I want to start a new scenario based on UK.
Cities are placed by Public Player on the right locations and if possible with the right size.
However London is a problem. ~ 5 million inhabitants !!
Is there a max size for cities? What seems a reasonable size for simulating London?
In what era is this? London now has closer to 7 million inhabitants, but many years ago the population was much smaller. Bear in mind also that current release versions of Experimental do not have realistic ratios between reported population numbers and actual town size.
In his Great Britain rail simulation, Carl handles the issue by dividing London into its 32 local authorities. After all, traffic from Stratford to Wimbledon is just as much regional traffic as that from Wigan to Liverpool.
If 32 cities seems a bit too much, you could use the names of the main authorities in the early 20th centuries
London
Westminster
Croydon (south of the river)
East and West Ham (= northeast)
Middlesex (= northwest suburbs)