The National Transportation Safety Board said the driver lost control near Mount Pleasant, Pennsylvania, while traveling at 77 mph (124 kph) into a curve. The posted speed limit in the area is 70 mph, with a warning sign at the curve to keep below 55 mph (89 kph).
NTSB chair Jennifer Homendy said in a statement that the crash “is a tragic reminder that speed kills. But it’s about more than driver behavior, which is why our recommendations take a comprehensive approach to promote safe speeds.”
The federal agency has concluded its investigation into the chain-reaction crash that occurred at about 3:30 a.m. on Jan. 5, 2020, on a remote section of interstate about 30 miles (48 kilometers) east of Pittsburgh.
The bus was operated by Z&D Tour Inc. and headed from the New York area to Cincinnati. The bus driver and two passengers, and the driver and a passenger in a truck that slammed into it, were all killed. An occupant of another truck and 49 bus passengers were hurt.
The NTSB found that the westbound bus went off the right side of the highway, hit an embankment and overturned, blocking both lanes and the shoulder. Almost immediately two trucks that had been following the bus ran into it. A car and truck drove off the road to avoid the crash and ended up wedged beside each other.
A lawyer for Z&D Tour said Tuesday she had not seen the NTSB findings and declined comment about the crash.
The NTSB said the bus had slowed to about 60 mph (97 kph) when it struck the embankment. A FedEx truck was going about 21 mph (34 kph) when it struck the bus, the report said. The last recorded speed of the UPS truck in which both drivers died was 56 mph (90 kph), according to the board's findings.
Federal investigators said variable speed limit signs may have prevented the crash or lessened its severity.