Visitation to the nation’s national parks reached another record high in 2016.
Last year the NPS estimates 325 million people visited national parks which is the third consecutive year of record highs.
National Parks Service spokesman Jeffrey Olson cited the 2016 centenary year of the parks service and still low gas prices for the increase.
The Grand Canyon National Park welcomed 5.9 million visits and 4.3 million visited Yellowstone, and both parks have yet to post monthly attendance for December.
However the increase in numbers is resulting in more congestion and trash at parks and more frustration for visitors.
Motorists are experiencing wait times of an hour of more to enter parks and that is leading to more incidents of aggressive behavior.
"The level of frustration, we’ve certainly seen an increase in that. Sometimes they take it out on each other and sometimes they take it out on the park," said Kyle Patterson, Rocky Mountain National park spokeswoman.
John Marciano, Zion National Park spokesman said: "We love having people come to the park but our No. 1 goal, our mandate, is to preserve the park into perpetuity and to ensure our visitors have a safe experience."
