Edited 28 Nov 2017 22:53, 3 years ago, edited by Transtopic

The London Crossrail can't run DD trains because of the limited loading gauge of the existing Overground network with which it connects, not that they would necessarily choose to if it was possible.  So it's SD.  Crossrail is essentially a century late in linking up separate surface suburban lines through the centre of London, similar to Bradfield's plan for the Sydney Underground.  While Crossrail is automated through central London, it still has a driver for the existing outer sections where it will share some tracks with other Overground services.  It may have metro style rolling stock, but that doesn't make it a "metro" in the accepted sense of the terminology.  It is still basically a "suburban" system similar to Paris's RER and Sydney's rail network.

Unlike London, all of Sydney's suburban lines now traverse the CBD, so there is virtually no need for any further cross city connections.  However, that doesn't mean to say that future track amplification wouldn't be required on existing lines to meet the increased patronage demand for future suburban extensions, such as a link to Badgerys Creek Airport.  The only CBD extensions I would make for the existing network is for an express tunnel from Granville to Barangaroo to augment the Western Line and diversion of the Airport Line from the City Circle to a new terminus (St James perhaps).  All other new inner city lines should be part of a segregated automated metro system.