States should ban all driver use of cell phones and other portable electronic devices, except in emergencies, the National Transportation Board said Tuesday.

The recommendation, unanimously agreed to by the five-member board, applies to both hands-free and hand-held phones and significantly exceeds any existing state laws restricting texting and cellphone use behind the wheel.

The board made the recommendation in connection with a deadly highway pileup in Missouri last year. The board said the initial collision in the accident near Gray Summit, Mo., was caused by the inattention of a 19 year-old-pickup driver who sent or received 11 texts in the 11 minutes immediately before the crash.

The pickup, traveling at 55 mph, collided into the back of a tractor truck that had slowed for highway construction. The pickup was rear-ended by a school bus that overrode the smaller vehicle. A second school bus rammed into the back of the first bus.

The pickup driver and a 15-year-old student on one of the school buses were killed. Thirty-eight other people were injured in the Aug. 5, 2010, accident near Gray Summit, Mo.

About 50 students, mostly members of a high school band from St. James, Mo., were on the buses heading to the Six Flags St. Louis amusement park.

The accident is a "big red flag for all drivers," NTSB chairman Deborah Hersman said at a meeting to determine the cause of the accident and make safety recommendations.

It's not possible to know from cell phone records if the driver was typing, reaching for the phone or reading a text at the time of the crash, but it's clear he was manually, cognitively and visually distracted, she said.

"Driving was not his only priority," Hersman said. "No call, no text, no update is worth a human life."

The board is expected to recommend new restrictions on driver use of electronic devices behind the wheel. While the NTSB doesn't have the power to impose restrictions, it's recommendations carry significant weight with federal regulators and congressional and state lawmakers.

Missouri had a law banning drivers under 21 years old from texting while driving at the time of the crash, but wasn't aggressively enforcing the ban, board member Robert Sumwalt said.

"Without the enforcement, the laws don't mean a whole lot," he said.

Investigators are seeing texting, cell phone calls and other distracting behavior by operators in accidents across all modes of transportation with increasing frequency. It has become routine for investigators to immediately request the preservation of cell phone and texting records when they launch an investigation.

In the last few years the board has investigated a commuter rail accident that killed 25 people in California in which the train engineer was texting; a fatal marine accident in Philadelphia in which a tugboat pilot was talking on his cellphone and using a laptop; and a Northwest Airlines flight that flew more than 100 miles past its destination because both pilots were working on their laptops.

The board has previously recommended bans on texting and cell phone use by commercial truck and bus drivers and beginning drivers, but it has stopped short of calling for a ban on the use of the devices by adults behind the wheel of passenger cars.

The problem of texting while driving is getting worse despite a rush by states to ban the practice, Transportation Secretary Ray LaHood said last week. In November, Pennsylvania became the 35th state to forbid texting while driving.

About two out of 10 American drivers overall - and half of drivers between 21 and 24 - say they've thumbed messages or emailed from the driver's seat, according to a survey of more than 6,000 drivers by the National Highway Traffic Safety Administration.

And what's more, many drivers don't think it's dangerous when they do it - only when others do, the survey found.

At any given moment last year on America's streets and highways, nearly 1 in every 100 car drivers was texting, emailing, surfing the Web or otherwise using a handheld electronic device, the safety administration said. And those activities spiked 50 percent over the previous year.

The agency takes an annual snapshot of drivers' behavior behind the wheel by staking out intersections to count people using cellphones and other devices, as well as other distracting behavior.

Driver distraction wasn't the only significant safety problem uncovered by NTSB's investigation of the Missouri accident. Investigators said they believe the pickup driver was suffering from fatigue that may have eroded his judgment at the time of the accident. He had an average of about five and a half hours of sleep a night in the days leading up to the accident and had had fewer than five hours of sleep the night before the accident, they said.

The pickup driver had no history of accidents or traffic violations, investigators said.

Investigators also found significant problems with the brakes of both school buses involved in the accident. A third school bus sent to a hospital after the accident to pick up students crashed in the hospital parking lot when that bus' brakes failed.

However, the brake problems didn't cause or contribute to the severity of the accident, investigators said.

Another issue involved the difficulty passengers had exiting the first school bus after the accident. The bus' front and rear bus doors were unusable after the accident - the front door because the front bus was on top of the tractor truck cab and too high off the ground, and the rear door because the front of the bus had intruded five feet into the rear of the first bus.

Passengers had to exit through an emergency window, but the raised latch on the window kept catching on clothing as students tried to escape, investigators said. Exiting was further slowed because the window design required one person to hold the window up in order for a second person to crawl through, they said.

It was critical for passengers to exit as quickly as possible because a large amount of fuel puddled underneath the bus was a serious fire hazard, investigators said.

"It could have been a much worse situation if there was a fire," Donald Karol, the NTSB's highway safety director, said.