The National Park Service is looking to substantially raise the admission price for some of the country’s most popular national parks--a move that could put visiting them out of the reach of many Americans.

The proposal calls for entrance fees for private vehicles at 17 parks to increase from $25 or $30 during peak season to $70. People entering the parks on foot would pay $30 (up from $10-$15). And motorcycles would jump from $15-$25 to $50.

The Park Service says the additional revenue would be used for infrastructure improvements.

"The infrastructure of our national parks is aging and in need of renovation and restoration," said Ryan Zinke, U.S. Secretary of the Interior. "We need to have the vision to look at the future of our parks and take action in order to ensure that our grandkids’ grandkids will have the same if not better experience than we have today. Shoring up our parks’ aging infrastructure will do that."

The increase would affect 17 parks around the country:

1. Acadia

2. Arches

3. Bryce Canyon

4. Canyonlands

5. Denali

6. Glacier

7. Grand Canyon

8. Grand Teton

9. Joshua Tree

10. Mount Rainier

11. Olympic

12. Rocky Mountain

13. Sequoia & Kings Canyon

14. Shenandoah

15. Yellowstone

16. Yosemite

17. Zion

The proposal will be open for public comment at the National Park website for 30 days. But some park advocates are already speaking out against it.

"We should not increase fees to such a degree as to make these places--protected for all Americans to experience-- unaffordable for some families to visit,” said Theresa Pierno, President and CEO of National Parks Conservation Association. "The administration just proposed a major cut to the National Park Service budget even as parks struggle with billions of dollars in needed repairs. If the administration wants to support national parks, it needs to walk the walk and work with Congress to address the maintenance backlog.”