Safety investigators said Tuesday that a bus was traveling 88 to 92 miles per hour when it crashed last year in Utah, killing nine and injured 43 others. Driver fatigue was likely the root cause of the crash, they said.
Investigators told the National Transportation Safety Board that the 71-year-old bus driver suffered from sleep apnea, but used a device to regulate his breathing while sleeping.
The driver also reported having head congestion for three days prior to the accident, which was probably the result of altitude sickness or a cold and which likely interfered with his sleep, investigators said.
"It's really tragic — tragic in loss of life, tragic in the injuries people suffered and tragic because, in my judgment, this accident was preventable," board members Kitty Higgins said.
The motorcoach was carrying 52 passengers returning to Phoenix from a ski vacation in Telluride, Colo., on Jan. 6, 2008 when it rounded a bend on a remote two-lane highway near the town of Mexican Hat, careened off the side of the road and rolled down an embankment.
The driver had risen at 6:45 a.m. MST that morning and had been driving nearly five hours when the accident occurred at 8:02 p.m.
Investigators said it is likely the driver's fatigue caused him to misjudge the bus' speed. The speed limit on that stretch of highway was 65 mph.
Investigators were able to determine the speed using video from cameras installed on the bus. Audio equipment on the bus also recorded a passenger yelling "slow down" to the driver.
The roof of the motorcoach was sheared off in the accident and everyone was thrown out except the driver, who was wearing the only seatbelt on the bus, and one passenger, whose leg got stuck.
The board recommended a decade ago that safety standards for motorcoach roofs be strengthened. Other motorcoach recommendations that have lingered on the board's "most wanted" list of safety recommendations include protections for occupants in rollovers.
Legislation to toughen motorcoach safety standards — including a requirement for seatbelts — died in Congress last year, but another bill has been introduced this year.
Board member Debbie Hersmann said the bus crash was the third accident the board has reviewed in the past year in which the operator suffered from sleep apnea. She said the other two were a marine and an aviation accident.