Northern Line (Sydney)

The T9 Northern Line is a commuter rail service operated by Sydney Trains, serving the Northern and parts of the Inner West suburbs of Sydney.

Since 2019 the line has been numbered T9 and is coloured red on maps and wayfinding information.

The traditional Northern Line was the suburban portion of the Main North railway line (Strathfield - Hornsby) which opened in 1886 and was electrified in 1926. When the Sydney Harbour Bridge was opened, it connected railway services from the Main North line and the City underground onto the North Shore line.

Passenger services used to operate as the Main North Line (same name as the physical railway line) and was colour coded red on railway maps. It operated all the way to Cowan, until the service was truncated to Berowra in January 1992. The service, along with the North Shore Line service (yellow), later also ran along the North Shore railway line towards the City via the Harbour Bridge, forming a continuous loop via Strathfield, Epping and back to Hornsby.

In later years, the line operated as the Northern Line and ran from Hornsby to North Sydney via Strathfield and the City, with the North Shore line replacing services between Hornsby and Berowra. In February 2009, the Epping to Chatswood rail link was opened. In October 2009, the Northern Line service was integrated with the shuttle service between Epping and Chatswood. As a result, the traditional Northern Line was split in two, with trains from north of Epping operating via the new link, approaching the city via the North Shore Line and rejoining the traditional route before terminating at Epping.

In October 2013, the Northern Line, North Shore Line and Western line were merged to form the T1 North Shore, Northern & Western Line, which was colour coded yellow.

On weekdays, trains from the upper Northern Line (Hornsby via Macquarie University) joined up with the Western Line trains towards Richmond or Emu Plains, while trains from the lower Northern Line (Epping via Strathfield) joined up with the North Shore Line trains towards Hornsby or Berowra. On weekends, trains ran similar to prior to merger, where the lower Northern Line trains from Epping continue onto the upper Northern Line trains at Chatswood into Hornsby via Macquarie University.

In September 2018, the Epping to Chatswood line closed in order to be converted to metro standards as part of the Sydney Metro Northwest project. As a result, the traditional Northern line branch from Hornsby to Central via Strathfield was reinstated.