The U.S. lawsuit, filed by Jong-Hyun Chae and Seong-June An, claims the bus driver violated American federal laws by working 90 to 100 hours during the first eight days of the trip from Las Vegas to British Columbia.
The lawsuit, which names Mi Joo Tour and Travel Ltd. of British Columbia, was filed Monday in a Tacoma, Wash., court.
It alleges the tour company's driver was fatigued, ignored warnings of poor conditions, and didn't slow down when he encountered ice-coated roads.
The bus, with 48 people on board, slid out of control on Interstate 84 east of Pendleton, Ore., in an area known as Deadman Pass.
After the driver lost control, the bus spun 360 degrees then burst through the guard rail, careened down a steep embankment, flipped end to end and then crashed near a cliff, the lawsuit said.
Nine of those aboard were killed, while 38 others were hurt.
At least one of the victims, 55-year-old Seokmin Moon, was Canadian, while seven Canadians were injured. Most of the other victims were from the United States or from Korea.
The boys' lawyer, Charles Herrmann, said even if the driver worked every day during the eight-day tour, he would only have been allowed a maximum of 70 hours under U.S. law. Instead, Herrmann alleges, the driver was working 10 to 12 hours for the first six days and then 27 hours in the two days before the crash.
"When you drive like that everyday, basically on your ninth day, you're tired. He went by three different reader-board signs that told him that the roadway ahead was dangerous."
The bus tour started in Vancouver and made stops in Oregon, California, Arizona and Idaho before the return trip which ended with the crash in Oregon.
"Mi Joo Tour was actively negligent in that it knowingly caused or permitted (the driver) to violate the requirements of the maximum driving time for passenger-carrying vehicles," the lawsuit said.
The civil lawsuit was filed Monday and issued an automatic trial date of Jan. 6, 2014, although Herrmann said such trial dates are often delayed.
Herrmann said he has spoken with other passengers who were on the bus that day, but so far, only the two young men were willing to go ahead with a lawsuit.
"Everybody that I've talked to who was on the bus was concerned about how fast (the driver) was driving, given the conditions."
The 54-year-old bus driver, a deacon at a Methodist church in Surrey, B.C., was among the 38 people hurt in the crash. He is not named as a defendant in the lawsuit.
Days after the Dec. 30 crash, police in Oregon said it would be at least a month before they might announce if the driver would face any charges.
The lawsuit claims the 15- and 16-year-old boys fainted or were knocked unconscious after the bus crashed and awoke to a nightmarish scene of dead passengers and others who'd been wounded and were screaming all around them.
Herrmann, who works with war veterans who have post-traumatic stress disorder, said there are similarities between war veterans and those involved in such a crash.
"To wake up after being knocked unconscious, there's dead people around you, people are screaming, people are bleeding, strewn out in the snow, pinned in their seats and so on," he said.
"It's a very serious issue, the emotional trauma, as well as talking about the physical injuries. To be in the snow, freezing, it was a terrifying experience for all of them."
None of the charges have been proven in court and the company has yet to file a statement of defence.
When reached for comment on Monday the company's owner Edward Kang referred all calls to his lawyer, who didn't return a request for an interview.
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