DENVER – The National Park Service proposed peak-season entrance fee increases on Tuesday at 17 of its most popular attractions, including Yellowstone, Grand Canyon and Yosemite national parks, to help finance a backlog of maintenance and improvements.

U.S. Interior Secretary Ryan Zinke said the proposal, including a hike in vehicle admission fees from $30 to $70 at some parks, would generate $70 million annually, marking an increase of nearly 34 percent in collections for the park system as a whole.

“The infrastructure of our national parks is aging and in need of renovation and restoration,” Zinke said in a statement. “Targeted fee increases at some of our most visited parks will help ensure that they are protected and preserved in perpetuity.”

The additional revenues would be earmarked for deferred maintenance to roads, bridges, campgrounds, bathrooms and water lines at 17 of the fee-charging units of the Park Service, an agency of the Interior Department.

The majority of national parks will remain free to enter. Only 118 of the 417 Park Service-administered sites currently charge for admission.

Under the proposal, peak-season visitor fees for the 17 affected parks would increase in 2018 to $70 for non-commercial automobiles, $50 per motorcycle and $30 per person for visitors entering on foot or on bicycles.

Theresa Pierno, president of the Washington-based National Parks Conservation Association, blasted the proposal, saying the increases would make the parks unaffordable for some and shift a greater portion of the costs of park improvements to visitors.

“The administration just proposed a major cut to the National Park Service budget even as parks struggle with billions of dollars in needed repairs,” Pierno said in a statement.

Three of the best known parks on the list – Yosemite in California, the Grand Canyon in Arizona and Yellowstone in Wyoming, Montana and Idaho – saw entrance fees raised as recently as 2015, the association said.

In addition to further hikes at those parks, higher fees would be charged at such popular Western destinations as Denali National Park in Alaska, Rocky Mountain National Park in Colorado, Bryce Canyon, Zion, Arches and Canyonlands national parks in Utah, and Mount Ranier and Olympic national parks in Washington state.

The only two units affected in the Eastern United States are Shenandoah National Park in Virginia and Acadia National Park in Maine.

Federal law requires that 80 percent of revenue generated at a national park remains where it is collected. The remaining funds can be funneled to other projects within the system.

Pierno said her organization favored a bill in Congress that she said would address deferred maintenance in “a more substantial and sustainable” manner.