I've heard of two single track sections on the Sydney suburban, since you live there, can you describe them in relation to what you say they should be? Are they any more reliable than the ones in Melbourne? `
SINGLE LINES IN SYDNEY
In Sydney, the Clyde-Carlingford branch is double from Clyde to Rosehill (exclusive). But the double line is all at one end, and not in the middle of the line. An extra loop was proposed, but never built under the Clearways project. Also the round trip running time is a bit more than 30 minutes, so that it is not possible to connect with 30 minute interval trains on the main line. Also, Clyde is a low patronage station with poor connecting, unlike say Granville and Lidcombe. Much better to convert it to light rail, with extra duplication, as part of a Parramatta-Carlingford-Eastwood- Macquarie Uni line.
In Sydney, the Sutherland-Cronulla branch was opened in 1938 as single line, with left hand running loops and island platforms at Gymea and Caringbah. The loops could operate automatically without CTC, though this could lead to "snookers" if two up trains tried to cross two down trains at any loop. Around 1980, Gymea-Caringbah was duplicated with CTC installed. This reduced but did not eliminate delays waiting for 4 per hour trains to clear the single. Generally counter-peak trains were made to wait. Off peak trains at 2 per hour, crossed in the middle of the double line at Miranda. Gymea and Caringbah loops had simultaneous arrivals with intermediate timed train stops, later converted on part duplication to catchpoints.
In Sydney, the Blacktown-Richmond line was single line with loops at
* Quakers Hill (side platforms converted to island with electrification; simultaneous arrivals with timed intermediate trainstops)
* Riverstone (single platform with 2nd side platform later)
* Mulgrave (island platform)
* Windsor (side platform with no platform on loop; short siding used at "loop" ; no longer a crossing place)
* Clarendon (side platform with siding used as "loop"; converted to side platforms after electrification)
When the Blacktown-Riverstone section was electrified, a dock platform was provided for the connecting 2 or 4 car diesel train.
After full electrification, Riverstone, Mulgrave and Clarendon converted to simultaneous arrival with left hand running and catchpoints. NSWR likes catchpoints on running lines.
Duplication occurred first to Marayong (exclusive), extended to Quakers Hill, and further extended to Schofields relocated say 1000m closer to Sydney.
The single line sections on thus line are about the same 7-8 minutes, which allows a 15-minute 4 train per hour in the peak.
In the off peak, a 30-minute service uses every other loop. If a down train is late, it can use the empty loops and run 15 minutes late all the way to the end of the line at Richmond. Before the Clarendon loop was rebuilt, late running down trains had to be terminated in the middle of nowhere at Mulgrave. A letterwriter to the local paper could not see the value of the new loop at Clarendon, which is also in the middle of nowhere, and thought that the $6m cost was a complete waste of money. Such is the public's understanding of railway timetables. The loops at Clarendon and Mulgrave are timetabled once a day to clean the rails; they are mainly there for special extra trains and for late running.
On Richmond Air Base show days, (near Clarendon), the single line between Clarendon and Richmond is used to stable trains. Replacement buses are provided Clarendon to Richmond.