Interpretation ID: nht93-7.47

DATE: November 3, 1993

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: The Honorable Phil Gramm -- United States Senate

TITLE: None

ATTACHMT: Attached to Privacy Form dated 9/19/93 from Thomas J. Devon to Senator Phil Gram (OCC number illegible)

TEXT:

Thank you for your inquiry on behalf of your constituent, Mr. Thomas J. Devon of Longview, Texas. The Federal Highway Administration (FHWA) referred your inquiry to this office, since the National Highway Traffic Safety Administration (NHTSA) administers Federal safety standards for tires.

In his communication with you, Mr. Devon expressed concern about separated treads from retreaded large truck tires. He "referred to the deaths of two young women reportedly caused when they lost control of their vehicle after striking a separated tread in the road. Mr. Devon is concerned that retreaded tires do not meet the same standards as new tires and requested data on accidents caused by separated tire tread sections on the roadway.

By way of background information, the National Traffic and Motor Vehicle Safety Act of 1966, 15 U.S.C. S1381, et seq. (Safety Act) authorizes NHTSA to issue safety standards applicable to new motor vehicles and new items of motor vehicle equipment. Pursuant to that authority, NHTSA has issued various Federal Motor Vehicle Safety Standards (FMVSS) applicable to tires: FMVSS Nos. 109 and 110 for new pneumatic passenger car tires; FMVSS Nos. 119 and 120 for new pneumatic tires for other than passenger cars; and FMVSS No. 117 for retreaded passenger car tires. There is currently no standard applicable to retreaded tires for vehicles other than passenger cars. This is because the agency is not aware of any data suggesting a safety need for such a standard.

With respect to tire tread separation, examination of actual tire scraps from the nation's highways have indicated that about 60 percent came from retreaded tires and 40 percent from original tires. Because of the many complaints about heavy truck tire tread scraps on and around the highways, the University of Michigan conducted a study in the mid-1980s' entitled "Large Truck Accidents Involving Tire Failure." That study concluded that most large truck tire failures are caused by vehicle overload and/or tire underinflation. Underinflation causes excessive flexing of the tire. The friction resulting from that flexing causes excessive heat buildup which can, in turn, result in tread separation or other tire failure. Indeed, the heat buildup has been known to be so extreme as to cause the tire to burst into flame.

The findings from the Michigan study led the FHWA to prohibit the operation of commercial motor vehicles with overloaded and underinflated tires, unless the vehicle is operated pursuant to a special permit issued by a state. That permit, however, requires a reduced speed to compensate for the increased tire loading. In addition, the vehicle and the tires must be maintained in a safe operating condition at all times. FHWA conducts

roadside inspection programs to ensure that such requirements are being met.

While scraps of tires on the roadway could pose a safety hazard to motorists, this agency has no real world crash data to indicate what percentage of motor vehicle crashes could be attributed to separated tire treads. Our crash data are limited to the general category of tire failure.

Please be assured that NHTSA and FHWA, as well as the tire industry itself, are engaged in ongoing efforts to alleviate this problem by appropriate publicity to large truck owners and operators regarding proper tire care and maintenance and by vigorous vehicle inspection programs.

I hope this information is helpful. If your constituent has any further questions, he may contact Walter Myers of this office at this address or at (202) 366-2992.