British Rail Mark 4

British Rail's fourth design of passenger carriages was designated Mark 4, designed for use in InterCity 225 sets on the newly electrified East Coast Main Line between London, Leeds, and Edinburgh.

History and construction
A small build compared with the earlier Mark 2 and Mark 3 designs, the coaches were built between 1989 and 1992 by Metro-Cammell/GEC-Alsthom at its Washwood Heath works in Birmingham. The whole fleet of 302 vehicles is currently operated by East Coast in 30 fixed formations of nine coaches with a Driving Van Trailer and Class 91 locomotive.

The Mark 4 is an all-steel coach incorporating a number of improvements over the Mark 3 stock that preceded it, notably the inclusion of automatic pushbutton operated plug-type doors in place of the earlier manually operated slam-doors. After a period of evaluation in 1988, Swiss SIG type BT41 bogies were selected rather than BREL type T4 bogies when BREL could not provide commercial guarantees on the demanding lateral ride comfort required for 140 mph running. However during the first year of operation in 1989 complaints were made about the "lively" ride of the coaches. This required modifications to the damper and spring rates of the bogies and the fitting of inter-coach "car coupler dampers" to further improve damping between the vehicles. Disabled access was another priority of the design, so the door vestibules were enlarged to allow a more generous turning circle for a wheelchair. With ever-increasing levels of overcrowding the so-called 'gangway passenger' had become an important consideration, so the vestibule environment was improved with carpeted walls, better lighting, sealed gangways and carriage doors, and four flip-down seats per vestibule (since removed).

Many of these innovations came courtesy of the abandoned Advanced Passenger Train, upon which the Mark 4 was heavily based. This influence was most obvious with the Mark 4's profiled sides, which were intended to allow the retrofitting of tilt mechanism equipped bogies derived from the much criticised APT. This would have allowed up to 6° of tilt; modified coaches would then have been designated "Mark 4 T" but this plan was abandoned by BR in January 1986. British Rail's initial business case for the Mark 4 anticipated them also being operated on the West Coast Main Line as a follow-on order after the East Coast Main Line electrification. After the failure of the InterCity 250 project to gain Treasury support, British Rail ordered a small number of Class 90 locomotives, which were used to supplement existing locomotives on the West Coast Main Line until the introduction of Class 390 'Pendolino' units a decade later.

The Mark 4, like the Mark 3 before it, has gained widespread praise in the railway industry for its exceptional crashworthiness, something that was proven in the Hatfield and Selby crashes, where experts identified the integral construction of the vehicles as being a key factor in restricting the death toll.

The Class 158 and Class 159 diesel multiple units, although superficially similar, are not based on the Mark 4 bodyshell. In fact, the Mark 4 is derived from the Class 156.

Unlike Mark 2 and Mark 3 carriages, the Mark 4 design was not adopted by Iarnród Éireann (Irish Rail); the IÉ Mark 4 push-pull carriages introduced in mid-2006 are of a different design, manufactured by the Spanish manufacturer CAF.

The Mark 4 was the first BR vehicle not to use the iconic Rail Alphabet typeface for any of its interior signage and operating notices.

Project Mallard
Between late 2003 and April 2006 GNER (the former franchise owner) and Bombardier Transportation undertook a rebuilding and refurbishment programme for the Mark 4 stock called Project Mallard. Trains with these rebuilt coaches became known as Mallards to distinguish them from unrefurbished sets during the upgrade programme, named after the Mallard steam locomotive, (which was built in the 1930s by the London and North Eastern Railway and holds the world speed record for steam locomotives).

The Mallard refit gave the Mark 4 coaches all-new interiors with new seats, carpeting and power points at every seat for charging laptops and powering appliances. The vestibule areas lost their flip-down seats near the entrances with perch-type seats being put in their place. As part of the Mallard programme the buffet coach in each set was turned around and half-converted to provide more standard-class seating. Wheelchair-width doors were fitted and the overall seating capacity of a full-length train was increased by fitting airline-style seats in place of the previous groupings of pairs of seats facing each other across a table.

The buffet was remodelled as 'cafe-bar' in a similar style to the 'shop' concept developed by Virgin on their Voyager and Pendolino trains. However, the range of products offered by GNER was smaller than on Virgin trains: they did not sell CDs or magazines, for example.

GNER introduced wireless Internet connectivity as a trial from December 2003 and introduced it into service from April 2004 making it the first service of its kind in the United Kingdom (similar services are now offered by Virgin Trains and Southern). All Mallard trains now offer 802.11b/g wireless LAN access to the Internet. Prior to National Express East Coast (NXEC) taking over the franchise on Sunday 9 December 2007 access to the Internet was free in first class and chargeable in standard class. With the advent of the new franchise access to the Internet became free for all passengers. In October 2010, under the temporary Directly Operated Railways ownership, East Coast reintroduced charges for standard class passengers.

2010 refurbishment
Beginning in 2010, the Mark 4 coaches were externally refurbished with a new livery to replace the existing mix of GNER/NXEC liveries. The new livery was applied using vinyls over the old paintwork during a vehicle overhaul at Wabtec Rail in Doncaster. The livery, which has been dubbed 'Silver Link', is similar to the one used by National Express East Coast during its brief tenure on the route.