wheels, temporary solutions were sought during October 1992, with some units split and formed into hybrid units with Class 156 coaches, the latter possessing tread brakes which cleaned the wheels as a by-product of their standard operation. The air conditioning systems of the Class 158 was also proved to be unreliable in service, particularly following the outlawing of the CFC gases with which they has been originally designed to work. In the privatisation era, many operators elected either to re-engineer or entirely replace such equipment. As a result, the systems in use and their effectiveness vary considerably across the fleet. The lightweight aluminium body of the Class 158 leads to a good 'route availability' score, meaning that it is able to operate in areas of Britain's railways that heavier units cannot. However, the units were refused permission by Network Rail to operate on the Conwy Valley and Borderlands lines due to station dwell times and issues of platform clearance. Operations British Rail ScotRail was the first part of British Rail to introduce the Class 158s to public service in September 1990. These were employed on to services, as well as services to and . The Class 158s then went on to be deployed elsewhere in Britain, primarily in the Midlands, Northern England, Wales and the South West. The majority of the Class 158 fleet was directed towards the Regional Railways division; accordingly, it rapidly become the dominant platform on the numerous secondary express services between provincial towns and cities across Great Britain. Examples include the long-distance TransPennine services in the north of England, as well as a range of upgraded regional services in the Midlands, Wales and the South West. During the mid-1990s, the Alphaline brand centered around the Class 158s and the higher-end regional express services. These were routinely promoted as possessing premium passenger amenities that traditional regional rolling stock had lacked, such as the presence of British Telecom card phones and air conditioning. A small batch of units, numbered 158747-158751, were used by the InterCity division to supplement its core fleet on a number of cross-country services, mainly from the North West to Scotland, but also to Portsmouth. At one point, Class 158s regularly appeared on Sunday mornings between Birmingham and Doncaster. Post privatisation After the privatisation of British Rail, the Class 158 fleet was divided among several franchises. ScotRail The first privatised incarnation of ScotRail inherited a