MOUNT DESERT ISLAND — For the past four summers, campers on the east side of the island have shelled out $2 each time they boarded a shuttle bus that took them into Bar Harbor or Acadia National Park.

Ridership was solid, and each summer a good number of hikers and tourists left their cars at their campgrounds. But while the buses were used, say transportation officials, they weren’t filled.

Not so this summer. Thanks to a decision to drop the fare, ridership on the route, which links seven campgrounds, surged 600 percent, according to Downeast Transportation, the nonprofit bus company that ran the service. General Manager Ed DeWitt said recently the shuttle route was so popular the only complaints he heard were from people asking for the buses to run more often.

“The comments [from riders] were outstanding. People were saying, `Why would anyone drive a large RV around when you’ve got a free bus?”‘ said DeWitt.

More than 12,500 people used the shuttle this year, which ran from late June to Sept. 1. The bus route for Downeast’s green-and-white buses began at the Narrows Too campground in Tremont and included stops at Bar Harbor and Sand Beach in Acadia National Park.

The results were so successful that advocates for an islandwide public transportation system are pointing to it as an example of the public’s willingness to use public transportation.

“There was a question as to how the bus system was going to work,” said Ken Olson. Olson is president of Friends of Acadia, an advocacy group, which along with area campgrounds and the park, contributed funding to help make this year’s shuttle free for riders.

“I think most people want to do the environmentally sensitive thing,” said Olson, “but there is a difference between what our attitudes are and what our behavior is.” In the past, Olson believes, just a few dollars made the difference between visitors climbing into their cars, and climbing aboard the shuttle bus.

Friends of Acadia, the national park and the four island towns are supporting a proposal by the MDI League of Towns to establish an islandwide transportation system, slated to be running by summer 1999. The League of Towns is a coalition of representatives from towns in the MDI area and Acadia. According to Len Bobinchock, assistant superintendent at Acadia, the group has already received a commitment from the state for a $500,000 grant for the system.

Receipt of the grant is contingent upon Congress appropriating the funds this fall, said Bobinchock. In addition, he said, at least $100,000, or 20 percent of the grant, must be raised from the local area. To date, each of the island towns have voted to support the system, and Friends of Acadia has pledged a $30,000 contribution. Donations from private businesses are still being sought.

Although details for the islandwide system, such as whether the new transportation system will be free of charge and where it will run, are still being hammered out, the group is likely to begin to purchase buses beginning early next year.

The group will be briefed on the results of this summer’s shuttle run at their next meeting in October. Of the 600 percent boost in shuttle riders, Bobinchock said, “We are obviously very pleased.”