A 1.1 mile-long tunnel is credited with converting Zion National Park from an isolated and rarely visited park, to one of the most popular sites in the National Park Service system.
In the 1910s, Zion National Park was well off the beaten path. In the 1920s, the nation’s railroads — including Union Pacific — were laying down track to connect the nation’s major cities to national parks. The railroads were building lodges in these parks and mounting all-out publicity campaigns to entice visitors to come see the splendors of the West.
Zion Canyon was accessible to the west via rough dirt roads that led to a railroad spur over 80 miles away in Cedar City. Union Pacific buses ferried visitors into Zion Canyon.
Yet traveling to the east was so rugged, involving some of the tallest cliffs and deepest gorges in the nation, that building a new road would be either impossible or prohibitively expensive. Park Service officials envisioned a giant loop of roads that would allow tourists to visit Zion, Bryce Canyon, Canyonlands and the Grand Canyon in the Southwest.
It took the combined efforts of the Union Pacific Railroad, National Park Service, Utah Road Commission, and Bureau of Public Roads to make the Zion-Mt. Carmel Road a reality.
In the early 20s, engineers started looking at various routes, ultimately picking one up Pine Creek Canyon, which included steep switchbacks climbing 800 feet over loose rock. They then designed a tunnel that followed the profile of the Pine Creek Canyon wall at a distance of 21 feet from the outside face of the rock to the center line of the tunnel. Big windows were carved out of the rock, not only for light and ventilation (and spectacular views), but as places where loose rock could be dumped into the canyon below.
(There used to be parking at the tunnel windows or galleries, but eventually the tunnel became so busy that parking at the tunnel windows was closed for safety reasons.)
As vehicular volume increased, as well as the size of buses and RVs, the tunnel had more and more accidents.
A study by the Federal Highway Administration in early 1989 found that large vehicles could not negotiate the curves of the tunnel without crossing the center line. To insure safety, the National Park Service began an escort (traffic control) service in the spring of that year.
Rangers posted at both ends of the tunnel convert two-way tunnel traffic to one-way for larger vehicles, insuring safe passage. This service, for which a $15 dollar fee is charged, was provided for over 28,640 oversized vehicles in calendar year 2009.
Any vehicle that is 7 feet 10 inches in width and/or 11 feet 4 inches in height or larger is required to have a tunnel escort. Prohibited vehicles include those over 13 feet 1 inch tall, semi-trucks, vehicles carrying hazardous materials, vehicles weighing more than 50,000 pounds, single vehicles over 40 feet long, or combined vehicles over 50 feet long. Bicycles and pedestrians are also banned from the tunnel, which has no artificial lighting.
