T9 Northern line

The T9 Northern Line is a railway line that runs between Hornsby and Gordon. It is identified by the code.

History
This line has undergone many changes over the past twenty years. It was originally known as the Main North Line (after the physical rail line that it runs on) and had a route of Cowan ↔ Hornsby ↔ Epping ↔ Strathfield ↔ City ↔ North Sydney. It was assigned the colour red.

Due to the branding change when CityRail was introduced, the colour was changed slightly and the line was renamed to the Northern Line. At the same time, the limit of suburban services was cut back to Berowra and Cowan became an intercity station, no longer served by Northern Line services.

The Epping to Chatswood Rail Link was opened in 2006 and was integrated into the Northern line. The route became Epping ↔ Strathfield ↔ City ↔ Chatswood ↔ Epping ↔ Hornsby, with the section between Berowra and Hornsby now exclusively served by the North Shore line.

In 2013, Sydney Trains was formed and many lines were merged together, including the Northern Line, which was merged into the T1 North Shore, Northern and Western Line. Line numbers were also introduced at this time. The T1 group of lines was assigned the colour yellow.

With the service changes on 28th April 2019 to prepare for the opening of Sydney Metro Northwest, the Northern line was separated from the T1 again into a new line called the T9 Northern Line. As the ECRL became part of Sydney Metro Northwest, the routing again changed to Hornsby ↔ Epping ↔ Strathfield ↔ City ↔ Chatswood ↔ Gordon. The T9 was assigned the colour red, but again a slightly different shade to the colour used by CityRail.

Route
The T9 starts at Hornsby on the Main North line. It then run south through Sydney's northern suburbs to reach Epping, a major transport interchange. There is a siding here for trains to terminate. The line continues south to reach Strathfield, where it merges into the Main Suburban line, the main trunk line that most trains use to enter Sydney's city centre.

The line between Strathfield and Hornsby alternates between two, three and four track sections. These extra tracks are important for ensuring on-time running, as they allow faster trains to overtake slow ones. Intercity and regional trains skip most stations and so need to overtake T9 services, which mostly stop all stations. T9 services also need to overtake frieght trains, because the line is fairly steep and so heavy trains don't move very fast.

T9 trains generally use the middle pair (named 'Suburban') of the six tracks of the Main Suburban line. Services terminating at Central (intercity platforms) use the northern pair (named 'Main') instead. This is neccessary since the Suburban tracks reach their maximum capacity being shared by two lines (T1/9) during the peaks. Trains generally only stop at Strathfield, Burwood and Redfern in this section, with stopping services being provided by T2 trains.

At Central, T9 trains continue onto the North Shore line and over the Sydney Harbour Bridge. They run northward through North Shore region of Sydney and back to Hornsby.

Service
There are generally two off-peak stopping patterns on the T9: Stopping patterns are more varied during the peak and trains run at much higher frequencies. Some trains will skip stations and start/terminate at various intermediate stations, including Epping, Central (intercity platforms), North Sydney, Lindfield and Gordon.
 * Hornsby to Hornsby via City, stopping all stations (4 trains per hour every 15 minutes)
 * Hornsby to Berowra via City, stopping all stations (2 trains per hour)

Note that most trains don't actually terminate at Gordon as shown on maps, but continue following the T1 route to Hornsby or even Berowra.

Platforms screens also never show T9 trains to Hornsby/Berowra via North Shore correctly to avoid customer confusion as the map shows that T9 trains terminate at Gordon. Between Hornsby and Epping, such trains are shown with a destination of Gordon, with a small note that 'Service continues to T1 North Shore line'. The stations after Gordon are hidden because it is faster to change for the Metro at Epping if you are travelling to those stations. After Strathfield, such trains are shown as T1 trains, as passengers need to see the stations after Gordon.

Trains screens will also never show this correctly, but for a different reason. The software driving the screens only knows the train's current run number and will list all the stops from the timetable for that run number. However T9 trains switch from being 'up' (citybound) trains to 'down' (outbound) trains at Central and so also change run numbers. So all stops after Central are not displayed on the internal train screens until the train actually reaches Central.

Services on the T9 Northern Line are run by Waratah A and B Sets and Tangara T Sets. Trains rostered for this line are mostly stabled at Hornsby depot, while some T sets are regularly swapped with Mortdale.

Trackwork services
Whenever the North Shore Line via Gordon is closed due to trackwork, services that normally travel to Hornsby via Strathfield continue onward to Berowra.