Press Release November 1981

THE ADVANCED PASSENGER TRAIN (APT)

The Advanced Passenger Train is a high-performance, electric powered, energy-efficient train with tilting coaches for passenger comfort when the train traverses curves at speed.

It was designed by BR engineers and built by British Rail Engineering Limited to operate at speeds up to 125 mph and above on existing tracks and within the capacity of existing modern signalling to achieve journey time reductions of between 15 and 20 percent. Its capital cost and seat per mile cost compare favourably with other high-speed trains and slower trains of conventional design.

Why Do we Need an APT?

Average speeds and point-to-point journey times of most Inter-City trains in Britain are governed largely by the numerous permanent speed restrictions imposed primarily for passenger comfort on the many curves which abound the rail network. Approximately 50 per cent of BR's major routes is on curves.

To enable trains of conventional design to go round curves faster, tracks are canted - the outer rail raised above the level of the inner - but even with this technique, comparatively low speeds are necessary to ensure passenger comfort. As well as limiting journey times, the acceleration necessary after a speed restriction can be very costly in terms of fuel.

One solution - adopted in France for the Paris-Lyon route - is to build a new high speed route, but this is prohibitively expensive and well beyond the money and resources available to BR. Another would be to straighten out some of the most severe curves but this would gain only marginal improvements and still cost millions of pounds. And both solutions could involve land acquisition and lead to difficult environmental problems.

The most cost-effective solution is a train which can go round curves faster. This is the Advanced Passenger Train.

How does the APT achieve this?

APT has an entirely new suspension design which combines stable running and good ride quality in the train with low track wear. This allows shorter journey times to be achieved because it can take curves 20 to 40 per cent faster than conventional trains - including BR's High Speed Train - while ensuring passenger comfort by tilting the coach bodies inwards by up to nine degrees.

Efficient use of energy has been attained by lightweight construction, careful attention to streamlining the train's nose and tail profiles to reduce aerodynamic drag, and by achieving overall smoothness of the external surface.

How does APT compare with other high-speed trains?

Notes:

1. the TGV project, estimated to have cost about £800m so far, includes a new, double-track 410 Km highspeed rail route between Paris and Lyon. This is already two-thirds complete. The final section is due to open in 1983.
2. the APT trainset cost is that of a production series train.

How much has the APT Project cost?

This includes: research and development, an experimental train, three 14 car pre-production prototype trains, a maintenance depot at Glasgow, a part production line at Derby (BREL's Litchurch Lane Works); and modifications to the trains following the first phase of commissioning.

All-in-all an investment of under £3m a year since the project began.

Why has it taken so long to get the first APT into passenger service?

It took about seven years - from 1969 to 1976 - to move from the theoretical stage and the early research days through to the building and testing of an experimental APT. During this time many new components and systems had to be designed and exhaustively tested, and perhaps, modified several times even before they went into the make up of the experimental train. The next four years have been spent on designing, building and testing the prototype trains.

All this has taken place during a period of severe financial constraint and this, coupled with strict budgetary control, has required the APT to bear its full share of the economies called for from other sectors of BR.

It has not been possible, therefore, to provide at all times the level of resources - design, engineering and maintenance - needed to support the large volume of work entailed in testing and commissioning three full-length prototype trains. To some extent this aspect of the programme together with the time and resources needed to implement modifications was under-estimated.

More of the commissioning programme time was lost following the derailment of one of the trains. All test running was stopped until the cause - a wrongly assembled bogie - had been clearly established and all other bogies examined.

Altogether, these problems have added about two years to the commissioning programme.

What were the modifications?

Although the first 100,000 miles of test running proved beyond all doubt the fundamental soundness of the train's new technology, it was found that a smoother transition from straight to curved track could be obtained by modifying the coach tilt system to operate at an earlier stage than it had originally been designed to do. And although test running had shown that a tilt failure would be a rare occurrence, it was decided that it would be a sensible precaution to fit a device to lock a coach in the upright position in the event of a failure to avoid discomfort and unnecessary concern among those travelling in such a coach.

The most irritating problem encountered was with the train's conventional 'parking' brakes. The 'shoes' of these occasionally rub excessively on a wheel rim when the train is running and can cause an unacceptable build up of heat.

Because of this unsatisfactory characteristic (which is tolerable on trains with larger diameter wheels), a change in design will be adopted for the production trains. In the meantime the difficulty has been resolved by fitting a monitoring device which enables a faulty brake to be identified and isolated should this become necessary. This is allowing the trains to operate satisfactorily.

For high speed braking the APT is equipped with hydrokinetic (water turbine) brakes. These are giving excellent results and are proving highly efficient.

Is there a risk of collision with tilt failed coaches?

None whatsoever. The APT meets all the requirements for the safe operation of the railway laid down by the Secretary of State's Railway Inspectorate. There is no question of oncoming trains colliding if the tilt mechanism fails.

It has been reported that because of the delay to APT, BR is to build a 125 mph electric loco as a 'stop-gap' for the WMCL. What is the truth about this?

Even with a full fleet of APTs there will still be a need for a small number of 125 mph electric locomotives for use on routes and services for which it would be uneconomic to employ APTs. It is for this reason that a prototype is being considered. Because of the numerous curves on the West Coast Main Line only marginal journey time improvements over existing 100 mph trains would be gained by the employment of 125 mph electric locomotives on this route.

Why has the APT's speed been cut back to 125 mph?

The APT was designed to have a top speed of 155 mile/h (250 Km/h) and achieved 162 mile/h (260 Km/h) on one of its commissioning runs.

The market calls for competitive journey times and significantly improved journey time can be achieved without excessive energy consumption by operating at a maximum of 125 mph. At that top speed, for example, APT can cut almost an hour off today's best 5 hr 10 min journey time between London and Glasgow; reduce the 2 hr 30 min to Liverpool to 2.08 hours; and cut 24 mins off the 2.29 mins to Manchester.

The APTs proven 162 mile/h (260 Km/h) means that higher speeds can be called upon should the demand arise in future years.

Why have APT formations been shortened?

Although "self-contained" and with full catering services, the short length APT's to be used for the experimental passenger service between Glasgow and Euston, which begins on 7 December, are a temporary measure only. These will be increased to the planned 12 car trains when other 'rakes' of APT coaches have been worked up to the required standard for passenger service.

The original prototype train programme called for four trains, each with two 4,000 hp power cars. The two power cars were necessary to test the trains at their 155 mile/h (250 Km/h) design speed, and four trains were needed to sustain the proposed service of two trains a day each way between Euston and Glasgow. To save money it was decided to build only three trains and reduce the experimental passenger service to one journey each way between Glasgow and London.

How does APT fit into BR's Future Strategy?

It is to be the standard Inter-City train of the future dove-tailing in with plans to extend electrification to most of BR's main Inter City routes over the next 15-20 years.

Initially it is proposed to build 60 APTs for the already electrified West Coast Main Line - services between London and Glasgow, London and the Midlands and North West England, and between the Midlands and the North-West and Glasgow.

This calls for an investment of £186m for the 60 trains (£3.1m each) and about £100m for a production line, maintenance depots, and station works, much of which needs to be spent to replace life-expired assets.

What is the next stage in the Project?

To design the production series of APTs so as to be ready to start production when investment is given for the first 60 trains.

The most likely formation to be adopted for these will provide 496 seats (130 1st and 366 2nd and unclassified dining car seats), a driving power car at one end and a driving trailer car at the other, with full catering service.

This formation calls for a driving power car in which all the power equipment, at present housed in a vehicle the length of a passenger coach, has to be condensed to fit into a vehicle of the same length with a driving cab. This presents a big design effort at a time when BR's design resources are already stretched.

To enable production trains to be brought into service before the driving power car is ready, an interim measure is being studied which envisages using a separate power (of the type already designed) placed in the formation immediately next to one of the driving trailer cars.

APT-P

(2 + 12) Prototype Formation (534 seats)

SD3 - S2 - SC2 - U2 - F2 - FV3 - eP4 - eP4 - FV3 - F2 - U2 - SC2 - S2 - SD3

APT-P Formation

APT-R

(1 + 11) Interim Formation (496 seats)

DV4 - F3 - F2 - F2 - UC2 - S2 - S2 - S2 - S2 - S3 - eP4 - DA4

APT-R Formation

APT-S

(1 + 10) Series Formation (496 seats)

DV4 - F3 - F2 - F2 - UC2 - S2 - S2 - S2 - S2 - S3 - eDP4

APT-S Formation

Last Revised: 10.08.2022 17:45 by R G Latham © 2022