Which of these damages to the safety belts indicates an absolute need to replace the belt with a new one?

In the photo you can see the webbing of a seat belt and a seat belt buckle on the rear seat. Abrasions, narrowed sections and tears in the belt webbing mean that the belts must be replaced with new ones - answer B. A twisted or rolled-up belt (A) only needs to be untangled, and permanent dirt and stains (C) are a cosmetic defect - dirty webbing still has all its fibres intact and holds just as well.

The Regulation on the technical conditions of vehicles requires a passenger car to be fitted with seat belts on seats that have anchorage points, and the Road Traffic Act requires the driver and passengers to use them while driving. The belt webbing is woven from fibres that, during a collision, carry forces measured in tonnes - every abrasion, narrowing or tear means that some fibres are already broken and the belt may snap exactly when it is supposed to save a life. Belts must also be replaced after every serious accident, even if they look fine, because the pyrotechnic pretensioners have fired and the webbing has been stretched. During a check before driving you pull the belt out to its full length and check that there is no damage and that it rolls back freely.

Legal basis: § 11 para. 1 point 8 of the Regulation on the technical conditions of vehicles and the scope of their necessary equipment; Art. 39 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)