From Britomart to Newmarket, Western Line services travel on the Newmarket Line, then follow the North Auckland Line to Swanson, the current northernmost station on the network.
History
By the early 20th century, an intensive suburban service ran between Auckland city centre and Henderson, with some mixed trains progressing to Helensville via Waitakere. When the mixed trains were withdrawn, Helensville became New Zealand's northernmost passenger terminus with a daily service to Auckland. However, in February 1980, the Minister of Railways, Colin McLachlan, announced it would be cancelled due to a lack of rolling stock. On 18 August 1980, a new timetable was implemented – it eliminated the Helensville service, with Waitakere becoming the new terminus. At the same time, the stations at Westbrook, Croydon Road, and St George's Street were closed to suburban traffic on a trial basis that was later made permanent. ADK and ADL classes of diesel multiple units were purchased in 1993 to replace locomotive-hauled carriage trains. In 1997, as the DMUs stimulated increased patronage, work was undertaken by Auckland Regional Council to extend platforms so that longer trains could be accommodated. To enable more frequent services, construction began on 9 April 2004 to double track the line between Mount Eden and Morningside. When this new track entered service, a new timetable was introduced on 14 February 2005 with more frequent trains between Britomart and Waitakere, particularly during peak periods. This timetable also introduced short run services between Britomart and New Lynn. This was followed by the opening of a new double platform Kingsland station on 21 May 2005, replacing the old single platform station. Further patronage growth meant that on 25 October 2005, another new timetable was implemented and it featured the re-introduction of features that had been absent for many years, including express services from Waitakere to Britomart on weekdays and Sunday trains between Britomart and New Lynn. The weekday service frequency to Swanson was cut to 37 minutes, but this meant trains to Waitakere ran only every 74 minutes. ;Helensville trial Beyond Waitakere, services between Auckland and Helensville resumed in July 2008 on a trial basis, with a minimum of forty passengers daily required for the train to be permanently reinstated, but the service was terminated again in December 2009, because an average of only 43 passengers per day used the three daily services, requiring a much above-average subsidy. ;Double-tracking The first section of the duplication had been undertaken by Auckland Regional Council, as 'Project Boston', adding 2.2 km of double track between Boston Road Station and Morningside Station by early 2005. In May 2005, work began to prepare the rail corridor between New Lynn and Henderson for double tracking and construction of the double track commenced on 31 December 2005. On 19 December 2006, the central government approved a NZ$120 million package for double trackage in the other direction from New Lynn to Avondale; this included a 1 km long, 8 m deep trench through the centre of New Lynn for which construction began in 2009. On 8 June 2010, the double tracking of the Western Line was completed, enabling trains to run in both directions on one of two tracks all the way between Britomart Transport Centre in the Auckland CBD and Swanson station in Waitakere. The double-tracking cost $420 million and employed around 400 people. The last section was a 3 km stretch between Avondale Station and Titirangi Road in New Lynn. From the completion of the electrification of Auckland's suburban network in July 2015, services ceased on the non-electrified section of track between Waitakere and Swanson stations and were replaced by buses. This made Swanson the current northwestern terminus on the Western Line, as considering the low passenger numbers at Waitakere Station, increasing the height in the Waitakere Tunnel was not considered justified. Waitakere Village is now served by bus services connecting to Swanson and Henderson. ;Additional Station On 12 March 2017, Parnell Station was opened to Western Line services.
Services
Suburban services are operated by Transdev under the AT brand.
