As more people try to squeeze more cars inside national park boundaries, some of the most popular parks are planning new or expanded shuttle systems similar to the successful one at Zion. Among park advocates, all eyes are on the huge transportation bill currently moving through Congress; many of these plans will live or die based on what the appropriators decide. Here are a few of the things you may encounter now and on future national park vacations:

Grand Canyon

WHAT IT HAS NOW: Between March and November, certain roads along the South Rim are closed to private vehicles. You can still drive to the developed areas at Grand Canyon Village, but you must take one of the free shuttle lines out to view spots along the roads to Hermits Rest, Yaki Point and Mather Point.

WHAT IT PLANS: A longstanding plan for a light rail system to bring people in from the gateway town of Tusayan, Ariz., to the South Rim got so far that some of the train stations have already been built. But sticker shock may have derailed that idea permanently, and now Congress is strongly encouraging planners to look instead at a shuttle bus system along the same route.

Great Smoky Mountains

WHAT IT HAS NOW: There is free trolley service between Gatlinburg, Tenn., and the park entrance, with limited stops within park boundaries.

WHAT IT PLANS: Peak season traffic is legendary at this Tennessee park, especially in the Cades Cove area of historic Appalachian structures. There is an 11-mile, one-way loop that, like the Zion of old, can barely accommodate its 2 million driving visitors a year. In the fall leaf season, it can take up to five hours to creep through. The Park Service plans a free mandatory shuttle, prohibiting private cars entirely at the busiest times. Local opposition is stiff, but Zion's success may be winning converts. Herb Handly,executive vice president of the Smoky Mountain Convention & Visitors Bureau, was a shuttle skeptic before he visited Zion. "I went from looking at it negatively to coming back and saying I wish we had a system like that in our community and in our national park," he said in a phone interview.


WHAT IT HAS NOW: Maine's Acadia is one of the friendliest parks to car-less travelers. With a network of eight bus routes connecting Bar Harbor with the park attractions on Mount Desert Island -- including a stop at the airport -- it's possible to fly in for an Acadia visit with no stop at the Hertz counter. The Island Explorer shuttle system, which runs as often as every 15 minutes on some routes between June and October, is free and voluntary (you can still drive in and do battle for limited parking within the park).

WHAT IT PLANS: To expand some routes and meet growing demand (312,000 people rode the system last year), Acadia plans to add eight or 10 buses to the 17 it now runs. In the long term, the park service plans to build a new visitors center on the mainland where day users can park and board the shuttle.


WHAT IT HAS NOW: The park operates a limited voluntary, free shuttle system in the heavily developed eastern third of Yosemite Valley, and just took delivery of a fleet of low-emission diesel-hybrid vehicles to replace its fleet of older city buses. A regionwide system, YARTS, provides alternative transportation between the park and local towns for a per-passenger fee.

WHAT IT PLANS: The park's current master plan envisions a set of three satellite parking areas on the western edge of the park, with Zionlike shuttle transport into Yosemite Valley. But stiff opposition from the surrounding communities may scuttle that project.

Grand Teton

WHAT IT HAS NOW: There's no public transportation system operating at the park.

WHAT IT PLANS: The Park Service is proposing a scheduled shuttle system between the town of Jackson, Wyo., and park headquarters and into major activity centers, including Jenny Lake, Colter Bay, Jackson Lake Lodge and Signal Mountain. Jackson not only supports the plan but has offered municipal space for shuttle facilities. The park's master plan also proposes a network of bicycle and walking paths along major roadways.

-- Steve Hendrix

In California, Yosemite National Park officials hope to expand parking and offer shuttles into Yosemite Valley.