Greyhound bus collision with concrete overpass support column on I-880, San Juan Overpass, Sacramento, California, November 3, 1973.

A Greyhound bus off the road and hit a concrete overpass support column. The probable cause was driver incapacitation. Contributing to the fatalities and injuries were (1) the failure of the guardrail to direct the bus away from the bridge column;(2) the velocity of the bus; and (3) the structural failure of the seats in areas of the where crash forces were moderate