A new development has been made in the investigation of the car crash that left Tracy Morgan with debilitating injuries and killed his friend, James “Jimmy Mack” McNair.

According to The Associated Press, the National Transportation Safety Board has concluded the Walmart truck driver who slammed into a limo van carrying the 46-year-old star and his friends caused the accident because he had not slept in 28 hours.

tracy morgan

Tracy at a New York Yankees game on Tuesday, Aug. 4.

The board claimed driver Kevin Roper failed to adhere to warning signs to slow down while traveling on the New Jersey turnpike. Had the driver decreased his speed to the suggested 45 mph, he would have been able to stop the truck before it hit the limo van and caused the crash, the AP reported.

RELATED: Tracy Morgan Makes First Major Public Appearance Since Car Accident at Yankees Game — See the Pics!

“One tragic aspect of roadway death is that so often they could have been prevented,” Chairman of the Safety Board, Chris Hart, said in a statement.

kevin roper

Walmart truck driver Kevin Roper.

Tracy suffered a broken leg, nose and ribs in addition to a traumatic brain injury in the June 2014 crash. The star then spent 10 days in the ICU before entering a rehab facility to undergo extensive physical therapy.

“I’ve been down… there are times where I have my good days and my bad days, where I forget things,” he said in a previous interview of his continued recovery. “Right now my goal is just to heal and get better.”

Following the incident, Roper was charged with death by auto and four counts of assault by auto.