Sydney Trains M set
The Sydney Trains M sets, also referred to as the Millennium trains, are a class of electric multiple units that operate on the Sydney Trains network. Built by EDi Rail between 2002 and 2005, the first sets initially entered service under the CityRail brand on 1 July 2002 after short delays due to electrical defects. The M sets were built as "fourth generation" trains for Sydney's suburban rail fleet, replacing the 1960s Tulloch carriages and providing extra capacity on the suburban rail network. The sets currently operate on the T2 Inner West & Leppington, T3 Bankstown , T5 Cumberland, T7 Olympic Park and T8 Airport & South lines. Design. The Millennium train, like the entire Sydney Trains fleet and electric NSW TrainLink fleet, is a double decker. It is a four car consist, with the middle two cars being non-control motor cars and the two outer cars being driving control trailer cars fitted with the pantograph. The Millennium train was the first to be equipped with an AC drive system unlike the Tangara, which has a DC drive system. The sets usually operate in eight-car formations with two four-car sets combined. While the Millennium train  concept is an evolution of the Tangara concept (manufactured by A Goninan & Co), the Millennium train introduced new features such as internal electronic destination indicators, automated digital voice announcements for upcoming stops, a return to reversible seating, surveillance cameras, wider stairways, a new safety yellow colour scheme, and push-button opened internal doors. The Millennium Train also introduced crumple zones to absorb impact in a collision. Interiors were designed by Transport Design International. The train also features emergency help points, allowing passengers to contact the train crew in an emergency. The help points are located on the sides of the  stairwell to the upper deck. There are actually two help points in the same location, with a large one at face height with a microphone and speaker, and a lower one with a microphone only. There are also emergency door releases which were retrofitted to the trains. These allow passengers to manually open the doors in an emergency, as recommended in the report for the Waterfall rail accident. The retrofit program was stated as having been completed in November 2014. Like the Tangara and the Waratah trains, the Millennium train features Scharfenberg couplers. M sets are 3030mm wide, being  classed by Transport for NSW as medium width trains. This allows them to operate within the whole Sydney Trains suburban network, as well as the entire (electrified section) of the South Coast Line and Central Coast & Newcastle Line. They were also able operate on the Blue Mountains Line between Central and Springwood prior to the 2020-21 widening for the D Sets, and are now able to operate to Lithgow. While these are all possible for them, as they are suburban trains they are not scheduled to do so. Unlike sets M2-M35, set M1 has a slightly different interior  design with differently coloured doors and different seat handles for unknown reasons. Delivery. The cars were constructed by EDi Rail at Cardiff Workshops. The contract included a 15-year maintenance agreement with EDi Rail to maintain the trains at a specialised maintenance centre at Eveleigh. During testing and initial revenue service, they ran as four car sets, with eight car sets commencing service towards the end of 2002 after further testing. All 35 four car sets were delivered by October 2005. The initial order signed in October 1998 was for 81 carriages, in December 2002 an option was taken up  for an additional 60. In February 2017, Sydney Trains exercised an option to extend Downer's maintenance of the trains for a further 10 years. Criticisms. The Millennium trains were criticised for having several technical problems and causing problems with Sydney Trains, they were referred to in the media reports as The "Mi-lemon" and "Millenni-Bug" as a result. Some of the problems were caused by insufficient power supply on the overhead to cope with the power demands of the more technologically advanced trains causing them to shut down. Software bugs also contributed to the trains' poor reliability. The  Millennium trains were withdrawn from service in April 2003 while the problems were being rectified and a full audit was carried out. They were subsequently reintroduced into service in June 2003 and have since been operating on the T2 Airport, Inner West & South, T3 Bankstown, T6 Carlingford and T7 Olympic Park lines. After the new timetable was released on 26 November 2017, M sets began as 4-car services on the T5 Cumberland line on both weekdays & weekends, along with a few 8-car Waratahs. In service. External Carriage Camera Trial. In late 2008, two Millennium trains were fitted with  external cameras atop of carriages near the doors, testing their use for the then-future Waratah trains. These cameras were subsequently incorporated into the final design of the Waratah train. Lines serviced. The Millennium trains typically operate on the following lines (normally described as Sector 2): Maintenance Depots. The trains were originally maintained at Eveleigh Maintenance Centre. As with all other trains, these trains are not exclusively kept in Auburn overnight. They only need to return to the depot for maintenance, and at other times, they may be stabled at various yards on the lines that they operate, such as  Liverpool and Leppington yards.