Serious road cyclists do not often dally about when they're out for a ride, instead preferring to dance on the pedals at speeds of 20 mph and more. While they can easily do that on many National Park System roads, legislation pending in Congress could force them onto paved paths now enjoyed by walkers, folks with strollers, those in wheelchairs, and others not zooming along.

The legislation, whose main intent is to reauthorize federal highway funding and safety construction projects, dictates that "(T)he Secretary of the appropriate Federal land management agency shall prohibit the use of bicycles on each federally owned road that has a speed limit of 30 miles per hour or greater and an adjacent paved path for use by bicycles within 100 yards of the road."

In other words, according to Darren Flusche, a policy analyst with the League of American Bicyclists, cyclists who enjoy cruising roads in places such as Rock Creek Park in Washington, D.C, or Grand Teton National Park, could be forced off the roads in those parks and onto paved paths.

"If you write into federal transportation legislation that bicyclists are somehow unfit -- because again, the clause is called 'Bicycle Safety' -- it’s a really, really bad message to send that sharing the road with bicyclists above 35 mph is dangerous," said Mr. Flusche, who hasn't been able to determine who added the clause to the bill. "If you can write in a clause that says bicyclists have to use side paths if there’s one available, that kind of implies that maybe bicyclists shouldn’t be on the road at all. And so it’s really a dangerous precedent that we’re seeing."

Cycling is very popular in national parks, from Cape Cod National Seashore to Grand Teton National Park and on west to Mount Rainier National Park. At Cape Cod there's a great trail network that ties into bike paths in surrounding communities, and Grand Teton officials in recent years built a multi-use path to offer cyclists some protection from ponderous RVs and other vehicles.

At Yellowstone National Park, as in Grand Teton, there's a window early in the spring when the park roads are open to cyclists, but not to wheeled-vehicles, and many road bikers see a great challenge in riding the Going-to-the-Sun Road in Glacier National Park end-to-end.

While information on which parks have paved paths running parallel to their roads, and within 100 yards of those roads, is difficult to find, Rock Creek Park is one, says Mr. Flusche.

"It’s a major commuter route for drivers to get in and out of the city because it’s a park. It doesn’t have that many intersections where you have to stop, and so it’s a convenient commuter route for drivers. But it’s also a national park, so there’s also lots of recreational riders and transportation bicyclists," he said. "And there is a path, parallel to the road, for much of the length of it, and a lot of people would say that bicyclists should just be on the path.

"Beach Drive is the main road in Rock Creek Park, and many bicyclists use Beach Drive just to get their workouts and to get to and from work," continued Mr. Flusche. "Being forced on the path would really be killer for those bicyclists who are higher speed bicyclists. They’re almost going 30 mph themselves, and wouldn’t really be able to practically share that path with people taking a stroll or more recreational cyclists who are going slower pace. As it is, the path already tends to get overcrowded."

Another park that draws cyclists to its roads is Valley Forge National Historical Park, which has paved pathways.

“They are open to bikes now, but they’re shared paths with pedestrians, and women with babystrollers. They get pretty crowded on weekends. It works, because not all bicyclists use it, especially the guys who ride very fast," says Deirdre Gibson, the park's chief of planning and resource management. “It could cause a carrying capacity problem for us if road bikers were compelled to use parallel trails.”

National Park Service officials -- who the league maintains doesn't want bicyclists in the parks -- had no comment on the proposed legislation, saying they would comment if asked to testify on it. In the meantime, the League of American Bicyclists hopes to find a sympathetic senator who would work to remove the clause.

"We’re trying to target Montana, Idaho, and Wyoming, hoping we can build support in those states to have that clause removed. A lot of Western states have a lot of federal land," said Mr. Flusche. "Whether or not they have bike paths on them is a different question. Certainly, anywhere where you’re used to riding on federal land there’s a threat that at some point you might get pushed off if a trail develops."

The league has created a petition page on its website to fight the clause.