London Underground 1996 Stock

The London Underground 1996 Stock is a deep tube train used on the Jubilee Line and one of the newest trains currently running on the network. They were built by Alstom and began service in 1997. They are similar to the 1995 Stock used on the Northern Line, having been built at a similar time by the same manufacturer.

Overview
There is a degree of confusion with regard to the manufacture and delivery of the Jubilee Line's 1996 stock and the Northern Line's 1995 stock. The development programmes for both stocks was run in parallel, with detail design work undertaken by Alstom in the UK at their Birmingham and Rugby facilities, with the first six train sets manufactured in Alstom's Barcelona factory to the 1996 Stock Jubilee Line design. All type approvals for the design were conducted on these early train sets. The production of the 1995 Stock for the Northern Line subsequently followed from the factory in Barcelona. The balance of the 1996 Stock for the Jubilee Line followed the 1995 Stock Production. Both stocks were freighted to Alstom's facility at Washwood Heath in Birmingham for final assembly and equipping, with 1995 and 1996 stock assembled in adjacent production lines.

The 1996 Stock was bought to support the opening of the Jubilee Line Extension (JLE) from to. However, delays in the JLE's opening meant that 1996 Stock was introduced, completely replacing the existing fleet of 1983 Stock, between Christmas Eve 1997 and July 1998 - over a year before the JLE was opened. The existing trains (1983 stock) were originally planned to be refurbished with the same exterior and interior as the new stock (1996 stock) even with double doors, but the cost proved prohibitive.

The 1995 and 1996 Stock trains, while similar, have different interiors, seating layouts and cab designs designed by Warwick Design Consultants. Other differences include different traction packages (Alstom ONIX system on 1995 Northern Line stock), Train Management Systems, slight differences with Tripcock geometry and the use of LED body-side lights on the 1995 Northern Line Tube stock while 1996 Tube stock uses filament bulbs. The most apparent difference between the two stocks is the bogie. The 1996 Stock utilises an Alstom bogie with a rubber suspension whereas the 1995 Stock has fitted AdTranz (now owned by Bombardier) bogies with air suspension to cope with the arduous track conditions encountered on the underground portions of the Northern Line. The main technical differences occurred because the 1996 Stock was designed as "Cheapest first cost" for LUL, while the 1995 Stock was designed for "Life Cycle Cost" as Alstom had won the contract to act as service provider and maintainer of this stock. Alstom subsequently won the maintenance of the 1996 Stock to be carried out at the newly constructed Stratford Market depot in East London.

The 1996 Stock is operated with a dead man's handle at the driver's right hand. When the train is stopped the top of the handle is turned away from the position in which the driver holds it. To depart the driver turns the top of the handle and pushes the red lever forward. The trains were originally designed for automatic train operation as on the Victoria and Central Lines, using a Westinghouse system, however, due to operational problems with the system and the cost of upgrading the signalling line-side infrastructure, this system will never enter service. A new system based on the Alcatel SelTrac as used on the Docklands Light Railway has been installed across the fleet; this is the first application of this system on an underground mass transit line and is referred to as Transmission-Based Train Control (TBTC). This is a 'moving block' system that will allow trains to run faster and closer together without compromising safety, and is crucial to allow Tube Lines to meet future timetable and passenger loading targets.

The original seat covers were a mauve and grey moquette. They formed the letter 'J' for Jubilee, as much as the Northern Line's moquette forms the letter 'N'.

In November 2005 the old cars were refurbished and these seat covers were replaced with the new dark blue Tube Lines moquette. This features multi-coloured and multi-size hollow squares. The new cars were ordered with this moquette. The Piccadilly Line's 1973 Stock also has this moquette, and it has also now been introduced on the Northern Line stock. The armrests were purple but have been repainted blue to match the new seat covers. However, the new (mark 2) trains delivered in late 2005 were still carrying the old internal layout as of December 2008.

The 1996 Stock as originally delivered consisted of six car trains, with two three car units coupled together. Each unit consists of a Driving Motor car [DM], Trailer car [T], Uncoupling Non-Driving Motor car [UNDM], with a standard train formation of DM-T-UNDM+UNDM-T-DM. Twelve of the later build trailer cars had de-icing equipment installed and are referred to as De-Icing Trailer cars [DIT].

The trains are numbered with both 'odd' and 'even' ends. The number comprises five digits. The first two digits are the stock type [96]. The third digit refers to the car type: 0 or 1 DM, 2 or 3 T, 4 or 5 UNDM. 7 indicates a DIT. For example, a six car train set would be 96001, 96201, 96401, 96402, 96202, 96002. In the design, each car is given a letter designation. The even cab end car is A, odd cab end car is B, even UNDM is C, odd UNDM is D, trailer cars are E, DIT is F.

Addition of seventh car
During early 2005, London Underground announced that it would be adding a seventh car to the trains of the existing Jubilee Line fleet, and also adding four new complete trains. With the original factory having been closed on the Barcelona beach front, the four new train sets and sixty three new trailer cars were manufactured in Alstom's new factory at Santa Perpètua de Mogoda in the Barcelona suburbs. The four new trains were built as six-car trains and then modified at the Stratford Depot maintenance facility to the seven-car configuration.

So from 25 December 2005, the line was closed for completion of the seventh-car conversion, including signalling alterations and software modification to the platform edge doors on the JLE. The original plan was to hard wire two cars together so that the onboard computer would "see" them as one car, but this proved not to be necessary. Since the 1996 Stock had been designed as a seven-car train set with the ability to add a seventh car to the trainset if necessary, the platforms were already long enough for seven-car trains throughout the line, and the JLE platform edge doors had been built with space for a seventh car. The line was scheduled to close for five days, but the work by Alstom and Tube Lines was completed ahead of schedule, enabling the line to re-open two days early. The new carriage is a trailer car in the "odd" unit with design designation "G". An example of a seven-car train set would be 96118, 96318, 96718, 96418, 96419, 96219, 96119. [seventh car in bold]

There were various differences between the new and old cars at the time of introduction: Many of these are likely to change as the old cars undergo refurbishment. The new trailer cars are numbered 96601 to 96725 (odd numbers only). The door seal on the new cars still reads "1996", because of the national production rules. However they feature the newer Alstom logo, instead of GEC Alstom.
 * Amber passenger information displays (PIDs) instead of red
 * Black vestibule floor instead of grey
 * Yellow strip on door seal
 * Better fitted seat covers
 * The ridged vestibule floor extends the width of the car

The refurbishment design was carried out by Warwick Design Consultants who also designed the moquette. They were also responsible for the Northern and Picacdilly Line refurbishment designs including the driver's cabs and controls.

Following the introduction, an upgrade to the passenger information system has been introduced, resulting in next station announcements playing on approach to stations.

Digital voice announcements
The Jubilee Line stock is fitted with a digital voice announcement system and dot-matrix displays to provide passenger information.

The voice announcement system makes use of three voices: one female voice for station announcements, another female voice to announce the train's destination, and a male voice for alerts such as, "please keep your personal belongings with you, at all times." Announcements are made when approaching a station and when standing at the platform. Listed below are the announcements that play on a Jubilee Line train traveling from Waterloo to St. John's Wood:

"Approaching Waterloo: 'The next station is Waterloo. Change for the Bakerloo, Northern and Waterloo & City Lines, and National Rail services.'"

"Upon arrival at Waterloo: 'This station is . Change here for the Bakerloo, Northern and Waterloo & City Lines, and National Rail services.' 'This train terminates at Stanmore.'"

"Approaching Westminster: 'The next station is Westminster. Change for the Circle and District Lines. Exit for Westminster Abbey and Houses of Parliament.'"

"Upon arrival at Westminster: 'This station is . Change here for Circle and District Lines. Exit for Westminster Abbey and Houses of Parliament.' 'This train terminates at."

"Approaching Green Park: 'The next station is Green Park. Change for the Piccadilly and Victoria Lines. Exit for Buckingham Palace.'"

"Upon arrival at Green Park: 'This station is . Change here for the Piccadilly and Victoria Lines. Exit here for Buckingham Palace.' 'This train terminates at .'"

"Approaching Bond Street: 'The next station is Bond Street. Change for the Central Line.'"

"Upon arrival at Bond Street: 'This station is . Change here for the Central Line.' 'This train terminates at .'"

"Approaching Baker Street: 'The next station is Baker Street. Change for the Bakerloo, Hammersmith & City, Circle and Metropolitan Lines.'"

"Upon arrival at Baker Street: 'This station is . Change here for the Bakerloo, Hammersmith & City, Circle and Metropolitan Lines.' 'This train terminates at Stanmore.'"

"Approaching St. John's Wood: 'The next station is St. John's Wood.'"

"Upon arrival at St. John's Wood: 'This station is St. John's Wood.' 'This train terminates at Stanmore.'"

The regular dot matrix pattern at Green Park is as follows:

"'Green Park' - 'Destination : Stanmore'"

In between stops, the announcements will also scroll across the displays.

The disparity between the voices used for each part of the announcements is due to the fact that whilst the original recording has been retained for the "This train terminates at... station" announcement, the station announcements have been modified since the installation of the DVA system. The occasional use of a male announcer for general passenger alerts and information like station closures makes the Jubilee Line the second line on the London Underground to use a male voice in its DVA system.

Traction control
1995 stock and 1996 stock have similar bodyshells and were both built by Alstom. However, they use different AC traction control systems. The control system on the 1995 stock is more modern than the 1996 stock, reflecting the fact that the latter's design spec was 'frozen' in 1991.

The 1996 stock uses three-phase induction motors fed from a single-source inverter using a GTO (gate-turn-off) thyristor, derived from those on Class 465 Networker trains. The 1995 stock, for comparison, uses Alstom's "Onix" three-phase Insulated Gate Bipolar Transistor drive.

Earlier London Underground stock, like most electric trains until the 1990s, used DC motors. These are now regarded as inefficient, partly because they are traditionally controlled by resistors, and partly because a 3-phase AC induction motor can provide higher specific power and volumetric power density. The brushes and commutator of a DC motor are a wear item and require regular maintenance, whilst an induction machine has neither.

However, in an AC motor supplied by a fixed-frequency supply, maximum torque can only be achieved when the resistance of the rotor windings equals the reactance. AC motors in an industrial setting tend to be operated at approximately constant speed and therefore large banks of resistors can be used on start-up to raise resistance and maintain torque, if a wound-rotor machine is employed. This would not be efficient in a small motor designed for stop/start operation.

As a result, it was only the invention of electronic control systems from the 1980s onwards that made AC traction viable for trains. The motor can be supplied using an inverter, and by varying the inverter's output frequency it is possible to keep the frequency of the currents flowing in the rotor windings constant, and hence the reactance. (note the reactance depends on frequency whereas the resistance is fixed)

The GTO thyristor used on 1996 stock achieves this by 'chopping' the supply voltage in order to drive a sinusoidal current in the motor windings (PWM), creating the characteristic audible whine associated with the stock and with the Class 465 Networker trains that share its traction drive system. The noise timbre changes as the pulse length changes. The noise is produced by the switching frequency current ripple and resulting torque pulsation experienced by the rotor of the induction machine.

More modern AC traction, such as the 1995 stock, uses the IGBT (which is essentially a combination of the MOSFET and the BJT), which can operate at much higher switching frequencies than the GTO. The 'whine' effect is far less noticeable due to the higher switching frequency of IGBT drives.