A tale of two metros: how the London tube beat the New York subway | Underground cities | The Guardian
Britain's Other Underground Train, Tube, Metro Rail Systems, and Networks - Anglotopia.net
Bristol could get underground railway to beat road congestion
UK Transport System and How It Compares With the USA - WanderWisdom
Revealed: London's secret underground railway system - CNN Style
This is why Reading and four other Berkshire towns are on the London tube map - Berkshire Live
London Underground | subway, London, England, United Kingdom | Britannica
Britain's Other Underground Train, Tube, Metro Rail Systems, and Networks - Anglotopia.net
London Underground: The UK cities with an underground Tube system you might not know about - MyLondon
How many cities have underground in UK? - Quora
End London-centric approach and invest £140bn in 11 underground systems, Scape say | Infrastructure Intelligence
British trains 'up to four times slower outside the south-east' | Rail transport | The Guardian
Which UK cities outside London have subway/metro/underground/tube systems? - Quora
Why is London the only city with a subway system in the UK? - Quora
London Underground: The UK cities with an underground Tube system you might not know about - MyLondon
The World's Oldest Metro Systems - WorldAtlas
Going underground: the cheapest, deepest, oldest subway systems in the world – but which is home to its own mosquito? | South China Morning Post
World's oldest metro systems - Railway Technology
The power of urban rail - Arup
Does any Indian city has underground metro rail system? If not, why? - Quora
London Underground: The UK cities with an underground Tube system you might not know about - MyLondon
How many cities have underground in UK? - Quora
List of metro systems - Wikipedia
Subway systems by the numbers - BBC Travel
