Dead cows were left strewn across a Utah road after flying off a highway bridge when a truck overturned on one of America's busiest travel days of the year, the day before Thanksgiving.

Around 25 cows fell from an overpass onto motorists on the highway below, when the cattle truck they were in overturned on a ramp in Riverdale. Utah Highway Patrol troopers believe the truck driver was speeding above the 45mph limit at the time of the crash. "The load of cattle shifted and the semi rolled," they said in a statement.

The horrifying scene took place after the truck was turning on a curved exit ramp on Interstate 84 and hit a low wall. The truck then turned onto its side and its trailer was left teetering on a guardrail. Twenty-five cows spilled out onto Interstate 15 below.

It is unclear how many cows died in the crash. Some were able to wander away to nearby ditches and were later corralled. No people, including the cattle truck driver, were injured but there were miles of tailbacks while the scene was cleaned up.

Motorist Kerri Kofoed told Deseret News that she was driving south on Interstate 15 in the left lane when "a big black blob came flying at the windshield". Her car hit the central reservation, spun forward, drove over the cow and eventually came to a stop.

Kofoed said she felt "major gratitude that just one cow hit me and that it didn't bust through the windshield," especially as several other cows landed just behind her vehicle.

A very similar incident took place near the same highway ramp in January 2016, when "many cattle" were killed as a semi-truck tipped onto its side. Sergeant Todd Royce from Utah Highway Patrol said at the time: "Whenever we have a semi turn over, it's pretty difficult. It just makes it that much more difficult when it's live animals."

A statement from the force said the particular ramp is clearly marked for traffic to slow for a gradual left turn and merge onto Interstate 84. They said the driver in the 2016 incident had also been travelling "too fast to safely negotiate the overpass".