FLAGSTAFF, Ariz. (AP) — A tour bus crash that killed seven people on a rural Arizona highway last year might have been prevented had past safety recommendations been implemented, the National Transportation Safety Board said Tuesday.

Board members strongly suggested that the National Highway Traffic Safety Administration require more protections for passengers traveling in mid-size commercial buses in the form of restraints and strengthening windows and roofs to keep passengers from being ejected. The same recommendations were made more than a decade ago, the board noted.

"More can and must be done to protect medium-size bus passengers," said NTSB Chairwoman Deborah Hersmen. "The tragedy of this accident isn't that we haven't known what to do, we haven't done it."

The charter bus was carrying a group of Chinese tourists on a return trip to Las Vegas from the Grand Canyon on Jan. 30, 2009, when it crashed on U.S. 93 near Hoover Dam.

The driver was attempting to fix a problem with airflow through his door before the crash and became distracted, which the NTSB cited as the probable cause.

Investigators said the driver then veered onto the right shoulder and overcorrected, crossing a desert median and overturning. The bus rolled at least once — ejecting 15 of its 17 passengers out of the windows — before coming to rest on its side.

The tour guide and six Chinese tourists were killed. Ten others were injured, including the driver, who worked for carrier D.W. Tour & Charter of San Gabriel, Calif. The tourists had flown from Shanghai to San Francisco before traveling to Las Vegas and the Grand Canyon.

Adding to the severity of the accident was the lack of stability control and lane departure warning systems. NTSB recommended that all new commercial vehicles exceeding 10,000 pounds be required to have them.

The board has long advocated for the use of recording devices to capture data in buses and added that to its list of recommendations yet again. The recorders could capture braking and acceleration patterns, air bag deployments and steering that would help re-create crashes.

The board also wants the definition of buses that varies across federal agencies clarified so any new regulations can be standardized.

The board investigates accidents and makes safety recommendations.

The traffic safety administration, which sets regulations, is developing a motor coach safety plan but it's unclear whether that would include commercial vehicles like the tour bus involved in the Arizona crash. A call to NHTSA on Tuesday wasn't immediately returned.

Peter Pantuso, president and chief executive of the American Bus Association, said the NHTSA plan is focused more on larger coaches and not the type of bus involved in the Arizona crash. Those buses typically are used for shuttles in the hotel industry, or park-and-ride operations.

"I would imagine at some point they will look at that," he said.

The Obama administration has been pushing for a review of bus safety that would include long-sought safety requirements for buses, including seatbelts and stronger roof standards.

The driver of the tour bus in Arizona had the only seatbelt on the bus, but he wasn't wearing it at the time. The bus sustained damage to the front fenders, the passenger loading door, 9 out of 10 windows were broken out. Despite rolling, the roof was largely intact.

The Arizona Department of Public Safety said in a statement Tuesday that its investigation "did find the driver made very poor judgment in his actions, which created an unsafe operation of the tour bus and led to the deaths."

DPS officials said their findings were forwarded to the Mohave County Attorney's Office, which determined the actions of the driver did not meet the criteria or threshold necessary for formal criminal charges.