British Rail's Prototype APT

British Rail's Prototype Advanced Passenger Train

The following is reproduced from a leaflet titled "British Rail's Prototype Advanced Passenger Train
Providing InterCity Technical Developments

PDF English (1.80MB)


The APT is a vital part of the InterCity plans for the future. 1984 was particularly successful for APT. Since August 1984 APT formations have been used to supplement ordinary service trains between Glasgow and London in addition to their continued use in engineering testing and development.

The present APT trains were built as prototypes for a fleet of similar trains. They commenced test running in 1977. As a result of a changed business requirement the production trains (codenamed InterCity 225) will be of the more conventional formation shown below with a single Class 91 locomotive hauling a rake of up to 11 coaches and a non-powered driving trailer.

APT remains however an indispensible high speed testing and proving bed for potential systems for the IC225.


In addition to significant mileage accumulation running (the Glasgow based train ran some 75,000 miles during 1984) APT-P has been used to carry out a number of special test programmes. For instance in late 1983 the feasibility of current collection at speeds of up to 160 mph with existing over-head line equipment was demonstrated on the West Coast Main Line (WCML) between Beatock and Lockerbie and up to date data on train resistance at high speeds has also been obtained on the York to Northallerton section of the East Coast Main Line (ECML).

Additionally APT-P was used on April 7 1984 to complete a series of passenger comfort trials, the results of which have been used as a basis for the tilt performance specification for the next generation of tilting trains.

On 12 December 1984 British Rail's committment to reduced journey times was highlighted by a record breaking journey from London to Glasgow - the 642 km was covered in 3hr. 52min. This represents an average speed in excess of 100 mph over a distance of 400 miles. No train in the world has ever travelled so far so fast on track not specifically built for high speed running.


Passenger carrying in 1984 started with members of BR staff - and their families - travelling in their own time, followed by the entry into regular public service in the summer. The opportunity was taken to commission consultants to carry out surveys of travellers' attitudes and reactions - with encouraging results. Highlights of the analysis of the surveys are:-

Respondents who had travelled on other InterCity trains during the previous six months were asked to rank their assessment of APT compared with Mk3 coaches. Results showed that for the same route, APT provides a noticeable increase in smoothness and a most marked increase in comfort. It is significant that the results for the West Coast Main Line (WCML) are comparing APT at 200 km/hr with in the main experience of Mk3 at only 160 km/hr.

Passenger reaction to tilt was favourable. A majority stated that when seated they found the passage through curves more comfortable than in Mk3 coaches.

Finally, the so called nausea problem seems to have disappeared. Out of over 1000 respondents, only 15 made spontaneous mention of this subject with 5 saying that they attributed it to a lack of adequate fresh air - a feature which will be improved in the future by reducing the percentage of air to be recirculated. None of the 15 was sick and all felt better before the end of their journey which prompts the question - to what extent was the original reaction induced by the expectation that it would occur?

The APT-P based at Glasgow will continue to run three days a week between Glasgow and London. It will carry passengers on those days when demand warrants the extra capacity. Its programme after this time is totally dependent upon the development requirements of the IC225 vehicles currently being planned.


A second APT set (APT-D) has been based at Crewe and this is being used to carry out fundamental development work. The train ran some 25,000 miles in 1984 and all of the testing has been devoted to assessing the performance of a four axle (non articulated) version of the APT coach, a forerunner of the Mk4 coach. Although further work is planned for 1985 these tests have been most successful and have confirmed that it will be practical to provide a Mark 4 coach based on the APT concept as modified by the use of disc brakes and individual bogies.

APT-D will continue to be used as required for developments in conjunction with the IC225 (Class 91) locomotives and coaches.


If InterCity is to maintain its existing position on both of the West and East Coast routes - let alone improve it - the business has to make significant improvements to the product in the quickest time possible.

The key features are reduced journey times, better reliability and more comfort, backed up with cleaner trains and enhanced customer care. The first three items require new locomotives and coaches if any noticeable impact is to be made in the market.

Economics dictate that unit trains like APT or HST are no longer viable - the traction unit must be able to work, on average, over 20 hours every day hauling fast trains by day and freight or parcels by night. Thus the InterCity train of the future becomes a locomotive and an independent rake of coaches.

Studies completed during 1984 have shown that -

  1. for the West Coast Main Line - there is no financial benefit to be gained at running above 200 km/h. However, to be able to run at up to 9 deg. of cant deficiency does produce a good pay back. To achieve 9 deg. cant deficiency tilting coaches are a must.
  2. for the East Coast Main Line - whilst there is no clear financial benefit in running above 200 km/h, it is prudent to design for running at speeds up to 225 km/h in anticipation of future market requirements. The benefits of running at above 4.25 deg. of cant deficiency are only minimal between London and Leeds/Newcastle. There are, however, worthwhile journey time reductions to be had between Newcastle and Edinburgh but it is not yet clear as to whether the return from the market will support the additional costs of tilting coaches.
  3. the dichotomy in the coaching stock requirements between the West and East Coast routes suggests the adoption of a standard Mark 4 design which can be built in tilting or non-tilting versions. This will give lower costs through economies of scale.


A detailed technical study has been made into the feasibility of the Mark 4 coach and the results are very promising. Backed by the results of the passenger Comfort Tests carried out in 1983 and April 1984, this study is showing that, providing precedence tilt is used, it is quite acceptable from the passenger comfort point of view to travel at up to 9 deg. of cant deficiency on the West Coast Main Line with only 6 deg. of this compensated through tilting. This leads to the concept of a 6 deg. tilting coach which allows a larger and more attractive interior to be designed within the confines of the loading gauge.

APT is serving as an invaluable testing and proving bed for some of the systems for the next generation of InterCity traction and rolling stock. This will allow BR, in conjunction with industry, to introduce the new builds much more quickly than would otherwise be possible.

APT is being used to ensure that InterCity passengers will have a faster, more punctual and more reliable service which will take the form of IC225.

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Last Revised: 28.06.2022 10:44
by R G Latham
© 1998