This British Standard specifies requirements for the assembly of powered and non-powered wheelsets with inboard bearings comprising elements conforming to the following standards. BS 8535 for axle design. BS EN 13261 or BS 5892-1 for axles. BS EN 13262 or BS 5892-3 for wheels. NOTE Some characteristics are specified as a function of Category 1 or of Category 2. Category 1 is applicable for wheelsets whose operating speed is to exceed 200 km/h. Category 2 is applicable for wheelsets whose operating speed is not to exceed 200 km/h, and comprises two sub-categories: Category 2a is applicable when the operating speed is to be up to and including 120 km/h; Category 2b is applicable when the operating speed is to exceed 120 km/h, but is not to exceed 200 km/h.