That crash happened in February of last year when a Mack Truck slammed into the side of the bus at the intersection on Burlington County Road 660.
Following a three hour hearing Tuesday, investigators released their findings into the cause of this fatal Chesterfield school bus crash.
Never before released details identify the primary cause focusing on both the bus driver, John Tieman, and the driver of the Mack truck.
"The probable cause of the Chesterfield, New Jersey crash was the school bus driver's failure to observe the Mack Truck which was approaching the intersection within a hazardous proximity," NTSB Managing Director David Mayer said.
Investigators say the 66-year-old bus driver admitted to having only five hours of sleep in the nights proceeding the accident, and of drinking alcohol until 11:30 the night before.
Tieman had only started driving a bus three weeks earlier. Investigators say, in his medical review, he failed to divulge he was taking the anti-anxiety prescription Clonazepam, an anti-depressant, and a prescription pain reliever for a chronic condition.
"Based on the school bus driver's combination of medical conditions and use of multiple prescription medications, it is likely that he would not have been medically certified to drive a school bus," Mayer said.
The investigation also focused on the Mack Truck driver, who was driving 10 miles above the speed limit, carrying an overweight load, in a truck with failing breaks.
"It really translates into a couple of things, increased crash forces, but it also translates to reduced breaking," Robert Sumwalt of NTSB said.
Investigators praised the New Jersey law that requires lap belts in school buses. But their findings showed the 11-year-old who died, Isabelle Tezsla, was not buckled in.
"School buses are really very safe. School children are only at risk if the school bus is hit by something very large, like a train, or what we are talking about in these cases - heavily loaded large trucks," Kristin Poland, Ph.D. of the NTSB said.
The NTSB today issued 32 findings and 12 recommendations. One of the recommendations is a push for new safety technology that allows vehicle to talk to one another.
These computers can monitor location, and speed of other oncoming drivers, and issue danger warnings before a driver can even see the other vehicle.