In message , John Rowland
writes

In 2000 or so, track utilisation on the Windsor lines was very low (peak
service of 6tph on each of the 4 tracks between Barnes and Waterloo, IIRC)
and I don't think much has changed since.

A rather significant change occurred in late 2004: the up lines (but not
the down lines) were swapped, giving the following pattern (from north
to south)

up slow
up fast
down slow
down fast

This would mean that down services to Wimbledon via East Putney would
have to share the Windsor line, but up services (if the Putney flyover
was to be reinstated) would have to share the slow line.

Probably still not impossible, but it would involve some complex
timetabling - especially since timings of both Windsor and stopping
services are already heavily constrained by the four level crossings on
the two-track part of the line between Barnes and Richmond.
--
Paul Terry