters react to a toll on the Howard Frankland?"There's a choice here," Prasad said. "We would maybe leave the other Tampa Bay bridges without a toll, so they could choose."Officials would not speculate about the amount of the toll or whether it would apply to traffic in both directions."This revenue will help to make the system altogether better," he said. "The concept is, you're paying for usage."Marissa Lang can be reached at [email protected] or (813) 226-3386.