of these units have since had the centre car transferred to different units of the class, whilst another eight have been upgraded and redesignated as the Class 159. The final ten units were built specifically for West Yorkshire PTE Metro services around Leeds. The majority of units, as originally built by British Rail Engineering Limited (BREL), were configured with standard-class accommodation only; a number of Scottish-based sets were fitted with a small first-class section in one vehicle. Later on, several other sets were retrofitted with first-class accommodation. The passenger saloons are air-conditioned, which was a first for regional trains in the UK. Passenger facilities and performance Around the time of its introduction, British Rail was keen to promote the qualities of the Class 158, on one occasion publicly describing it as having brought "new standards of comfort and quality to rail travel on Regional Railways' key long-distance cross-country routes". As originally built, the interiors were fully carpeted throughout, large "panoramic" windows lined the sides, and a variety of seating arrangements were present, including airline-style and bays of four set around tables. Unlike the previous members of the Sprinter family, such as the Class 156 SuperSprinter, the Class 158 was outfitted with air conditioning units, an on-board payphone, power-operated interior doors, a toilet in each carriage, and provision for a refreshment trolley service. Despite an increased top speed of , the Class 158 reportedly promised a smoother and quieter ride in comparison to its predecessors. Toilets were fitted to both vehicles; one was wheelchair-accessible (as defined at the time of construction) and one standard. A wheelchair space was provided in the passenger section closest to the accessible toilet. Luggage racks were fitted at each end of the saloon, one of which is capable of being locked for mail and parcels. In terms of serviceability, the Class 158 was anticipated to achieve of operation between major services, and to have a range of up to from each refuelling. Technical problems Despite the attention given to its passenger facilities, the construction and engineering technology used on the Class 158s contributed to some issues during its service life. As a lightweight unit and the first members of the Sprinter family to use disc brakes, autumn leaf mulch built up on wheel rims and prevented the units from correctly operating signalling track circuits. Though this was later solved by installing scrubbing blocks to clean the