BAR HARBOR — From May 26 to Oct. 19 the National Park Service is requiring advanced vehicle reservations to access Acadia National Park’s Cadillac Summit Road. The reservation system, originally tested by the service last summer, is an effort to protect Cadillac Summit’s natural environment and avoid overcrowding of the parking lot.

To make a reservation to access Cadillac Mountain by car, visit recreation.gov/timed-entry/400000?tab=tours. From there, people can choose either sunrise (3:30 a.m.) or one of the various daytime slots (time slots are available every half-hour from 6:30 a.m. until 8 p.m.).

The cost is $4 per vehicle, plus a $2 reservation fee. Once the vehicle reservation is booked, visitors should save the confirmation code and purchase a park pass at recreation.gov/sitepass/74271.

Thirty percent of available vehicle reservations are released 90 days ahead of each calendar date on a rolling basis. The remaining 70% are released at 10 a.m. two days ahead of each date, to allow visitors flexibility.

If visitors are unable to book a vehicle reservation for Cadillac Mountain, the Bar Harbor Chamber of Commerce recommends available tours at visitbarharbor.com.

For more information, visit Vehicle Reservations — Acadia National Park (U.S. National Park Service) at nps.gov/acad/planyourvisit/vehicle_reservations.htm.