Passengers board the Island Explorer next to the Village Green in this June 30, 2014, file photo.

Mount Desert Island’s fare-free bus service is on track to finish the tourist season with a 10-percent increase from its 581,305 riders of 2017.

As of Aug. 31, Island Explorer has carried 497,740 passengers around the island, including cruise ship tourists visiting Acadia National Park. That’s about 10 percent above the number carried as of that date last year, and the pace is unlikely to taper off much before the season ends on Columbus Day, said Paul Murphy, the service’s executive director.

[See all Hancock County coverage here]

Island Explorer’s passenger count is — like the estimated number of visitors to Acadia — one of the region’s basic economic indicators. It also comes at a time when Bar Harbor and Acadia are working on several plans to reduce traffic congestion.

“I think visitation is up in the park and more people are coming. More people are learning that it is not easy to park and get around Acadia when it is busy, so they take the bus,” Murphy said Tuesday.

[Bar Harbor bus service seeing increase in tourist riders]

Final estimates won’t be available for at least two weeks. While Bar Harbor is a year-round destination, most local businesses say they are busiest with tourists between Memorial and Columbus days. The latter is Oct. 8.

Island Explorer carried 581,305 riders in 2017, which was 1 percent above 2016, 9 percent higher than 2015 and 16 percent higher than 2014. The summer average in 2017 was 6,591 riders per day, according to the service’s website.

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One number appears to have declined. The one-day peak in 2017 was Aug. 9, with 9,887 riders. This year, it appears to be Aug. 8, with 9,602 passengers, Murphy said.

Island Explorer’s propane-powered fleet of 30 buses, each with 28 seats, is funded by public and private entities, including Acadia, several Hancock County towns and L.L. Bean, which has given the service $1 million grants annually for the past five years. Established in 1999, the bus service is estimated to have carried a total of more than 6 million passengers.

No one factor is likely for the increase, Murphy said. An unusually dry and warm summer, expanding cruise-ship traffic and a good national economy are among the causes.

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Island Explorer is in the process of replacing its fleet by 2020. By then, the number of buses will likely increase to 34. Due this fall, Acadia’s traffic management plan will likely force the service buy more buses, Murphy said.

Island Explorer, which usually hires 110 to 115 drivers for the season, hired 112 seasonals this year to compliment its year-round full- and part-time staff of 15, Murphy said.

Finding enough seasonal drivers is always difficult. That’s why the service has developed staff exchanges with drivers at ski resorts in Colorado, which obviously are busiest in the winter months.

“We have drivers from Alaska, too,” Murphy said. “You have people who follow the sun.”

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