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Accident Report Detail

Transport Company of Texas, Tractor Semitrailer (Tank) Collision with Bridge Column and Sudden Dispersal of Anhydrous Ammonia Cargo

Executive Summary

‚ÄčAbout 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.

Probable Cause

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.‚Äč

Accident Location: Houston , TX    
Accident Date: 5/11/1976
Accident ID: DCA76H050

Date Adopted: 4/14/1977
NTSB Number: HAR-77-01
NTIS Number: PB-268251

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