NTSB Number: SIR-92/04 NTIS Number: PB92-917004SYNOPSIS
These three similar accidents, which resulted in five fatalities. Generated public and Congressional concern about the potential magnitude of the truck-wheel separation problem. To address these concerns, the Safety Board initiated a special investigation in cooperation with the Federal Highway Administration's Office of Motor Carriers (OMC) and the National Highway Traffic Safety Administration (NHTSA) to study the incidence of truck-wheel separations and determine what could be done to correct the problem.
Between November 1991 and February 1992, Safety Board investigators conducted in-depth examinations of the fatal wheel-separation accidents that occurred in fall 1991, and investigators assessed numerous accident and inspection sources in support of this special investigation. Preliminary analysis indicated that most existing databases did not distinguish between wheel-separation and tire-failure accidents. Investigators surveyed the six States that do maintain separate accident data on wheel defects; the Safety Board also interviewed truck carriers, manufacturers, engineers, and mechanics to obtain information for this special' investigation.
Based on its findings, the Safety Board concluded that compared to the 349,000 truck accidents that occur annually, the incidence of wheel separations is small, about 750 to 1,050 per year. From the data accumulated, the Safety Board identified the following maintenance problems:
· Inadequate inspection guidelines, including frequency and procedures
for the proper inspection of wheel fasteners and lubrication of bearings.
· Lack of uniform maintenance guidelines among manufacturers.
· Failure by carriers and mechanics to adhere to recommended
maintenance guidelines published by wheel manufacturers.
As a result of this special investigation, the Safety Board made recommendations to the Department of Transportation, the Federal Highway Administration, the American Trucking Associations, the Motor Vehicle Manufacturers' Association of the United States, Inc., the Society of Automotive Engineers, and the Truck Trailer Manufacturers Association.
RECOMMENDATIONS
As a result of this special investigation, the National Transportation Safety Board made the following recommendations:
to the American Trucking Associations in cooperation with the National Wheel & Rim Association, the Motor Vehicle Manufacturers Association of the United States, Truck Trailer Manufacturers Association, and the Society of Automotive Engineers:
Develop and disseminate model guidelines for the inspection and maintenance of all types of medium/heavy truck wheels. (Class II, Priority Action) (H-92-98)
Develop uniform recommended practices that specify how often truck wheel bearings should be examined. (Class II, Priority Action) (H-92-99)
Promote an educational program on proper wheel tightening procedures through carriers, manufacturers, and government. (Class II, Priority Action) (H -92-100)
Encourage manufacturers to provide a label on trucks that indicates the recommended torque for wheel fasteners, proper tightening sequence, and recommended frequency for retorquing fasteners. (Class II, Priority Action) (H-92-101)
to the Federal Highway Administration, in cooperation with the American Trucking Associations, the National Wheel & Rim Association, the Motor Vehicle Manufacturers Association of the United States, Truck Trailer Manufacturers Association, and the Society of Automotive Engineers:
Support the development of an educational program on proper wheel tightening procedures by the carriers and manufacturers. (Class II, Priority Action) (H-92-102)
to the Department of Transportation:
Encourage the States to separate wheel
defects from tire defects in future accident data collection efforts. (Class
II, Priority Action) (H-92-103)