At the start of the 1990s, the reliability of the fleet became a problem again. By this time, the class was solely used on the West of England route, having been replaced on the Oxford route by Class 47/4 locomotives, displaced from Railfreight Distribution after the collapse of Speedlink in 1991. Arguably, the Class 50s were not suitable for the stop-start service pattern of Waterloo-Exeter services, nor to the extended single-line sections of this route, where a single locomotive failure could cause chaos. Therefore, the decision was taken to retire the fleet, temporarily replacing them with Class 47/7 locomotives, which were in turn replaced by new diesel multiple units. From 1992, the Oxford route was worked by Class 165 and Class 166 units, whilst Class 159 units were introduced onto the West of England route in 1993.