In 2014, national parks received nearly 293 million recreational visitors. When the number of non-recreational visits (vendors, commuters, etc.) are added, it is easy to see that the park transportation system is under an ever-increasing burden.
As the number of visits increases, park roads will increasingly experience traffic congestion. The NPS has not been building new roads or adding lanes to alleviate congestion. Instead, it has been pursuing alternative transportation systems, which frequently include high occupancy vehicles (shuttle buses, trolleys, ferries) as a means to add capacity, alleviate congestion, improve the visitor experience, and protect our resources.
While many consider only the well-known national parks, such as Yosemite, Yellowstone, Great Smoky Mountains, and the Grand Canyon National Parks, the national park system comprises a number of different types of units, each with varying transportation needs. The graphic below shows the 2014 visitation rates for the various types of units within the national park system.
2014 NPS Visits by Unit Type
Chart Source: NPS Stats, National Park Service Visitor Use Statistics: https://irma.nps.gov/Stats/Reports/National