The Class 43 HST celebrating 40 years in service.
InterCity 125 was the brand name of British Rail's diesel-powered High Speed Train (HST) fleet, which was built from 1975 to 1982 and was introduced in 1976. An InterCity 125 train is made up of two Class 43 power cars, one at each end of a fixed formation of Mark 3 carriages (the number of carriages varies by operator). The train operates at speeds of up to 125 mph (201 km/h) in regular service, and has an absolute maximum speed of 148 mph (238 km/h), making it the fastest diesel-powered train in the world, a record it has held from its introduction to the present day. Initially the sets were classified as Classes 253 and 254. A variant of the power cars operates in Australia as part of the XPT.
After four decades, most of the HST fleet is still in front-line revenue service under privatisation, and while the InterCity 125 brand name is rarely mentioned officially by the private train operating companies (TOCs), the InterCity 125 still forms the backbone of intercity services on several British main lines. Most sets are to be replaced on InterCity services by 2018 under the Intercity Express Programme. At first, that programme called for some HSTs to continue in use on London to Devon/Cornwall services where there are no plans to electrify the lines. However, in March 2015 it was announced that the remainder of the Great Western fleet would be replaced with bi-mode Intercity Express sets, equipped with the required powerplants and fuel tanks to tackle the distances and inclines of Westcountry services.
The trains currently operate from London Paddington to Penzance, Plymouth, Newquay (summer), Paignton, Exeter, Taunton, Westbury, Oxford, Cardiff, Swansea, Carmarthen, Pembroke Dock (summer), Bristol, Weston-super-Mare, Worcester, Great Malvern, Hereford and Cheltenham; from London St Pancras to Nottingham; from London King's Cross to Inverness, Lincoln, Harrogate, Hull, Sunderland, Leeds, Newcastle upon Tyne and Aberdeen; on the CrossCountry route from Dundee, Glasgow, Edinburgh and Leeds to Plymouth (plus in summer to Paignton, Newquay and Penzance); from Derby to Skegness (summer only) and also Leeds to Aberdeen. One has been converted and has been in departmental use as Network Rail's New Measurement Train since 2003.
Background
In the later 1950s and early 1960s, the British Transport Commission was modernising its rail network. In particular, it wanted to increase intercity speeds, so that the railways could compete more effectively with the new motorways. The government was unwilling to fund new railways, so the BTC focused its attention on increasing line speeds through the development of new trains and minor modifications to the existing infrastructure. A team of engineers was assembled at the Railway Technical Centre in Derby in the early 1960s, with the aim of developing an Advanced Passenger Train (APT), that would be capable of at least 125 miles per hour (201 km/h) and incorporate many features not previously seen on British railways—such as tilting to allow higher speeds on curves.
The APT project had suffered repeated delays, and in 1970, the British Railways Board (BRB) decided that it was not sufficiently developed to be able to provide modernisation of the railways in the short term. Thus, at the instigation of Terry Miller, Chief Engineer (Traction & Rolling Stock), the Board authorised the development of a high-speed diesel train for short-term use until the APT was able to take over. An operational prototype of this train was to be built by 1972.
Prototype
The prototype high-speed diesel train, which was to become the InterCity 125, was to be formed of a rake of passenger coaches sandwiched between two power cars, one at each end. The decision to use two power cars was taken very early in the project as engineers had calculated that the train would need 4,500 horsepower to sustain the required speed of 125 miles per hour on the routes for which it was being designed (the Great Western Main Line, Midland Main Line, and the Cross Country Route), and it was quickly established that no single "off-the-shelf" diesel engine was capable of producing such power. Also a factor in the decision was that the use of two locomotives, operating in push–pull formation, would cause less wear on the rails than a single, much heavier, locomotive. The framework of the new locomotive, classified British Rail Class 41, was built at Crewe Works before being transferred to Derby Litchurch Lane Works for completion. The design of the locomotive incorporated a driving desk fitted around the driver, a sound-proofed door between the cab and the engine room, and, unusually, no side windows. The prototype became the first diesel locomotive in British railway history to use AC alternators in place of a DC generator, with the output converted to DC when used for traction.
The prototype train of seven coaches and two locomotives was completed in August 1972 and by the autumn was running trials on the main line. The following year, high-speed testing was being undertaken on the "racing stretch" of the East Coast Main Line between York and Darlington. The set had been reduced to two power cars and five trailers, and there seems to have been a concerted attempt to see how fast the train would go. On 6 June 1973 131 mph was reached, and this maximum was raised as the days passed. By 12 June a world diesel speed record of 143.2 mph (230.5 km/h) was achieved. The drivers believed that 150 mph was possible but the BRB issued instructions for the high speed tests to cease. It was believed at the time that this was because the BRB wanted to promote the APT as the future of high speed rail travel in the UK.
The fixed-formation concept was proven in trial running between 1973 and 1976, and British Rail decided to build 27 production HSTs to transform InterCity services between London Paddington, Bristol, and South Wales.
Production Versions
The first production power car, numbered 43002, was delivered in late 1975, with a significantly different appearance from the prototype. The streamlined front end lacked conventional buffers, and the drawgear was hidden under a cowling. The single cab front window was much larger than the prototype's, and side windows were included. There was also no driving position at the inner end.
The appearance of the train is the work of British designer Kenneth Grange. Grange was initially approached just to design the livery for the train, but under his own impetus decided to redesign the body, working with aerodynamics engineers. He went on to present the new design to British Rail and persuade them to adopt it.
Key features of the design are the high power-to-weight ratio of the locomotives (1678 kW per ~70-tonne loco),[9] which were purpose-built for high-speed passenger travel, improved crashworthiness over previous models, and bi-directional running avoiding the need for a locomotive to run around at terminating stations. Until the HST's introduction, the maximum speed of British trains was limited to 100 miles per hour (161 km/h). The HST allowed a 25% increase in service speeds along many of the lines they operated.
Introduction into Service
Deliveries continued through 1976, and on 4 October a partial service of HSTs running at 125 mph (201 km/h) began on the Western Region.[12] A radical update of the standard BR livery on the power cars was complemented by the 'Inter-City 125' branding, which also appeared on timetables and promotional literature. By the start of the summer timetable in May 1977, the full complement of 27 Class 253 sets (253001–253027) was in service on the Western Region, completely replacing locomotive-hauled trains on the Bristol and South Wales routes. Passenger volumes on the trains rapidly increased due to the speed and frequency of the service, an effect previously seen only when electric trains had replaced diesel or steam services. The displacement by HSTs of the British Rail Class 50 locomotives to slower services effectively finished off the last 'Western' Class 52 diesel-hydraulics by early 1977.
The production of Class 254 continued through 1977 for East Coast Main Line services. Initially, British Rail planned to fit uprated 2,500 bhp (1,900 kW) Valenta engines to these longer HSTs, but this plan was shelved as the intensive running on the Western Region began to result in a high level of engine failures, often due to inadequate cooling; for a while, the WR power cars were derated to 2,000 bhp (1,500 kW). The Class 254s began to work important ECML expresses such as the Flying Scotsman from the summer timetable in May 1978. Within a year they had displaced the Deltics to lesser workings and reduced the London-Edinburgh journey time by up to an hour.
Production of HSTs continued until 1982,.
Not only did the HST bring considerable improvements in service on the railways, British Rail entered a period of active marketing which accompanied and supported the train's introduction. The InterCity service overall had become a great success for British Rail.