"It's not just getting people out of the car, it's enhancing the experience," Rogoff insists, and says some transit systems allow users to bring along their bikes. He rebuffs my assertion that getting Americans out of their cars, in any meaningful numbers, is a tall order.

Every time gas prices have risen in recent history, he says, transit ridership increases. When gas prices fall again, so does transit ridership, but—and this is key—it doesn't fall back to pre-gas-spike levels. Of course, he's referring to commuters, not park visitors on vacation. Nonetheless, he says two important demographic shifts bode well for transit ridership on federal lands. For one, as baby boomers age, they'll be less interested in driving and more interested in enjoying the view from a shuttle or train. Secondly, he points to declining numbers of young adults getting their driver's license at 16 and says this generation is more transit-friendly.

"We're not naïve, we know there are a lot of Americans who are attached to their cars, and for a lot of National Forests and National Parks, if you're traveling there from a distance, the car is the only way to get there. But once they get there, providing them a choice is a real opportunity," Rogoff says.

Unfortunately, it's an opportunity that exists at the whim of legislators, and funding for Transit in Parks was snuffed in the latest version of the transportation bill (MAP-21), which President Obama signed last summer. That means once these current projects are complete, there will not be an ongoing funding vehicle for more projects focused specifically on reducing vehicular traffic and providing new transportation options on federal lands (although other funding avenues exist through federal lands programs).

There is the chance that the program will be resurrected—in some form—in future transportation bills. Successful projects such as those seen in Maine's Acadia National Park will surely serve as case studies by lobbyists who want to see more federal lands transit options. With 2.2 million visitors, Acadia is one of the most popular parks, but congestion was a major issue before the launch of a bus system, on which ridership has grown from 142,000 per year in 1999 to 400,000 in 2012—with an average of 5,000 riders per day.

But the federal government isn't the only ray of hope. In Yellowstone, municipal transit providers from Idaho, Montana, and Wyoming have collaborated on a bus system that not only serves visitors to the national park, but also connects them with nearby towns, including Idaho Falls and Cody.