The British Rail Mark 4 is a class of passenger carriages built for use in InterCity 225 sets on the East Coast Main Line between King's Cross, Leeds and Edinburgh. Withdrawals began in 2019, with some being sold for further use with Transport for Wales between Cardiff and Holyhead.
History and construction
A small build compared with the Mark 2 and Mark 3 designs, 314 Mark 4s coaches were built between 1989 and 1992 by Metro-Cammell's Washwood Heath factory to operate services on the newly electrified East Coast Main Line. They were operated by London North Eastern Railway and its predecessors in 30 fixed formations of nine carriages, with a Class 91 locomotive and Driving Van Trailer.
The Mark 4 is an all-steel coach incorporating a number of improvements over the Mark 3 stock - notably the inclusion of automatic push-button operated plug-type doors, in place of manually operated slam-doors, fully sealed gangways and controlled emission toilets (CET). Body shells were built by British Rail Engineering Limited (BREL) and Società Italiana Ernesto Breda.
After a period of evaluation in 1988, Swiss SIG type BT41A bogies were selected rather than BREL Type T4 bogies when BREL could not provide commercial guarantees on the demanding lateral ride comfort required for running (BT41B/C refer to the bogie types used on the Mk4 DVT).
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 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 plus four flip-down seats per vestibule (since removed and replaced with bench style perch seats).
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 profiled sides, intended to allow the retrofitting of tilt-equipped bogies derived from the APT. This would have allowed up to 6° of tilt; modified coaches would have been designated Mark 4 T, but this plan was abandoned in January 1986. The 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, but after the failure of the InterCity 250 project to gain Treasury support, British Rail ordered a small number of Class 90 locomotives to supplement existing locomotives on the West Coast Main Line.
The Mark 4 has gained widespread praise 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; the Mark 4 is derived from the Class 156.
The Iarnród Éireann Mark 4 push-pull carriages, introduced on the Irish railway system in mid-2006, are of a different design; they were manufactured by the Spanish manufacturer CAF.
The Mark 4 was the first British Rail vehicle not to use Rail Alphabet typeface for interior signage and operating notices.
Via Rail Canada's Renaissance fleet of inter-city and sleeper coaches are derived from British Rail's Mark 4. They were built for the abortive Nightstar services to Europe and were adapted by Bombardier Transportation to meet Canadian requirements.
Project Mallard
Between October 2003 and November 2005, Bombardier Transportation, under contract from GNER, rebuilt and refurbished the carriages under Project Mallard. Trains with rebuilt coaches became known as Mallards to distinguish them from unrefurbished sets during the upgrade programme, named after the steam locomotive Mallard, built in the 1930s by the London and North Eastern Railway and holder of the world speed record for steam locomotives.