Highway Accident Report : bus climbing of bridge rail and overturn near Martinez, California, May 21, 1976 : Student Transportation Lines, Inc., charter.

At 10:55 a.m. on May 21, 1976, a charter bus, carrying 52 persons struck and mounted a section of the bridge rail system on the Marina Vista offramp of I-680 near Martinez, California. The bus rolled off the top of the curved bridge rail and landed on its roof. Twenty-nine of the occupants died and the rest sustained injuries ranging from minor to serious. The National Transportation Safety Board determines that the probable cause of this accident was the failure of the driver, who was unfamiliar with the bus, to correctly monitor the service brake air pressure gauge, recognize the loss of air, and take appropriate action including application of the emergency airbrake. Contributing to the accident were: (1) the failure of the air compressor drivebelt, (2) the failure of the maintenance program and pretrip inspection to detect and replace the deteriorated air compressor drivebelt, (3) the failure of the signing system to adequately alert the driver to the critical geometrics of the ramp, (4) the severe radius of the curvature of the ramp, (5) the design of the curb as part of the ramp railing, and (6) a bridge rail system that did not redirect the bus.