The NSW government has a history of duplicating the Richmond piece by piece. The first piece was a duplication through to Quakers Hill. This has allowed additional trains to run between Quakers Hill and Blacktown. So whereas the rest of the line through to Richmond is limited to a frequency of 2 trains per hour (TPH), Quakers Hill manages 6TPH during an hour in the morning peak and 4TPH during an hour in the evening peak.
Plans are currently in place to duplicate the line through to Vineyard. This will result in the 4 stations in proximity to the Northwest Growth Centre (NWGC) – Quakers Hill, Schofields, Riverstone and Vineyard – having a complete track pair running through them. There are an additional 70,000 dwellings planned for the NWGC over the next 25-30 years, which will see an additional 200,000 people reside in the area. Duplication of the Richmond Line is one strategy the government has to provide additional transport infrastructure for the area (as clearly a single track of heavy rail will be insufficient).
Interestingly, the Northwest Rail Link as currently planned only barely penetrates the NWGC (see map). However there is significant scope in place to extend it through to Schofields Station, Marsden Park and then the Western Line, probably at Mount Druitt, thus linking it up with both the Richmond and Western Lines. This remains idle speculation at this point, and is little more than a “long term corridor” to be considered post-2040.