SPRINGFIELD, Ill. (AP) — Overnight parking for long-haul truckers at interstate rest stops is critically short and was a key contributor to a 2023 Greyhound bus crash in Illinois that killed three people, federal regulators said Tuesday.

The National Transportation Safety Board said driver fatigue and poor company oversight of its drivers also played key roles when the Greyhound bus exited Interstate 70 onto a rest area ramp east of St. Louis and struck three semitrailers parked on the shoulder.

Board Chairperson Jennifer Homendy said the crash, which sheared off the right side of the bus and injured 12 aboard, was preventable.

“Our investigation brought to light a critical shortage of safe truck parking and made clear a painful lesson: Until we address this important safety issue, lives are at risk on our nation’s roads,” she said.

Truck parking on rest stop entrance and exit ramps is illegal, but the ban is seldom enforced because there’s insufficient parking for the 13 million rigs on the nation’s roads and the federal government electronically monitors truckers’ hours on the road and their rest periods.

The board, meeting in Washington, also cited ​​the bus driver’s fatigue and “deficient driver oversight by Greyhound,” including the company’s failure to address the driver’s “recurring unsafe driving behaviors.” Records compiled during the investigation showed the driver had been involved in four prior accidents, two of which were deemed preventable, and an electronic monitor caught him driving over the speed limit on repeated occasions.

A spokesman said via email that “Greyhound Lines has fully cooperated with the NTSB since the beginning of this investigation” but declined further comment, citing ongoing litigation.

The westbound bus, with 22 passengers, entered the rest area near Highland, 32 miles (about 51 kilometers) east of St. Louis at 1:48 a.m. on July 12, 2023. It slid along the sides of three trucks parked for the night.

None of the truck drivers was hurt, but three bus passengers were killed and the bus driver and 11 other passengers were injured.

The report also noted that injuries could have been minimized if more passengers had been wearing safety belts provided. The National Highway Traffic Safety Administration adopted a rule in 2019 requiring commercial buses to have seatbelts for the driver and every passenger. Illinois law requires the use of seatbelts.