The National Park Service has reduced the number of free days at its more than 400 locations from 10 in 2017 to four in 2018.

Free days during the coming year are Jan. 15 for Martin Luther King Jr. Day; April 21, the first day of National Park Week; Sept. 22, for National Public Lands Day; and Nov. 11 for Veterans Day.

The entrance fee waiver for the free days does not cover amenity or user fees for activities such as camping, boat launches, transportation or special tours, according to a news release.

Perhaps the best deal to enjoy national parks and other federal lands is to purchase an $80 annual America the Beautiful National Parks and Federal Recreational Lands Pass, which allows unlimited entrance to more than 2,000 federal recreation areas. Discounted or free passes are available for senior citizens, current members of the military, families of fourth-grade students and disabled citizens.

Visit the National Park Service’s website at nps.gov/planyourvisit/passes.htm for more information.

The Park Service charges weekly entrance fees of $25 or $30 per vehicle at 118 of the 417 national parks. The Park Service has proposed raising the cost to $70 at 17 busy parks mainly in the West, including Yellowstone, Grand Canyon, Yosemite and Zion.

The agency estimates the increase would generate an additional $70 million to help address backlogged maintenance and infrastructure projects. Opponents, including attorneys general from 10 states, say the higher costs could turn away visitors and might not raise that much money.

The Park Service didn’t explain why it was cutting back on free days. An Interior Department spokeswoman didn’t immediately respond to a request for comment.

“The days that we designate as fee-free for national parks mark opportunities for the public to participate in service projects, enjoy ranger-led programs, or just spend time with family and friends exploring these diverse and special places,” National Park Service Deputy Director Michael T. Reynolds said in a statement.

A group opposed to raising fees criticized the change.

“Not everyone can book a helicopter or charter a boat when they want to visit our national parks,” said Jesse Prentice-Dunn with the Denver-based Center for Western Priorities in a release. “America’s parks must remain affordable for working families.”

The Associated Press contributed to this story.