Wal-Mart Driver Was Awake More Than 28 Hours Before Tracy Morgan Crash: NTSB "The passengers had no available exits until emergency responders" intervened.

 -- The driver of a Wal-Mart tractor-trailer that slammed into a limo carrying comedian Tracy Morgan last June had been awake more than 28 hours, the National Transportation Safety Board said today.

Around 1 a.m. on June 7, 2014, 35-year-old Kevin Roper – then halfway through the 13th hour of his 14-hour shift – slammed into Morgan’s limo from behind, killing comedian James McNair and seriously injuring Morgan and three others.

Before starting his Wal-Mart shift, Roper had driven 12 hours in his personal vehicle from his home in Georgia to his base in Delaware, according to the NTSB.

His “decision to drive 800 miles overnight” was “a factor in the crash,” NTSB senior accident investigator Dennis Collins said today.

Though Wal-Mart provided fatigue information during its driver training, it was not required to have a fatigue management program,the NTSB said.

Moments before the crash, the trailer was traveling at 65 mph, 20 mph over the construction zone’s 45 mph speed limit.

“Had the truck driver been traveling at the posted work zone speed limit of 45 mph, it could have been stopped before impact,” NTSB investigator David Rayburn said today.

Roper's attorney told ABC News he would dispute the NTSB's conclusions.

The passengers in the rear of the limo’s rear compartment were not wearing seatbelts at the time of the crash, NTSB chairman Christopher Hart announced at a board meeting today, nor had they received a safety briefing outlining the benefits of seat belts.

After being hit by the Wal-Mart truck, the limo then struck three other vehicles and rolled over before coming to rest on its side on the New Jersey Turnpike.

Because the limo had been customized, “the passengers had no available exits until emergency responders removed parts of a plywood panel that had been installed,” Hart said today.

Indeed, it took nearly 40 minutes for first responders to extricate some of the victims from the limo.

“I shudder to think what would have happened if this vehicle had caught fire,” NTSB board member Robert Sumwalt noted.

Roper was later charged with one count of vehicular homicide and several counts of assault by auto, with authorities saying they believed he had dozed off behind the wheel. He pleaded not guilty.

The crash left Morgan, then 45, in critical condition, with multiple broken bones and a traumatic brain injury.

Since then, the comedian has “struggled” to regain his old self, his lawyer said.

In a June 2015 interview with “Today” anchor Matt Lauer, Morgan wondered through tears whether he was ever “going to be funny again.”

He filed a civil suit against Wal-Mart; they reached a confidential settlement in May.

The retailer, which initially faulted Morgan and his colleagues for not wearing seat belts, later “took full responsibility for the accident,” according to Morgan’s lawyer.