Public transportation in the United States has faced a perverse situation these past few years. Thanks to high gas prices, more and more Americans are riding buses and trains. But thanks to budget crunches, transit agencies are actually cutting services at the exact same moment.

Over at Transport Politic, Yonah Freemark has a post highlighting one particularly dramatic example of this in Pittsburgh. Due to a $64 million funding shortfall, the city’s Port Authority is threatening to close roughly 40 percent of its routes in the city this year. The before and after maps are really stunning. Here’s what Pittsburgh’s system looks like before the cuts:

And here’s the skeletal “after” shot:

It’s not as if Pittsburgh’s population is shrinking and can get by with a smaller transit system, either — according to the Census Bureau, Allegheny County appears to have grown in the past year, and the city is expected to keep adding people in the coming years. Freemark also notes that Pittsburgh is a particularly transit-dependent city: Nearly 20 percent of its workers use transit to get to work, a high number even for a city, and more than 25 percent of the city’s households have no vehicle.

Although Pittsburgh is an extreme case, it’s not an isolated one. Transportation 4 America has been trying to track service cutbacks around the country with this useful map. The Massachusetts Bay Transportation Authority in Boston recently carried out a series of service cuts because of a $161 million funding shortfall — even though overall ridership rose roughly 3 percent last year. States and cities don’t have the money to keep up with growing ridership.

There’s a federal policy question here too: Right now, as the House and Senate are hashing out a transportation bill, one question at stake is whether Congress should do more to help states and cities keep their buses and trains running when local budgets get squeezed.

At the moment, Congress doesn’t do this. Federal funds for mass transit can only be used for new capital projects, not operations. That explains why Pittsburgh is getting $348 million from Congress to build a light-rail tunnel extension under the Allegheny River, but can’t find $64 million to keep its existing buses and trains running.

Now, one could argue that local governments should be responsible for keeping Pittsburgh’s buses running. After all, there’s nothing stopping Pennsylvania from doing what other states have done and raise revenues — say, fuel taxes — in order to fund Pittsburgh’s transit service. (The Port Authority of Allegheny County is also using the specter of service cuts to demand a restructuring of the bargaining agreement with transit employees, so there are still plenty of ways this fight could resolve itself without federal aid.)

But even stepping back from Pittsburgh’s situation, critics of the current transit-funding approach argue that it has potentially harmful side effects for the nation as a whole. Freemark, for instance, had earlier done a short study finding that a heavy reliance on local funds for transit operations seems to have created inequalities around the country. Poorer cities, not surprisingly, tend to have much shabbier transit service than wealthier cities. Freemark argues that this, in turn, forces more low-income households to purchase cars, raising their costs and putting these areas at a further disadvantage.

It’s possible, however, that this could change. The transportation bill that the Senate passed in March would have provided states more flexibility to use federal transit funds to operate existing buses and trains in addition to buying new equipment. This idea was never adopted by House Republicans, though, so it’s still unclear whether it will make it through. The two sides are currently negotiating over a larger bill this week.