Most crashes never have just one cause, but in the case of the fatal 2020 Southern California bus crash, the state of the tires played a significant role.
As a result of the findings of its investigation, the National Transportation Safety Board (NTSB) is working with the United Motorcoach Association (UMA) to explain to motorcoach carriers how to avoid similar situations.
“To ensure industry awareness of this crash investigation and its findings, we recommended that the American Bus Association and the United Motorcoach Association inform their members about the circumstances of this crash and encourage them to create a policy on speed and safe driving on wet roadways and under inclement weather conditions based on authoritative guidance,” the NTSB said in a statement. “We also recommended that these two associations encourage their members to adopt the recommended tire rotation practices established by the U.S. Tire Manufacturers Association, and inform their members who operate in California of the requirements about pre-trip briefings and/or signage in buses concerning California’ mandatory seat belt use law.”
NTSB Investigator Michael LaPonte recently joined a UMA Town Hall to explain the final investigation report on the 2020 Palo Mesa, California, crash, and the lessons learned.
“What we focused on were four areas, basically, in this crash: the speed of the vehicle, the roadway, the tire conditions and the driver’s response to the crash sequence when he actually started losing control,” LaPonte said during the Town Hall presentation. “A very significant issue was the tire tread condition on the bus.”
NTSB findings
The agency’s final report noted several issues regarding the tires:
- The company used new tires only on the front axle.
- It would move both front tires to the rear axle at 5/32-inch tread depth.
- The company would remove rear tires from service at 2/32-inch tread depth.
- The rear tires on the crash bus had been replaced twice since November 3, 2019.
While some motor carriers follow the same tire rotation practices, they aren’t recommended by the UMA Safety Council or the U.S. Tire Manufacturers Association.
During the recent Town Hall session, LaPonte reviewed insights from the NTBS investigation to help bus and motorcoach owners, management and safety personnel avoid similar situations. He has more than 40 years of experience in the motor carrier industry, working every job from dock worker and driver to terminal manager. He worked for the Federal Motor Carrier Safety Administration as a safety investigator prior to joining the NTSB in 2015.
Overall, the investigation concluded that inappropriate driver responses exacerbated the situation to a complete loss of control, during which the bus left the roadway to the right and rolled over. During the rollover, the integrity of the bus’ roof was compromised, so that the roof partially collapsed, and many windows were broken out, putting occupants’ safety at risk. Additionally, most of the 20 passengers were not wearing the available lap/shoulder belts, which further increased passengers’ risk of ejection and displacement.
The crash, which occurred at 10:23 a.m. on Feb. 22, 2020, caused the death of three of the 20 passengers on board, and seriously injured another 12. The 30-passenger bus traveling in the left southbound lanes of Interstate 15, departed the roadway, rolled and came to rest on its roof.
Rainfall a factor
Operated by Executive Lines, the bus was making a daily run from the Los Angeles Basin area to San Ysidro, California, where passengers could easily cross the border into Mexico.
The tire situation was exacerbated by moderate rainfall that left the roadway wet.
While completing the crossing of the bridge over the San Luis Rey River in San Diego County, the 52-year-old driver lost control of the bus. In response, he “overcorrected and braked,” according to LaPonte.
“He was going about 74 mph, and the speed limit is 70, which was too fast for the wet roadway conditions,” said LaPonte.
He said the vehicle went into a sideways skid and tripped on the curbing on the shoulder, rolled and ended up on its roof partially down the bank.
The investigation showed the minibus rolled over one-and-a-half times (540 degrees) and slid about 16 feet down the embankment of a 95-foot-wide clear zone. The bus came to rest on its roof, 118 feet west of the white edge line of the roadway and 306 feet south of the end of the bridge deck. The vehicle’s roof was severely deformed, knocking out several windows, which allowed five passengers on the bus to be ejected. Three of them died.
“The sad part of this is that this bus was equipped with three-point lap and shoulder belts, and there were only two individuals on the bus wearing them,” LaPonte said. “Both of them were wearing them incorrectly. They were only using the lap portion of the belt. So, actually, one of the persons who was belted incorrectly was ejected. Fortunately, they were not fatally injured.”
Further findings
He said the bus was transporting passengers despite having two tires with unacceptably low tread depths, which can reduce a vehicle’s traction on the road. The wet roadway further reduced the available traction. According to the report, the bus was also traveling at an excessive speed for the roadway conditions, given the suboptimal condition of the bus’ tires, which would have made it more difficult to recover from a loss-of-control event.
The NTSB determined the probable cause of the crash was:
- The loss of vehicle control, due to the combination of the low substandard tread depth of the rear axle tires.
- The excessive speed for the wet roadway and vehicle conditions.
- The driver’s inappropriate inputs before and during the loss-of-control event.
The NTSB further determined that contributing factors in the crash included:
- Executive Lines’ inadequate vehicle inspection process, which permitted the bus to operate in passenger service despite having two tires with treads below the minimum required depth.
- Contributing to the severity of the injuries was the National Highway Traffic Safety Administration’s failure to require roof strength standards for buses.
- Executive Lines’ failure to follow California’s requirement to inform passengers about the state’s mandatory seat belt use law.
- Passengers’ limited use of the available lap/shoulder belts.
“To ensure industry awareness of this crash investigation and its findings, we recommended that the American Bus Association and the United Motorcoach Association inform their members about the circumstances of this crash and encourage them to create a policy on speed and safe driving on wet roadways and under inclement weather conditions based on authoritative guidance. We also recommended that these two associations encourage their members to adopt the recommended tire rotation practices established by the U.S. Tire Manufacturers Association, and inform their members who operate in California of the requirements about pretrip briefings and/or signage in buses concerning California’ mandatory seat belt use law,” according to an NTSB statement.
The full Town Hall presentation can be viewed by UMA members here.
