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Accident Report Detail

Cargo Tank Overturn on the Capital Beltway, 1-95

Executive Summary

​About 12:40 p.m., e.d.t on September 6, 1985, a 1902 GMC 2-axle truck fitted with a 1973 MC-331 cargo tank overturned while traveling southbound on the Capital Beltway, I-95, near Largo, Maryland. The 2,500-gallon capacity cargo tank contained about 1,375 gallons of propane. The Poist Gas Company truck was traveling between 50 and 55 mph when, according to the drivers the steering wheel started shaking violently and "flew out of my hands." The driver stated that he took his foot off the accelerator but did not brake because be believed that one of the vehicie's tires was experiencing a blow out. The truck veered across the right paved shoulder of the highway and onto a grass shoulder. It then traveled 300 feet down the grass shoulder until the driver steered the truck back to the left to avoid hitting a tree. The truck slipped the north end of a guardrail when it reentered the paved shoulder of the highway as the driver tried to regain control of the truck. The truck then traveled 510 feet down the paved shoulder and the right travel lane of the highway before rotating clockwise about 80° and overturning on Its left side. The vehicle continued to rotate another 100° as it slid 400 feet down the highway on Its left side. The truck came to rest facing north (180° opposite its original direction of. travel) with the top of the cargo tank parallel with and against the guardrail At the time of the accident the roadway was dry and the weather was clear.

Probable Cause

The National Transportation Safety Board determines that the probable cause of the accident was the circumferential tread separation of the left front tire, which caused the driver to lose steering control of the vehicle. Contributing to the accident was the continued use of unbalanced out of round tires on the steering axle of the vehicle which produced wheel vibration. Contributing to the severity of the accident was the release of propane from the eargo tank through a break in the discharge line, and the failure of safety valves on the cargo tank to prevent the continuous flow of propane from the cargo tank after the accident.

Accident Location: Largo , MD    
Accident Date: 9/6/1985
Accident ID: DCA85HZ008

Date Adopted: 6/30/1987
NTSB Number: HAR-87-02-S
NTIS Number: PB87-916204

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