London–Aylesbury line Aylesbury and by platform extensions up to Stoke Mandeville. In 1961 LT withdrew the Metropolitan line from Aylesbury and since then it goes only as far as Amersham. Following the end of steam-hauled Metropolitan line trains in 1961 the service was provided by British Rail Class 115 diesel multiple units until 1992 (which were then replaced by the line's current rolling stock) - along with Metropolitan line electric multiple units south of Amersham. Responsibility for the line north of Amersham was transferred from London Transport to British Railways on 11 September 1961; London Underground signage at the stations on this
Medium-capacity rail system requisite ridership due to network inadequacies (e.g. single-tracking) or changing demographics. In contrast with most light rail systems, an MCS usually (though not always) runs on a fully grade separated exclusive right-of-way. In some cases, the distance between stations is much longer than typically found on heavy rail networks. An MCS may also be suitable for branch line connections to another mode of a heavy-capacity transportation system, such as an airport or a main route of a metro network. The definition of a medium-capacity system varies due to its non-standardization. Inconsistencies in international definitions are even reflected within individual countries.