Headway

High Speed Multiple Units

Push-Pull Operation

Push-pull operation was really only an adaption of the multiple unit principle but applied to a locomotive powered train. Assuming a regular level of traffic and an even interval service was required, trains could be formed with a locomotive at one end and a driving cab on the coach at the other end. If you could find a way of doing it cheaply by converting existing coaches, it could represent a big step forward.

The idea has now been adopted world-wide in two forms. One, as stated above, uses a locomotive at one end and a coach equipped with a driver's cab at the other end. The number of vehicles in between them may be varied seasonally if required but the formation is not normally varied on a train by train basis. In the UK, the coach at the rear has become designated a Driving Van Trailer (DVT). It is used to carry luggage and passengers are not permitted to ride in it at speeds over 160 km/h.

The second push-pull form uses two locomotives, one at each end of the train. This was applied to the Channel Tunnel "Le Shuttle" trains and has also appeared elsewhere, notably in Taiwan. The two locomotives are necessary in these cases to provide sufficient power.

The modern two-locomotive concept for push-pull operation first appeared in 1959 with the UK's Blue Pullman series of trains. A diesel power car was provided at each end of a six- or eight-coach set. The concept was further developed in the 1970s with the UK High Speed Train (known as the HST) and in France with the TGV (Train à Grande Vitesse). The former is diesel powered, the latter electric but the concept is the same. Both these trains employ a power unit at each end with a set of passenger carrying coaches in-between. The Germans have joined the club with their ICE train. The only real difference between these trains and the original push-pull concept is that the newer trains were purpose built.

Not forgetting the Japanese high speed train concept; they were the first to introduce over 200 km/h running on a regular basis and have kept at the forefront of high speed train technology with their German and French counterparts. However, the Japanese HSTs have always been multiple units in the original sense, having many power cars distributed along the train.

The HST name was first used for diesel multiple unit passenger train developed in the UK for 125m/hr running. It is now generally accepted as the definition for any passenger train scheduled to run at over 200 km/h.

This is the name given to the elapsed time between trains passing a fixed point in the same direction over the same track. It is usually expressed in minutes e.g. "trains were running at a 4-minute headway (укр. – інтервал між поїздами)". Another way of expressing it is as trains per hour (tph).

A well run railway will conduct research to determine how many fare paying customers are likely to show up at various times of the day and will operate their trains to suit.

In many instances the patronage numbers will show that it is possible to run trains at even intervals or at a given "headway". This may be at two hours for a long distance, main line route or two minutes for a metro.

Once established, the headway is used in calculating the number of trains required for a particular service, the train performance requirements and signalling requirements.

Дата добавления: 2014-01-11