So Congress hasn’t resolved the 2011 budget impasse yet, and already there are bigger budget battles about to consume Capitol Hill.

With the release of the Republican budget proposal for fiscal year 2012 due out tomorrow, we can expect proposals to drastically alter Medicare to overshadow every other program on the chopping block. But House Budget Committee Chair Paul Ryan has promised at least $4 trillion in cuts over the next decade, so transportation funding must be on the table. Despite several hearings on transportation on the Hill these past weeks, however, it seems increasingly difficult to find the issue of transportation in major media coverage of the budget debates.

Why is it so hard to have an “adult conversation” on transportation?

It’s easy to say that the efficient movement of people and goods is critical to American competitiveness, or that our infrastructure is falling apart, but look for these issues within the broader dialogue on the budget and you won’t find them. The problem of transportation funding is not ‘sexy,’ nor is it resolvable without measures that have become politically out of fashion: new or expanded revenue streams.

Transportation is linked to many policy priorities that government aims to address, including public health and job creation, but “many people, including media, do not fully appreciate what the federal role is with regard to transportation,” says Sarah Kline, Policy Director of Reconnecting America. “When someone is driving down the street and hits a pothole, they don’t think, ‘Let me call my member of Congress to complain.’ They think, ‘I’m going to call the mayor.’”

Of course, your local taxes do not cover the costs of maintaining all of your roads, sidewalks, transit lines, and highways, and City Hall depends on Washington to keep you moving. That’s why America’s mayors come together in D.C. every year and why transportation improvements are consistently at the top of their funding wishlist.

But when voters list their top concerns, transportation is not what they think of. “I think jobs, spending and the economy are at the forefront of people concern’s today,” says Alex Goldschmidt of Smart Growth America, “and transportation just hasn’t been linked closely enough with those issues in the past. That’s too bad because creating transportation options addresses all those concerns.”

Currently, the Highway Trust Fund receives money from gas taxes (that have not been raised in almost twenty years) to fund a variety of transportation infrastructure and operations costs across the country. There have been well-documented accounts of wasteful spending (see: Bridge to Nowhere) but reforming the system alone would not save enough money to . Even if we were to stop expanding highways or building new ones, maintaining what we already have would be impossible given current revenues.

According to the Congressional Budget Office, the Highway Trust Fund brought in $35 billion in fiscal year 2010, but the Federal Highway Administration estimates that just addressing the problems of existing bridges in disrepair would cost almost $80 billion today.

Simply put, suggests Deron Lovaas of the NRDC, transportation is an unpopular topic in the budget debate because it means talking about raising taxes. “There’s a lot of evidence and conviction – including from unlikely allies such as the Chamber and the AFL-CIO – that transportation is revenue-starved. Fixing that may require raising fuel taxes and/or cutting oil company subsidies, which are dirty words to some. An adult conversation is overdue, one about cutting waste AND boosting revenue.”

What the country needs is a larger transportation funding program, not a smaller one. Yet the GOP seems unwilling to even consider measures that are ideologically consistent with conservatism — like reducing subsidies. On Fox News Sunday, Rep. Ryan was pressed to address how a budget could be balanced with no new revenue streams. Would $40 billion in cuts mean curbing our existing tax breaks for oil and gas? Ryan hemmed and hawed, giving no indication that he’s reversed his earlier stance — that the subsidies should remain.

So who will step forward and get serious about how we’re going to pay for transporation? Public opinion polls consistently show that Americans support more — and smarter — infrastructure investment. Voters aren’t so enthusiastic when it comes to paying for that investment, but maybe they are ready to have an adult conversation about it.