Adopted: April 14, 1977
TRANSPORT COMPANY OF TEXAS
TRACTOR-SEMITRAILER (TANK) COLLISION
WITH BRIDGE COLUMN AND SUDDEN
DISPERSAL OF ANHYDROUS AMMONIA CARGO
I-610 AT SOUTHWEST FREEWAY,
MAY 11, 1976
NTSB Number: HAR-77/01
NTIS Number: PB-268251
PDF Document (1.47 MB)
About 11:08 a.m., on May 11, 1976, a Transport Company of Texas tractor-semitrailer (tank) transporting 7,509 gallons of anhydrous ammonia struck and penetrated a bridge rail on a ramp connecting I-610 with the Southwest Freeway (U.S. 59) in Houston, Texas. The tractor and trailer left the ramp, struck a support column of an overpass, and fell onto the Southwest Freeway, approximately 15 feet below. The anhydrous ammonia was released from the damaged tank semitrailer.
Six persons died as a result of the accident, 78 persons were hospitalized, and approximately 100 other persons were treated for injuries.
The National Transportation Safety Board determines that the probable cause of this accident was the excessive speed of the vehicle combined with the lateral surge of liquid in the partially loaded tank truck, which caused it to overturn. The cause of 5 of the 6 fatalities and all of the 178 injuries was the inhalation of anhydrous ammonia. Contributing to the severity of the accident was the failure of the bridge rail to contain or redirect the vehicle.