Seat Belts

Belt webbing strengths are dictated in Federal Motor Vehicle Safety Standard 209. Lap-only belts must have at least 6,000 pounds of tensile strength. For lap-torso belt systems, the pelvic webbing must withstand a 5,000-pound pull and the upper-torso webbing tensile strength must be at least 4,000 pounds.

Most automobile manufacturers specify 6,000-pound webbing material so that they can use it in any belt system.

Occasionally, an accident investigator will need to determine the difference between safety belt webbing that either has been cut by rescue personnel or has failed due to tension overload. Fibers at the end of a cut belt will be relatively uniform, while the ends of an overloaded belt will be stringy and stretched, producing a horsetail-like appearance.