From N Gauge wiki
The London Underground (colloquially "The Tube") is a wholly owned subsidiary of Transport for London (TfL). It comprises 11 lines running across London and outwards to the suburbs, particularly in the North of the city. The lines are divided into two groups, namely the sub-surface lines which were built by cut-and-cover techniques and the deep tube lines which were built by tunnel boring. The sub-surface lines are inter-connected while the deep tube lines are mostly separate entities.
The lines are:
- Bakerloo Line - deep tube, brown
- Central Line - deep tube, red
- Circle Line - sub-surface, yellow
- District Line - sub-surface, green
- Hammersmith and City Line - sub-surface, pink
- Jubilee Line - deep tube, grey
- Metropolitan Line - sub-surface, purple
- Northern Line - deep tube, black
- Piccadilly Line - deep tube, blue
- Victoria Line - deep tube, light blue
- Waterloo and City Line - deep tube, turquoise
The East London line was part of the Underground until 2007. It reopened in 2010 as part of the Overground, which as a whole inherited orange as its signature colour.
The stock used on the lines varies significantly from line to line. Sub-surface lines use trains with similar dimensions to those on the National Rail network and are classified by letters, e.g. Type S stock which is being introduced to many of the lines. The deep tube lines use much smaller trains which are classified by year of introduction.