SIR-92-1

SPECIAL INVESTIGATION REPORT
Adopted: February 4, 1992
CARGO TANK ROLLOVER PROTECTION

NTSB Number: SIR-92/01
NTIS Number: PB92-917002

SYNOPSIS
Between January and May 1991, the National Transportation Safety Board investigated seven highway accidents in which cargo tanks overturned and hazardous materials were released through damaged closures or fittings on top of the tanks; none of the cargo tank shells had been breached. The cargo tanks involved in these accidents were U.S. Department of Transportation (DOT) specification MC 306 or MC 312 bulk liquid cargo tanks. Under DOT regulations contained in Title 49, Code of Federal Regulations, Part 178, all of the tanks examined during the investigation were required to have rollover protection for the fittings on the top of the tanks. All of the tanks were also equipped with rails or guards to provide that protection. Because of the damage to the top fittings in these accidents, the Safety Board has, in this report, examined the adequacy of the design and the performance of the rollover protection devices installed on the tanks.

During the course of this special investigation, the Safety Board also assessed the adequacy of the DOT regulations for rollover protection as promulgated by the Research and Special Programs Administration (RSPA) and the effectiveness of the Federal Highway Administration (FHWA) to enforce regulations pertaining to the design and construction of cargo tanks. The Safety Board also reviewed the adequacy of the accident data collected by the FHWA and the RSPA to detect the frequency of rollover accidents and to identify potential problems related to the design and construction of bulk liquid cargo tanks.

The safety issues discussed in this report are:

1. The adequacy of DOT regulations regarding the design and performance of rollover protection devices installed on bulk liquid cargo tanks;

2. The effectiveness of FHWA's oversight pertaining to the design and construction of bulk liquid cargo tanks; and

3. The adequacy of accident reporting to and data collected by the DOT.

Safety recommendations addressing these issues were made to the Research and Special Programs Administration, and the Federal Highway Administration.

RECOMMENDATIONS

As a result of this special investigation, the National Transportation Safety Board made the following recommendations:

--to the Research and Special Program Administration, U.S. Department of Transportation:

Provide cargo tank manufacturers with specific written guidance about (a) the factors and assumptions that must be considered when calculating the loads on cargo tank rollover protection devices in determining compliance with existing Department of Transportation performance standards; and (b) acceptable means to shield and protect the top-mounted closure fittings on all bulk liquid cargo tanks. (Class II, Priority Action) (H-92-1)

Assist the Federal Highway Administration to evaluate the design of the rollover protection devices installed on all cargo tanks manufactured by the Acro Trailer Company and by New Progress, Incorporated, to determine if the cargo tanks comply with existing Department of Transportation standards. (Class II, Priority Action) (H-92-2)

Assist the Federal Highway Administration to improve the performance of the rollover protection devices on bulk liquid cargo tanks by:

Modeling and analyzing the forces that can act upon rollover protection devices during a rollover accident. (Class III, Longer Term Action) (H-92-3)

Promulgating performance standards for rollover protection devices that are based on the engineering modeling and analysis conducted in response to Safety Recommendation H-92-3. (Class III, Longer Term Action) (H-92-4)

Phasing out from hazardous materials service the use of all cargo tanks that fail to meet the new performance standards promulgated in response to Safety Recommendation H-92-4. (Class III, Longer Term Action) (H-92-5)

Implement, in cooperation with the Federal Highway Administration, a program to collect information necessary to identify patterns of cargo tank equipment failures, including the reporting of all accidents involving a Department of Transportation specification cargo tank. (Class III, Longer Term Action) (H-92-6)

--to the Federal Highway Administration, U.S. Department of Transportation:

Evaluate, with the assistance of the Research and Special Programs Administration, designs of rollover protection devices installed on all cargo tanks manufactured by the Acro Trailer Company and by New Progress, Incorporated, to determine if the cargo tanks comply with existing Department of Transportation (DOT) standards; and then require that cargo tanks failing to comply with existing DOT standards be removed from hazardous materials service or be modified to comply with the standards. (Class II, Priority Action) (H-92-7)

Implement a program, including the acquisition of the necessary technical resources, to evaluate the design and construction of cargo tanks for compliance with Department of Transportation specifications. (Class II, Priority Action) (H-92-8)

Implement, in cooperation with the Research and Special Programs Administration, a program to collect information necessary to identify patterns of cargo tank equipment failures, including the reporting of-all accidents involving a Department of Transportation specification cargo tank. (Class III, Longer Term Action) (H-92-9)

Improve, with the assistance of the Research and Special Programs Administration, the performance of the rollover protection devices on bulk liquid cargo tanks by:
Modeling and analyzing the forces that can act upon rollover protection devices during a rollover accident. (Class III, Longer Term Action) (H-92-10)

Phasing out from hazardous materials service the use of all cargo tanks that fail to meet the new performance standards promulgated in response to Safety Recommendation H-92-11. (Class III, Longer Term Action) (H-92-12)