The leaders of Maryland’s largest city and two largest counties on Wednesday urged the state Senate to act on legislation that would raise hundreds of millions of dollars a year for additional transportation projects.

“This is a big problem, and we need a big solution,” Montgomery County Executive Isiah Leggett (D) testified at a hearing of the Senate Budget and Taxation Committee. “My view is go big or go home.”

Leggett appeared on the same panel with Prince George’s County Executive Rushern L. Baker III (D) and Baltimore Mayor Stephanie Rawlings-Blake (D). All three praised a bill introduced by Senate President Thomas V. Mike Miller Jr. (D-Calvert) but said they remain open to alternative methods to raise more money for transportation.

Under current projections, state analysts say that within a few years Maryland will have only enough revenue for maintenance of its existing transportation network and not for new highway construction or planned rail projects, including the Purple Line.

Miller’s bill would impose a new 3 percent sales tax on gasoline, allow counties to collect another 5 cents on the state’s 23.5 cent-per-gallon gas tax and create regional authorities to raise additional funds for major rail projects.

“These are just possibilities, folks,” Miller told the committee. “These are proposals to jump-start a conversation. ... Our transportation trust fund is going to run dry.”

In recent weeks, Gov. Martin O’Malley (D) and his staff have been working behind the scenes in an attempt to craft a funding proposal that both Miller and House Speaker Michael E. Busch (D-Anne Arundel) will support and sell to their members.

Many lawmakers are wary of raising taxes, particularly at a time when gasoline prices are rising. House Republicans have argued that an increase in the gas tax is unnecessary.

Baker said at Wednesday’s Senate hearing that more state transportation revenue is needed to facilitate economic development in his county. He cited two projects in the works that will need transportation upgrades: a planned “destination resort” casino and a new regional hospital.

“We’ve got to have a solution,” Baker said. “We can’t continue to kick the can down the road.”

Miller also testified in favor of a second bill he has drafted that would create a “lock box” to ensure that transportation funds are being spent on transportation.

Under the bill, before diverting transportation funds elsewhere, the governor would have to declare a “fiscal emergency” and win support from three-fifths of lawmakers in both the House and the Senate.

“I don’t personally care for this proposal,” Miller told senators, adding that it may be necessary to reassure citizens.

House Republicans have argued Miller’s proposal does not go far enough.