A lot has changed since Zion-Mt. Carmel Highway opened in 1930.
For one, Zion National Park welcomed just 55,297 visitors that year. Ninety-three years later, that number jumped to 4.6 million.
The cars on the park's primary highway looked different, too.
The 1930 Ford Model A was a little more than 12 feet long. The recreational vehicles and buses that carry many visitors today can easily be three times that length.
As he stood on a red rock ledge overlooking an especially sharp curve on the park’s east side, Jonathan Shafer of the National Park Service said it’s not hard to see how that’s become a problem.
“No driver is able to make that turn without getting really close to skirting, or in the case of the driver who just went by, going right over the double yellow line.”
Safety concerns are a big part of why Zion will close the 25-mile two-lane road to vehicles longer than 35 feet 9 inches in mid-2026. That means many tour buses, RVs and trailers will need to drive the long way around the park rather than through it.
The new rule will also make the highway off-limits to vehicles taller than 11 feet 4 inches, wider than 7 feet 10 inches and weighing more than 50,000 pounds. Oversized vehicles will still be allowed to park at the Zion Canyon Visitor Center, Shafer said, where visitors can hop on the shuttle system.
The decision is the result of recent engineering and traffic studies the park completed with the Federal Highway Administration, as well as discussions between Zion and local leaders in neighboring areas. The studies reported the highway has more than a dozen dangerously sharp curves, including several of the hairpin turns that lift drivers from the floor of Zion Canyon toward the historic Mt. Carmel tunnel.
“We're making evidence-based decisions based on the geometry of this road and the weight restrictions of the bridges that are on it so that we can ensure that we reduce the likelihood of collisions, that we improve safety and that we reduce the number of overweight transits,” Shafer said.
Barbara Bruno, mayor of the Zion gateway town Springdale, was one of the local leaders included in discussions.
The main concern from other community leaders, she said, was that the new rule might negatively impact local economies if drivers choose to skip the area altogether. But with how popular Zion has become, Bruno isn’t worried about taking that chance, especially when it’s for the sake of safety.
“If someone's coming to Zion, they will not be deterred by a little bit of a detour [or] a little bit of a longer time to get there.”
The move could also free up some gridlock at the highway’s historic tunnel, she said.
Currently, rangers have to halt traffic each time an oversized vehicle needs to pass through — something the park has done since the 1980s. This allows the vehicle to drive in the middle of the road to avoid hitting the tunnel’s curved ceiling, but it forces others to wait while it's escorted through.
For Springdale residents, a trip across the Zion-Mt. Carmel Highway is often just a way to get to the other side, Bruno said, rather than a day at the park. So being consistently held up makes things tricky. Residents often weigh the chance of sitting in line at the tunnel against taking a different highway, such as State Route 59.
“The thing I heard most from Springdale residents when they heard about the plan to close the tunnel to oversize traffic was: ‘It's about time.’”
In peak summer season, around 100 oversized transits cross the highway each day, Shafer said. Because of that, tunnel traffic is halted for an average of 45 minutes every hour.
The park understands the restrictions will affect the way people visit in the future, he said, but it had to weigh that against what’s best for the majority of its visitors. And the rule’s two-year roll-out will hopefully allow tour groups to plan accordingly.
The park even considered changing the road’s design to allow for larger vehicles, Shafer said. Ultimately, however, it decided that would take too much away from the natural landscape and the way the road’s twists and turns complement it.
“The reality is that building a road that could accommodate very large vehicles, like what you might see on a freeway, would make the road here look a lot more like a freeway. So we want to take action to conserve the experience here.”
