WASHINGTON, D.C. — The National Transportation Safety Board (NTSB) determined that last year's fatal tour bus accident near Dolan Springs, Ariz., was a result of the driver being distracted by his manipulation of the driver's side door as the vehicle was traveling about 70 mph on a divided highway.

As the driver attended to the door, the vehicle drifted out of its lane. The driver then made an abrupt steering maneuver to correct the drift resulting in a loss of directional control of the medium-sized bus.

The accident occured on Jan. 30, 2009, when the 2007 Chevrolet/Starcraft 29-passenger bus, operated by DW Tour and Charter and carrying 16 passengers and the driver, crashed on U.S. Highway 93 on a return trip from Grand Canyon West to Las Vegas. The bus came to rest on the southbound side of the four-lane divided highway after veering out of its northbound lane, crossing the median and rolling over. Seven passengers were killed, while nine passengers and the driver sustained minor to serious injuries.

In its investigation, the NTSB found that other factors, in addition to the driver's failure to maintain control of his vehicle, contributed to the accident and its severity.

Had the vehicle been equipped with a lane departure warning system, the driver would have been alerted upon the initial drift from the driving lane. A stability control system, already widely used in automobiles, could have reduced the likelihood of the driver losing control of the bus and rolling over.

The NTSB determined that because the U.S. Department of Transportation has yet to establish consistent classifications for each bus body type in operation, it is unclear whether current bus safety initiatives affect medium-sized buses. The NTSB also found that if there were federal standards addressing occupant protection, roof strength and window-glazing, the likelihood of catastrophic outcomes in medium-sized bus and motorcoach rollovers would be reduced.

From this investigation the NTSB made the following recommendations to the National Highway Traffic Safety Administration (NHTSA):

• Require new commercial vehicles exceeding 10,000 pounds to be outfitted with lane departure warning systems, stability control systems and safer overhead luggage racks.

• Develop standard regulatory classifications and definitions for all bus body types.

• Include all buses above 10,000 pounds, other than school buses, in rulemaking on occupant protection, roof strength and window glazing; and require all buses above 10,000 pounds to be equipped with data recording systems.

A synopsis of the Board's report, including the probable cause, conclusions and recommendations, is available on the NTSB's Website.

The NTSB's full report will be available on the Website in several weeks.