What is Deep-level tube lines?
{{no sources|date=December 2013}} {{tone|date=December 2013}} '''Deep-level tube lines''' were built by [[tunnelling shields]] and are tunnels that are deep underground that allow trains to run through them. They are commonly found on the [[London Underground]]. An example is the [[Victoria line]].<ref>{{Cite web|url=http://www.independent.co.uk/life-style/history/150-facts-for-150-years-of-the-london-tube-8444153.html|title=150 facts for 150 years of the London Tube|date=2013-01-09|website=The Independent|language=en|access-date=2020-07-13}}</ref> The depth creates ventilation problems. Powerful fans must push clean air very far underground. In the event of an emergency the people trapped on-board cannot get off due to the insufficient space inside the tunnel compared to the subsurface line. == References == <references /> [[Category:London Underground]] {{transport-stub}}