Vehicle size restrictions are coming to the Zion-Mount Carmel Highway at Zion National Park/NPS file

Beginning in 2026, restrictions being placed on the size of vehicles traveling the Zion-Mount Carmel Highway at Zion National Park in Utah will lead to some vehicles being rerouted to other entrances and exits of the national park.

The changes reflect discussions with departments of transportation, neighbors, elected officials, business owners, and many other stakeholders, park officials said in a release Thursday.

Beginning in mid-2026, the park plans to reroute vehicles that exceed 11’4” tall, 7’10” wide, 35’9” long, or 50,000 pounds to routes other than the Zion-Mt. Carmel Highway (the road across Zion National Park). Vehicles that exceed these specifications can use existing alternate routes surrounding the park.

These changes aim to help reduce: 

• collision likelihood. 

• overweight transits on road bridges. 

• lane-crossing due to vehicles being too long to negotiate turns. 

“These changes reflect months of discussions to find the best way forward to manage the historic Zion-Mt. Carmel Highway and increase driver safety,” said Zion Superintendent Jeff Bradybaugh. “Our goal is to protect drivers, meet modern safety standards and ensure the integrity of the road and tunnels so that we continue to enjoy scenic drives on the historic Zion-Mt. Carmel Highway.” 

Park officials said the two-year lag in implementing the restrictions was necessary both to ensure the public is aware of the change and so tour companies, which plan their routes 18 months to 2 years in advance, have ample time to adjust their itineraries as needed.

Vehicles that exceed the listed specifications listed will still be able to enter the park and drive on open roads. If they are too large to safely drive on the Zion-Mt. Carmel Highway, they can drive around the park on existing roads, which will add an estimated ten to 40 minutes, depending on route and destination. In the years to come, regional partners are also discussing improvements to roads around Zion that should simplify travel, the park release said.

Engineering and traffic studies regarding contemporary road use show that travel by many large vehicles presents public safety concerns, according to the National Park Service. In addition to exceeding engineering limits on park bridges, large vehicles like recreational vehicles or motorcoach buses cross the centerline in 18 locations where the serpentine road’s turning radius cannot accommodate long vehicles — which becomes problematic when vehicle length exceeds 35 feet 9 inches.   

Bridges on the Zion-Mt. Carmel Highway are rated for 50,000-pound vehicles. Some large vehicles exceed this weight. Additionally, the Zion-Mt. Carmel Tunnel requires its own restrictions. Vehicles wider than 7 feet 10 inches and taller than 11 feet 4 inches cannot pass through the tunnel while maintaining two-way traffic and require a tunnel escort. Vehicles taller than 13 feet 1 inch cannot fit through the tunnel and are not allowed.  

Historic Zion-Mt. Carmel Highway 

The Zion-Mt. Carmel Highway is a landmark listed on the National Register of Historic Places and is designated as a Historic Civil Engineering Landmark. This historic road was originally designed and constructed in the 1920s and 1930s. To complement the landscape, the road has: 

• tight turns. 

• some steep grades. 

• a large number of switchbacks. 

• relatively narrow lanes. 

• two low and narrow tunnels.  

• bridges. 

These design elements make the road more compatible with the landscape but also hard for modern, larger vehicles to travel safely. 

When the road was designed, vehicles were smaller, moved at slower speeds, and weighed far less. Expanding the historic road is not feasible because of the terrain. New construction could be prohibitively expensive and harm the park’s landscapes, plants, animals, and impact the historic values of the road itself, the park release said.