WASHINGTON – The highway crash that severely injured comedian Tracy Morgan and killed another comedian last year raises significant safety issues involving driver fatigue and truck safety, federal accident investigators said Tuesday

The Wal-Mart truck driver who slammed into the back of a limousine-van in which Morgan and several other entertainers and friends were riding had been awake for the previous 28 hours, National Transportation Safety Board investigators said at a meeting to determine the cause of crash and to make safety recommendations.

The driver, Kevin Roper of Jonesboro, Ga., could have prevented the crash if he had slowed to 45 mph, the posted speed limit for the construction work zone on the New Jersey Turnpike where the crash occurred, investigators said. Investigators have said the truck was traveling at 65 mph and that it was slow to react to a sign lowering the speed limit to 45 mph in a construction zone. They also have said the truck was traveling at a rate of speed of 47 to 53 mph when it hit the limousine.

Instead, they said, the truck struck the rear of the limo at a higher speed, starting a chain reaction crash that affected 21 people in six vehicles.

“One tragic aspect of roadway deaths is that so often they could have been prevented,” said NTSB Chairman Chris Hart.

Investigators also said the limousine-van had been customized, and that a sheet of plywood that had been installed to separate the cab from passengers blocked occupants from escaping the vehicle after the crash. They were also critical of the emergency response to the crash.

Comedian James “Jimmy Mack” McNair of Peekskill, N.Y., a mentor of Morgan’s, was killed. Morgan suffered head trauma, a broken leg and broken ribs, and was in a coma for two weeks. Three other passengers in the limo suffered serious injuries.

Morgan, a former “Saturday Night Live” and “30 Rock” star, and the others were returning from a show in Dover, Delaware.

Roper was charged with death by auto and four counts of assault by auto in state court in New Jersey. The criminal complaint alleged Roper operated the truck “without having slept for a period in excess of 24 hours resulting in a motor vehicle accident.” A person can be charged with assault by auto if he or she causes injury after knowingly operating a vehicle after being awake for more than 24 hours under New Jersey law.

The safety board has long raised concerns about operator fatigue leading to accidents across all modes of transportation, from airline pilots to train engineers.

In May, Morgan and two friends injured in the crash settled a lawsuit against Wal-Mart for an undisclosed amount. The Bentonville, Arkansas-based company settled a wrongful death claim filed by McNair’s children for $10 million, according to court papers.

Using a cane, Morgan made his first public appearance this June on NBC’s “Today” show and said he hoped to resume his career but that he wasn’t 100 percent healed. He hasn’t performed since the accident.