Other formats

    TEI XML file   ePub eBook file  

Connect

    mail icontwitter iconBlogspot iconrss icon

The New Zealand Railways Magazine, Volume 1, Issue 5 (September 24, 1926)

Modern Shunting Methods — Part IV.—Concentration and Marshalling Yards

page 24

Modern Shunting Methods
Part IV.—Concentration and Marshalling Yards

Definition.—These yards, as their title indicates, are constructed for the purposes of concentrating wagons converging from predetermined areas and directions; marshalling them into groups according to requirements; sorting them into order of destination, and finally despatching them to that destination.

A progressive country, such as this, is ever demanding more efficient and more expeditious rail transportation and it is incumbent upon us to see that we do not fail in meeting that demand. The introduction of more comprehensive statistics has enabled those responsible to gauge the position correctly and to show whether increased facilities are necessary and what economies would be effected by the installation of more modern methods. Until recently the traffic on New Zealand Railways has not been sufficiently dense to warrant the introduction of special shunting yards. The time has now arrived, however, when their construction in certain localities is justified, and two such yards are now being constructed, one at Middleton (Christchurch) in the South Island and one at Palmerston North in the North Island. It might be of interest, therefore, to discuss in some detail the general question of marshalling yards, their location, dimensions, general arrangement and the latest inventions for facilitating the shunting of wagons in modern yards.

Illustration 1.—English yard, showing main lines running through centre

Illustration 1.—English yard, showing main lines running through centre

Location.—The first and most important question to decide before planning a marshalling yard is “Where it is to be?” i.e., “Which is the most convenient point, having regard to traffic requirements, ground formation, land available, and other essentials?”

In the case of the two yards under construction, Palmerston North was not difficult to decide upon. Here is one of the main junction and concentration points of the North Island. It is growing in importance every year and one can safely assume that it will always remain an important junction and transhipping station whatever the change in the flow of traffic and whatever additional facilities may be provided at other junctions as the net-work of railways increases. Fortunately there is ample space at Palmerston North for this new yard and the natural formation of the ground lends itself to economic shunting operations.

The position of a marshalling yard to serve Lyttelton and Christchurch was, however, a more difficult proposition to decide. Accommodation was available at two points, one page 25 between Port Lyttelton and Christchurch and the other south of Christchurch. After investigation it was found that a yard on the main line south of the junction at Addington would be the most suitable.

Frankton Junction is obviously another point where, in the near future, a marshalling yard will be necessary.

Having decided on the location, geographically speaking, and taking it as an axiom that the yard must run parallel to the running lines, consideration must then be given to where the main line or lines should pass.

(1) Through the centre of the yard thus separating up and down traffic.

(2) To one side of the yard, if so, which side.

(3) Round the yard, that is in the case of duplicated main lines.

As regards No. 1 (through the centre of the yard) this is an expensive method which restricts flexibility in the use of shunting engines and staff and is only desirable where the traffic in one direction is independent of that in the other, or, where the movement is so continuous as to preclude any possibility of inter-change of engines and yard staff from one portion of the yard to the other, to meet fluctuations in traffic. If, however, there is a considerable “return” movement, constant inter-changing of wagons from one yard to the other has to take place over the main lines in order to get wagons on to trains going in the required direction, and if the yard happens to be the end of a Locomotive Division there is a possibility of considerable delay to train engines passing to and from the Loco. Depot. It frequently occurs, of course, that sufficient space is not obtainable to handle all the traffic on one side of the main line and the only solution then is to split the yard. In many cases it has been found more economical to free the main lines by building either “burrowing” or “fly over” junctions which enables communication to be made between the two yards without fouling the main lines.

Illustration 2.—A French yard, showing main lines to one side

Illustration 2.—A French yard, showing main lines to one side

Illustration 1 shows a yard with the main lines running through the centre.

As regards No. 2 (to one side of the yard) this is the most common practice and it has the advantage from the purely yard operating point of view of enabling closer supervision of the various co-ordinating movements and also permits of more flexibility of staff, and engines can be shifted at a moment's notice according to traffic requirements. Interference with the main line is reduced to a minimum if the yard is placed according to the Traffic Officer's recommendations. These recommendations must be based on data indicating the exact flow and nature of the traffic. Some of the matters to be considered are:—(1) In what direction or directions is the flow of goods traffic? (2) Periods over which maximum density of passenger and goods traffic is maintained (both directions separately) on all lines entering the yard? (3) How far does passenger traffic interfere with goods traffic at the period page 26 of maximum density of the latter? (4) Does the goods traffic in one direction require more sorting than in the other? (5) Are there more through or non stopping trains in one direction than in the other? (6) Does a change of train load or change of engine make it necessary for all trains in one direction to enter the yard? (7) Are there more stopping goods trains in one direction than in the other? (8) What is the position of the marshalling yard in relation to the nearest station yard, private sidings, junctions, etc.? (9) What is the position of loco, depot and wagon repair shops? (10) What is the length of “tablet” or “block” sections on each side of the yard.

In short, it is a question of deciding which side of the line will cause the least disturbance to main line operation. Where the main lines are duplicated and the flow of traffic in one direction is considerably in excess of that in the other direction, or the nature of the traffic is such that in one direction trains can more conveniently proceed to another yard further along the line, and that in the other direction numerous junctions, private sidings, etc., necessitate the splitting up of trains, the question of which side the yard shall be is easily determined. Unfortunately, however, it is rare in these days for the operating officers to be in the happy position of being able to decide the location of a yard from their point of view. Geographical and topographical features, the price of land and available space, etc., usually decide the issue. There is always the possibility, of course, of delay to main line traffic becoming acute by reason of the continual crossing over of trains arriving and leaving the yard. Where engineering difficulties do not prevent it, either the “burrowing” or “fly over” junction is then the only remedy, particularly where the main line is made up of four roads, i.e., two passenger and two goods. It might be argued that as regards
Illustration 3.—American yard, showing main lines running round each side

Illustration 3.—American yard, showing main lines running round each side

conditions here in New Zealand with single line operation it matters not which side of the line the yard is situated. It must not be forgotten, however, that single lines become double lines and that probably in the near future, for the presence of a new yard indicates more traffic and increased main line density. It is not only the present that must be catered for but the future. Illustration 2 shows a French yard on one side of the main lines.

No. 3 (round the yard, that is, in the case of duplicated lines). This is a practice most extensively used in America and has much to commend it particularly where a frequent passenger service is run either on the same roads as the goods trains or on separate fast traffic roads. As regards main line occupation the movements are all forward as all changes of traffic from one direction to the other is done in the yard. “Burrowing” and “fly over” junctions are avoided and the occupation of the main lines for goods traffic working in and out of the yard is reduced to a minimum.

In this type of yard a great deal depends on location. A modern yard can spread over three miles or more so that if the locality requires a station anywhere within the yard area separation of the main lines is not practicable. It is usually found that townships grow up around these yards and there is always a possibility of a station being required half way between the extreme ends of the yard. This together with the fact that expansion is usually limited are the only drawbacks in this type of layout, and are not really serious when one considers the economic advantages of having direct ingress and egress together with a complete “two direction yard” with absolute freedom of movement. The advantages, of course, are more outstanding when the traffic in one direction is dependent on the traffic in the other.