On this day, May 21, 1976, the bus crash that became the NTSB's deadliest highway disaster investigation ever occurred.

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Yuba City bus disaster

Tools
Coordinates: 38.0244°N 122.1110°W

Details
Date: May 21, 1976; 10:55 AM
Operator: Student Transportation Lines, Inc
Cause: Brake failure due to insufficient maintenance, driver training, driver proficiency
Statistics
Passengers: 53
Deaths: 29
Injured: 4

The Yuba City bus disaster occurred on May 21, 1976, in Martinez, California. A chartered school bus transporting 52 passengers on an elevated offramp left the roadway, landing on its roof. Of the 52 passengers (not including the driver), 28 students and an adult adviser were killed in the crash.

It remains the deadliest highway disaster ever investigated by the National Transportation Safety Board (NTSB) since its creation.

Incident

On May 21, 1976, Yuba City High School chartered a school bus from Student Transportation Lines, Inc. to transport its a cappella choir from Yuba City, California, to Miramonte High School in Orinda for a friendship day involving the choirs of the two schools. The company supplied a Crown bus, dating from 1950.

The accident occurred at 10:55 a.m., as the driver, Evan Prothero, 49, of Olivehurst, took the Marina Vista Avenue off-ramp (exit 56) from I-680 southbound from the Benicia–Martinez Bridge. Prothero was unfamiliar with this bus, and mistook the low air pressure warning (for the air brakes) for a warning of low engine oil pressure. Intending to stop for oil, the driver exited the freeway at the aforementioned off ramp; the air brake system failed due to lack of air pressure. With no braking capability, the bus struck the mounted bridge rail and left the elevated roadway. After falling 21.6 feet (6.6 meters), the bus landed on its roof, crushing it to the base of the window line.

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