MDI’s Island Explorer - Why transit works in this corner of Maine

By Ben Smith, AICP

Seasonal traffic on Mount Desert Island is a real issue, with impacts felt on MDI and for miles back through Trenton and Ellsworth. Acadia National Park sees over 4 million visitors annually, with a vast majority of those visits taking place between May and October. The one-way, two-lane Park Loop Road allows parking in the right lane, which is utilized heavily in peak seasons at popular locations, resulting in large sections of one-lane road. The National Park Service began requiring timed entry passes for personal vehicles to access the Cadillac Summit Road in 2021, as traffic jams of idling cars with no way out filled the auto road. In short, visiting MDI with a car in the summer comes with inconvenience. 

The Island Explorer bus service started in 1999 and has grown steadily since. Continued investment and expansion of the service is a key piece of Acadia’s Transportation Plan, finalized in 2019. Even though the vast majority of visitors drive to MDI from points around the country, many people are happy to park their cars for the duration of their visit and use the Island Explorer. 

The Island Explorer works because:


There is frequent service and it is free. At many of the busiest destinations, like Bar Harbor Village and points along the loop road, riders rarely have to wait more than 10 minutes for a ride to their next destination. The bus is offered at no cost to riders and no reservations are required. Jump on and jump off all day long.

There are connections to key destinations inside and outside the Park. A hallmark of the service is that there are stops at places where people stay outside of the park (hotels and campgrounds), places in the park (campgrounds, trailheads, and popular destinations), and neighboring village centers like Bar Harbor, Northeast Harbor, Southwest Harbor, and Tremont. There is even a ferry to Winter Harbor and a loop around the Schoodic peninsula.

Parking is limited everywhere on MDI. Outside of the Hulls Cove Visitor Center and the new off-island Transportation Center currently being built, parking is very limited at trailheads, popular destinations in the park, and the surrounding villages. Some places like Jordan Pond and popular trails are just not accessible to many during the busiest times without the Island Explorer service.

Even though the Island Explorer is unique in Maine - it’s supported by the National Park Service primarily to provide transportation in and around a very popular national park - the success of the Island Explorer demonstrates that it’s possible to get summer tourists and people in rural areas out of their cars and onto public transit.

Lessons that other regions may learn from the success of the Island Explorer include:

In a place where housing costs are high and supply is extremely limited, the service is available to all. This service is used by tourists, seasonal workers, and year-round residents alike. This reduces traffic and parking pressure for everyone. As the service and routes continue to expand, the service is becoming more valuable to residents and seasonal workers, who may not have reliable access to a car.   

Transit must be at least as convenient as using a car for most users. With 32 busses, riders can be assured that the most popular Island Explorer routes will be served at such a regular interval that scheduling or trip planning is unnecessary. 

Road construction and rebuild projects can only get you so far. There have been some major road projects in Ellsworth and on MDI since the late 2000s aimed at increasing traffic capacity and road conditions. Of course, traffic is still an issue, and wider roads with more suburban box stores in Ellsworth do not seem to be contributing to the safety, traffic flow, or quality of these places

One agency is making decisions on land use and transportation in concert, and coordinating with municipalities and businesses. The National Park Service is tasked with managing the facilities, uses, resource protection, visitor experience, and safety within Acadia National Park, as well as the improvements and investments in the transportation system that serves those uses. In that dual role, they are making decisions that support that place more effectively than when transportation, land use, and transit decisions are made in separate agencies or governmental units that have different (and sometimes conflicting) missions, budgets, funding sources, and constituencies.