Public transit advocates were blindsided when House Republicans introduced a five-year highway bill two years ago that proposed eliminating the Highway Trust Fund’s transit account.

The proposal would have ended the guaranteed cut of federal motor fuel tax dollars that has been set aside for urban rail and bus systems since the Reagan administration.

“We got caught flat footed,” said Leanne P. Redden, the acting executive director of Chicago’s Regional Transportation Authority.

Ultimately, the House bill was never brought to the floor — in part because Republicans from transit-dependent suburban districts rebelled — and the two-year surface transportation package that emerged from conference negotiations retained the formula funding for public transit.

But the experience taught transit advocates not to take their federal funding for granted — and this year they are working to line up bipartisan support ahead of an effort to write a new surface transportation authorization.

Redden and other transit advocates have put together the Getting America to Work coalition to lobby for increased transit funding as more Americans crowd into urban areas. And last year, Reps. Daniel Lipinski, D-Ill., and Michael G. Grimm, R-N.Y., founded the Congressional Public Transportation Caucus to build support among lawmakers for transit funding.

The men represent two of the most transit-dependent districts in the nation. Lipinski’s constituents in the western suburbs of Chicago rely on the commuter rail. And Grimm’s district encompasses all of Staten Island and parts of southern Brooklyn.

Getting other Republicans on board hasn’t been easy for Grimm. Many of his fellow party members represent exurban and rural districts where cars are king. To make matters harder, the past two elections brought an influx of GOP tea party sympathizers wary of big federal investments.

“It’s not in their face like it is everyday for me,” Grimm said.

But the caucus is making progress. Redden said her coalition was buoyed when Rep. Tom Cole joined the caucus because the Oklahoma Republican brings the endorsement of a GOP conservative who doesn’t represent part of a megalopolis. Transit supporters hope more Republicans will follow.

The efforts by transit supporters already seem to be paying off. As the House Transportation and Infrastructure Committee begins work on a new surface transportation bill, there has been no talk of splitting transit away from the Highway Trust Fund.

And a tax extenders measure that the Senate Finance Committee approved last week would increase through 2015 the pre-tax money that employees can set aside to pay transit fares. The provision — which would set the pre-tax benefit for rail and bus commuters at the same level as pre-tax parking benefits — would apply retroactively to January.

As the next highway bill is drafted in the coming weeks, the coalition and caucus will make the case that transit is an integral part of a broader national transportation network that benefits everybody.

“There’s an absolute connection to benefits for motorists,” Jack Basso, the former finance guru for the American Association of State Highway and Transportation Officials and now a transportation finance consultant at Parsons Brinckerhoff, said last week at a panel discussion sponsored by the congressional caucus.

Basso said transit systems reduce road congestion and make driving time more predictable for motorists. The challenge facing transit advocates, he said, is to show the millions of drivers paying the federal gas tax every time the fill up how they benefit from rail and bus system investments.

Of immediate concern to transit advocates is the projected shortfall in the Highway Trust Fund, which is expected to run short of the money to meet its obligations sometime this summer. Nobody expects Congress to raise the gas tax in an election year to fill the gap, which is likely to leave transportation authorizers begging appropriators for a short-term transfer of general funds.

Grimm said that worries him, because “it’s often a fire drill” and legislation created under such circumstances “is never as good as it should have been.”

In the long run, federal investments in mass transit — like spending on roads and bridges — is likely to require a fundamental restructuring of the Highway Trust Fund.

“Just raising the gas tax will not get us out of the woods for the long-term,” Basso said. “We’re never really getting at the cancer that plagues us.”