|Status||Open, passenger only|
|Locale||Wellington, New Zealand|
|Ridership||1,119,000 per annum (2011–12)|
|Opened||24 September 1885 (as Wellington & Manawatu Railway)|
Greater Wellington Regional Council (stations)
|Rolling stock||Matangi class electric multiple units|
|Line length||10.49 km|
|Number of tracks||1 with 3 crossing loops|
|Track gauge||3 ft 6 in (1,067 mm)|
|Electrification||1600 V DC overhead|
|Operating speed||64 km/h (maximum)
40 km/h (in tunnels)
|Highest elevation||152 m (Raroa)|
The Johnsonville Branch known as the Johnsonville Line, is a commuter branch line railway from the main Railway Station of Wellington, New Zealand to the northern suburb of Johnsonville via Ngaio and Khandallah.
The line was built in the 1880s as part of the private Wellington and Manawatu Railway Company line to connect Wellington to Longburn. Construction started in 1879, and the first section, to Paremata, opened on 24 September 1885. The line became part of the North Island Main Trunk when the government bought the WMR in December 1908.
The line was used by railway workers from the Tarikaka Settlement in Ngaio, including early shift workers who needed to fire up steam locomotives at the Wellington depot.
Two experimental RM class railcars were briefly used on the line as NZR sought to develop economically viable railcar technology. The Westinghouse railcar was introduced in 1914 and served through to 1917. The Thomas Transmission railcar was introduced in 1916 and operated sporadically into the early 1920s. Both railcars struggled on the steep grades and revealed that further advances were needed to make railcars suitable to New Zealand's conditions.
The line became a branch when the Tawa Flat deviation of the NIMT opened to passengers in 1937, and was sometimes called The Hill (in NZR jargon). The line was electrified at 1500 V DC overhead supply, and the new service with the new English Electric DM/D class electric multiple units service started from Monday 4 July 1938, after an opening ceremony on 2 July. The units normal operate as two-car motor/trailer sets, or four-car sets in peak hours. Additional DM/D class units were ordered for the line in 1942 and supplied in 1946.
The line was terminated in Johnsonville, about 100 m beyond the end of the current line: the State Highway 1 motorway on-ramp follows the route of the old line. Ngaio and Khandallah stations already had crossing loops, and a third crossing loop (without platform) at Wadestown plus new stations at Awarua Street and Simla Crescent were added. The two new stations had been used by steam trains from 10 January 1938, though only some local trains stopped there (on request).  
The line was reviewed in 1984, 1993 and 2006–07 to consider either closing or upgrading it, without any significant changes being made.
A half-hourly service runs daily, augmented to a 13/13/26-minute pattern at peak periods.
The line has been passenger-only since the termination of livestock trains for an abattoir in the Ngauranga Gorge. The livestock were originally driven on foot through Johnsonville streets, but after protests sidings near Raroa were opened on 2 February 1958. The livestock traffic ceased about 1973, though the sidings at Raroa were not lifted until about 1982. Because of the sharp curves on the line, EW class electric locomotives were used for livestock trains instead of the earlier ED class locomotives, which were hard on the track with their long rigid wheelbase.
The line is single track through very steep terrain rising 150 m above sea level in its 10 km length, with the highest point (152 m) at the north end of Kaka Tunnel. The ruling grade is 1 in 36, with long sections from Wellington to Crofton Downs of 1 in 40. There are seven narrow tunnels, six bridges, and three passing loops There are three level crossings with half-barriers; at the Simla Crescent and Khandallah stations, and at Fraser Avenue between Khandallah and Raroa stations (the Fraser Avenue crossing was last to get barriers as well as bells, in 2009). There is a private rail crossing to a house immediately south of the Fraser Avenue crossing; and a pedestrian crossing to Poona Street, Khandallah between the Khandallah station and the Rangoon Street overbridge. Pedestrians can also cross the line at the Ngaio station.
The Wellington City Council let a $1.7m tender to replace the Rangoon Street single-lane overbridge of c1906, which crosses the Johnsonville line, with a two-lane bridge. Work commenced in June 2008 and was completed by December 2008.
Three traction substations along the line take electricity from Wellington Electricity's 11,000-volt distribution network and transform and rectify it to 1500-volt direct current for the overhead traction lines. The substations are located at Wellington (shared with the Kapiti and Hutt Valley Lines), Ngaio and Khandallah.
Upgrade in 2008–2009
The North Wellington Public Transport Study by GWRC and WCC considered four options for improved public transport: enhanced rail; bus on street; conversion to a guided busway; and conversion to light rail. On 16 November 2006 the GWRC Public Transport Committee and the WCC Strategy & Policy Committee accepted a "Do Minimum" option involving retention of the line and replacement of the current DM units with the same number of refurbished EM/ET class (Ganz Mavag) units; this required enlarging the tunnels and increasing platform clearances and lengths. GWRC have since had to change to using only the new Matangi units on this line because of the limited braking power of EM/ET class units on the steep grades
GWRC envisaged (2007) that the track through the tunnels would need to be lowered by 120 mm, depending on the new units. Lengthening of passing loops and platforms was also likely to be needed, and the estimated cost was $5 million. A programme of preparatory work for the tunnel upgrading commenced on 7 September 2008 and was completed in February 2009. Construction took place after 20:00 on Sunday – Thursday nights to minimise disruption to commuters, with services being replaced by buses. The seven tunnels were upgraded in January 2009  during a period in which the line was closed to all traffic. The work included:
- lowering the track and widening the side clearances in the seven tunnels
- lengthening the three crossing loops, allowing longer trains
- upgrading platforms by lengthening them and increasing clearances
- increasing clearances under two bridges: Lower a rail bridge in Ngaio Gorge (between tunnels) and lower the level of the track under the Raroa Station footbridge
- new power substation at Ngaio
New rolling stock
Due to significant mechanical difficulties being experienced by Tranz Metro in keeping the DM/D EMUs in service, several units were withdrawn from service in February 2012. Buses were added to supplement the remaining service capacity pending the planned introduction of the FT/FP "Matangi" EMUs on 19 March 2012. The first Matangi service was the 11:02 departure from Wellington, which passed the last English Electric service on the line at Ngaio station.
The proposed redevelopment of the Johnsonville Town Centre will include improvements to the rail and bus terminal at Johnsonville; the terminal is now referred to as the Johnsonville Hub.
The Broderick Road overbridge immediately south of the Johnsonville Railway Station was upgraded by widening and lengthening in 2015 to include cycle lanes and extra road lanes over it.  Provision is made for dual tracks underneath (currently one track) into the station, as requested by the Greater Wellington Regional Council for future double-tracking. 
- Churchman, Geoffrey B. (1998) . The Story of The Wellington to Johnsonville Railway (2nd ed.). Wellington: IPL Books. ISBN 0-908876-05-X.
- Hoy, D.G. Rails out of the Capital (NZRLS, 1970)
- "Wellington Metropolitan Rail 2011/12 Annual Report" (PDF). Greater Wellington Regional Council. 30 June 2012. Retrieved 23 March 2013.
- "Table 5-1: Public Transport Patronage in the Northern Suburbs". North Wellington Public Transport Study – Stage 3 Technical Evaluation Report (753 KB PDF). Wellington: Greater Wellington Regional Council. 15 November 2006. p. 163. Retrieved 2009-06-09.
- "Railways Department announcement". Evening Post (Papers Past). 8 January 1938.
- *"Railways Department advertisement (go down page)". Evening Post (Papers Past). 8 January 1938.
- http://www.wellington.govt.nz/news/display-item.php?id=3231 (2008)
- "Out with the old in with the new". The Wellingtonian. Wellington: Fairfax New Zealand. 20 August 2008. Retrieved 2008-08-31.
- Wellington City Council (1 August 2008). "Wellington City Council roadworks update". The Dominion Post. Wellington: Fairfax New Zealand. Archived from the original on 2016-12-30. Retrieved 8 December 2009.
- "Order paper for meeting held on 16-Nov-2006 at 11:00 am". Proceedings of the Passenger Transport Committee. Wellington: Greater Wellington Regional Council. 16 November 2006. Retrieved 2010-02-23.
- "Strategy and Policy Committee meeting agenda". Proceedings of the Strategy and Policy Committee. Wellington: Wellington City Council. 16 November 2006. Retrieved 2008-07-09.
- Sinclair Knight Merz (A Bell) (15 November 2006). "North Wellington Public Transport Study TECHNICAL EVALUATION REPORT". Wellington: Sinclair Knight Merz: 164. Archived from the original on 2012-02-23. Retrieved 2010-02-23.
The base case assumes the replacement of the existing English Electric Units with 4-car refurbished Ganz Mavag units operating the same 13-minute, 13-minute, 26-minute timetable. ... This report sets out the minimum works ONTRACK believe are required to enable the larger Ganz Mavag units to operate on the Johnsonville Line. (Section 2.1.1-page 6)
- BLAND, JES (9 July 2008). "70 years of clean green trains on the J'ville line". The Wellingtonian. Wellington: Fairfax New Zealand. Archived from the original on 2012-09-11. Retrieved 2008-07-09.
As for the future of the Johnsonville line, upgrades are already underway to allow for new rolling stock to use to the line in 2010.
- Ontrack staff comment on Johnsonville Line Open Day 4 February 2009
- http://www.gw.govt.nz/Improvements-to-Johnsonville-line-on-the-way/ (16 November 2006)
- "Buses to replace J'ville trains Sunday – Thursday nights". Wellington: Greater Wellington Regional Council. 1 September 2008. Archived from the original on 2012-02-23. Retrieved 2010-02-23.
- "Wellington Regional Rail Programme – Johnsonville Line". ONTRACK. Retrieved 2010-10-26.
- "Johnsonville Line (upgrade)". KiwiRail. Retrieved 2012-02-19.
- "Buses replacing trains – Johnsonville line Dec 28 to Feb5". Wellington: TranzMetro. Archived from the original on 2016-01-20. Retrieved 2008-11-16.
- Wellington Region Rail Programme (Leaflet c2008 from Ontrack/Trans Metro/GWRC)
- STEWART, MATT (3 February 2012). "Old trains pulled from Johnsonville line". The Dominion Post. Wellington: Fairfax New Zealand. Retrieved 4 February 2012.
- SPEER, SOPHIE (19 March 2012). "New hope arrives on the Johnsonville line". The Dominion Post. Wellington: Fairfax NZ News. Retrieved 19 March 2012.
- "J'ville roads get $11m boost". The Dominion Post. Wellington: Fairfax NZ News. 19 March 2014. Retrieved 19 March 2014.
- "new railway overbridge in johnsonville". Wellington City Council. 5 August 2014.
- Hermann, Bruce J; North Island Branch Lines pp 64–67 (2007, New Zealand Railway & Locomotive Society, Wellington) ISBN 978-0-908573-83-7
- New and old units on the Johnsonville Line, 19 March 2012
- "Wellington power supply upgrades (2009–2011)". KiwiRail. Retrieved 2012-02-19.
- Johnsonville Line: Photos, Signalling
- Photo of one of the last main line trains to enter Johnsonville c1938 from The New Zealand Railways Magazine as republished by the NZETC
- Photo of arrival of the first unit at Johnsonville 1938 from The New Zealand Railways Magazine as republished by the NZETC
- Photo of Johnsonville units at Wellington station c1939 from The New Zealand Railways Magazine as republished by the NZETC
- Photo of multiple unit on the line c1940 from The New Zealand Railways Magazine as republished by the NZETC
- A flashlight photo of passengers inside a unit c1938 from The New Zealand Railways Magazine as republished by the NZETC
- Scene from a loco cab running downhill from Johnsonville c1930 from The New Zealand Railways Magazine as republished by the NZETC
- North Wellington Public Transport Study
- Railways of New Zealand: Wellington & Manawatu Railway
- Invitation to Opening (NZR Publicity picture)