There’s a little-used alternative to through-running as described in TFA, which is to turn trains around in an underground loop in the city centre and send them out again, usually on the same line they came from. This is done in Sydney (1920s) and Melbourne (1970s).
In the case of Melbourne, the design was chosen because of the extremely lop-sided development of the city, whose centre (“the city”) lies at the head of a bay, with most of the population and population growth to the south and east of the city in the 1970s. This is true to a lesser extent in Sydney, bearing in mind that its city loop was designed before the Harbour Bridge was built.
Melbourne’s current through-running project, the Metro Tunnel, appears in the first table, but it doesn’t belong in the second table of cities which could greatly benefit from future through-running projects. All 16 lines can access the city loop (which has 4 parallel tunnels). Due to capacity constraints, most of the time one of those 16 lines terminates at a main city station, and two others through run with each other. The Metro Tunnel will relieve the city loop, similar to the Munich trunk amplification project described in TFA; once it opens all lines will either through-run or go around a loop.
Locals are used to the City Loop but some visitors find it hard to navigate. Each line runs either clockwise or anticlockwise. For historical reasons two of the four loops still reverse direction in the middle of the day.
It’s true that a further through-running tunnel (Metro Tunnel 2) and conversion of two of the four City Loop tunnels to through-running (City Loop Reconfiguration) appeared on the long-range plans from 2012. But these are not required yet; the city is building three other major rail projects first.