A semi-truck trailer is usually between 13 feet 6 inches and 14 feet tall. There are no federal rules about the height of semi-trucks, but some roads are lower than the average height of a commercial motor vehicle.
Semi-trucks and trailers may have height limits set by the Department of Transportation in each state. For example, the California Department of Transportation says that all semi-trucks can be no taller than 14 feet. The Pennsylvania Department of Transportation, on the other hand, says that semi-trucks can’t be more than 13.5 feet tall.
In the United Kingdom, semi-trucks can’t be taller than 13.1 feet.