Siemens Nexas EMU (2002)

The Siemens Nexas is a class of electric multiple units manufactured by Siemens Transportation Systems for the suburban railway network of Melbourne, Australia between 2002 and 2005. The design of the trains was based on the Siemens Modular Metro.

History
In March 2000 M>Train ordered 62 Siemens Nexas trains to fulfill a franchise commitment to replace its fleet of Hitachi trains.

The original order was for 62 3-car sets, with an option for an additional ten 3-car sets. In December 2002 just before the first was delivered, National Express handed the M>Train franchise back to the Government of Victoria, thus the first Siemens Nexas' were delivered to the government. All passed to Connex Melbourne in April 2004. The option for ten additional trains was exercised in August 2005, with the last of these delivered in January 2006.

Siemens Rail Services was contracted to provide maintenance of the trains for a period of 15 years (subject to refranchising) at Newport Workshops. With the refranchising of the network to Metro Trains Melbourne in 2009, this maintenance arrangement was retained for an initial three-year period.

The first entered service on 21 March 2003 with the last delivered in January 2006.

In December 2014, Siemens Nexas 831M-2566T -832M with a reduced seating layout added extra hand rails layout at the doors.

Braking issues
In late 2006 the trains suffered a number of braking discrepancies while in service; 14 trains overshot platforms in the space of three days. The 15 units involved in these overshoots were withdrawn from service for checks, and instructions were issued to the drivers to minimise further occurrences. By mid-January 2007, a total of 24 three-carriage trains had been impounded for testing after 20 further incidents of over-running stations since 22 December 2006.

On 13 January 2007, Connex stopped running the Siemens Nexas trains as 3-car sets until the braking issue was resolved, with the result that all services (including evenings and weekends) were operated by 6-car trains. On 29 January 2007, Connex cancelled 37 peak-period services until further notice, due to the shortage of operational trains.

By 1 February 2007, 38 three-car sets were withdrawn due to continuing braking failures, meaning that almost half of the Siemens Nexas fleet (or around 10% of the total fleet) was out of revenue service. Amidst the media reporting an escalating problem with the risk of the entire fleet potentially having to be suspended, Siemens issued a statement on 31 January 2008 saying that they believed there had been no evidence during investigations of the braking failures that would require the entire fleet of trains to be withdrawn from service. Testing of affected trains was carried out on the Werribee line between Newport and Laverton, with soapy water sprayed onto the rails to increase the amount of wheel slip experienced, in an effort to replicate the brake fault. The entire fleet has now re-entered service, although with a restriction not to run single unit (3 car) operations.

In December 2008 train operator Connex commenced proceedings in the Supreme Court to claim damages from Siemens. Connex claims Siemens provided trains with a braking system that was "defective, faulty and inadequate", the trains being "not fit for their purpose" and were not of "merchantable quality".

In March 2009, it was reported that three Siemens Nexas trains had been impounded due to new braking incidents in the week prior.

By December 2010 sanding equipment was trialled on set 773M-2537T-774M in order to improve braking performance of the trains, and by February 2011 a number of in-service trains had also been fitted with the equipment. The sand boxes are fitted to the middle two bogies of each 3-car set.

In June 2011 installation of sanding equipment was completed across the entire fleet. Speed restrictions have now been lifted on all Siemens Nexas trains.

In September 2011 the Office of the Chief Investigator for transport safety found that "the relatively high frequency of overruns involving Nexas trains was neither the result of individual train defects nor any deficiency in train maintenance".

Design & Construction
The bodies of the Siemens Modular Metro trains evolved from the 1993 DT2 Series used in the Nuremberg U-Bahn whose design in turn came from production of the A Series built for the nearby Munich U-Bahn, but now also used in Nuremberg.

The version of Siemens metro train designed for Melbourne included several attributes similar to existing Melbourne suburban electric trains such as being single-deck and operating in M-T-M (motor-trailer-motor) sets of three carriages, where the motor cars each have an overhead pantograph, and two of these 3-car sets are generally coupled together to form a 6-carriage train when run in revenue service, though a single set may be run when demand does not merit a full train.

All were built by Siemens Transportation Systems, Vienna with the final fitout completed at Newport Workshops.

There are several notable differences between the Siemens Nexas trains and other trains which operate in Melbourne. These include:
 * 2+2 seating. All other trains had 2+3 seating, however X'Trapolis 100 trains ordered as part of the 2008 Victorian Government Transport Plans have the same 2+2 seating configuration, and existing X'Trapolis trains had their seats modified to a 2+2 configuration as part of the franchise agreement.
 * Two doors per carriage per side. Being significantly wider they were theorised to be slightly more efficient in loading and unloading passengers, although this is disputed by some sources, who believe the fewer doors lead to longer platform dwell times compared to the three smaller doors in other Melbourne trains.
 * Plug-type doors - hinged outward and slide along the outside of the vehicle when opening.
 * Extreme smooth, vertical walls.
 * Open articulation. Passengers can freely move from carriage to carriage, within a 3-carriage set, without opening doors, the first such train with this configuration in Melbourne.

The Siemens Nexas' are fitted with Passenger information system produced by the German firm Annax. The system does not announce service details at the commencement of a journey, express running or the end of services.

In June 2008 Connex started a program to replace the seat coverings in a number of Siemens trains, using the same type of fabric as used in the X'Trapolis 100 trains, Metro Trains Melbourne has since put in new seating fabric displaying various stations around the network, to almost half the fleet.

Refurbishment
In 2016 Metro Trains Melbourne began refurbishing the interior carriages of Siemens trains. All windguards and glass screens were removed from the doorways and replaced with a smaller vertical handrail (except where wheelchair access is required), a number of seats removed near the doors and extra vertical and horizontal handrails fitted to improve comfort and capacity. A cleaning program occurred at the same time, which included fitting new seat pads and covers, re-painting walls and applying anti-graffiti film to the windows. As of August 2017, the entire fleet had been refurbished. A similar refurbishment has been completed on the older Comeng trains.

Liveries
The Siemens trains have a stainless steel body, and were seen in a number of different liveries in their early years, owing to the changes in ownership that have occurred while the trains were entering service.

The trains were originally delivered with M>Train blue and green stripes on the side, and the M>Train 'swirl' on the front fairing. Later deliveries entering service in bare metal on the sides, and white front fairings with a green and yellow striped bar. On entering Connex Melbourne ownership, blue and yellow stripes were progressively added to the side of all trains, and front fairings were repainted yellow with the blue Connex logo.

After Metro Trains Melbourne took over the operation of the suburban network in November 2009, the Connex logo on all trains was covered over as a temporary measure, with all sets progressively being repainted into Metro livery, a process completed in March 2010.