The recording is also used where platforms are non-standard height. Deep-level tube trains have a floor height around less than sub-surface stock trains. Where trains share platforms, for example some Piccadilly line (deep-tube) and District line (sub-surface) stations, the platform is a compromise. On London's Metropolitan line, a gap has been created between the train and the platform edge at Aldgate and Baker Street stations. This is due to the phasing out of the old "A" stock trains and their replacement with "S" stock trains, which have low floors to ease accessibility for disabled people.