The cost of getting into some national parks increases on Thursday.

The rates will go up despite the fact that visitation at parks is up, which means bigger crowds, congested traffic and busier visitor centers. But more people aren't translating into a big boost for park budgets. For example, visitation at Rocky Mountain National Park in Colorado is up 20 percent so far this year and Yosemite, Yellowstone and Zion are also seeing double-digit increases. The parks are also seeing the strain. About 100 parks are planning an entrance fee hike.

Kyle Patterson, spokeswoman for Rocky Mountain National Park, says the last increase was in 2009.

"When you're a park that's been around for 100 years, you have an old infrastructure, and for us that's paved roads, unpaved roads, trails system," she says.

But the extra money from increased entrance fees will be a drop in the bucket. Overall, for example, Rocky Mountain National Park estimates it has nearly $70 million in maintenance needs. Across the country's national parks there's an estimated $11.5 billion needed to cover upkeep.

"That's run-down visitors' centers, that is unmaintained trails and crumbling roads," says Emily Douce with the National Parks Conservation Association.

Next year marks the 100th anniversary of the National Park Service. That means welcoming even bigger crowds, and Douce hopes a bill recently introduced in Congress will ease the financial strain.

"Unfortunately, over the last several years, Congress has not put the money toward getting these parks ready for the next century of service to the American people," Douce says.

President Obama voiced support for the bill. A key aspect of it would match public and private dollars, an idea first floated under the George W. Bush administration. An era of tight budgets and gridlock in Congress makes the bill a hard sell. Proponents like Douce hope the anniversary will galvanize support.

The bill would also raise the rate for a senior citizen pass — which is currently $10 for a lifetime pass — as a way to boost national park funding by an estimated $1.5 billion.

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