A Greyhound driver who authorities say fell asleep before the bus careened off a road in the Utah desert two years ago was tired, sick and should never have been behind the wheel, according to a new lawsuit over the crash that killed one person and injured 12 others.

Bus driver Charles E. Saunders fell asleep after taking cold medicine and never hit the brakes as the bus flew off a highway and crashed into a canyon wall about 300 miles (483 kilometers) south of Salt Lake City, the lawsuit says. Michael Edwards of Georgia filed the claim Monday in a court in Nevada, where Saunders lives.

Edwards said he suffered a traumatic brain injury and fractures to his face, elbow, ribs and tibia and has racked up more than $500,000 in medical expenses. He is seeking damages to cover those costs as well as other economic losses from his injuries.

He asserts that Saunders requested a replacement driver for the route from Green River, Utah, to Las Vegas on New Year's Eve 2017 because he was feeling sick but that Greyhound didn't send one.

Greyhound spokeswoman Crystal Booker declined to comment, citing company policy during lawsuits. It's unknown if Saunders has an attorney, and no listed phone number could be found for him.

The lawsuit says Saunders had fallen asleep about 45 minutes before the crash and a passenger woke him up. Shortly before the crash, a passenger yelled at Saunders: "Driver! You're sleeping!"

The bus flew off Interstate 70 and over a small ravine, hit a canyon wall and spun 180 degrees, the lawsuit says. While some passengers crawled out and tried to get help, others were pinned in the bus and couldn't move, Edwards' lawyers said.

Summer Pinzon, 13, of Azusa, California, was killed in the late-night crash.

Utah police said after the crash that they were investigating it as a possible negligent homicide case after finding cold medicine at the scene and getting reports that the driver was slumped over the wheel. Online Utah court records indicate Saunders was not charged with a crime.

A phone message left with Emery County Attorney Mike Olsen wasn't immediately returned.