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The New Zealand Railways Magazine, Volume 1, Issue 2 (June, 1926)


Train diagrams are in general use throughout the world in connection with train running work. They are an essential part of the equipment of timetable offices. As it is probable that many members of the staff who have not been in touch with such offices are not acquainted with these graphs a reproduction of a train diagram for the Frankton-Ohakune Section is printed in this number.

The diagram is divided by vertical lines into 24 equal spaces representing the 24 hours of the day. Each of these 24 spaces may be sub-divided into spaces representing 30, 15, 5, or less minutes as found desirable.

The names of all stations where crossing loops are provided are shown at the sides of the train diagram in station order and at a distance from each other in proportion to the actual mileage between the stations. A horizontal line is drawn across opposite each station name.

The forms being ruled as shown, the next procedure is to insert lines to represent the trains. The timetable is taken and the trains are plotted on the diagram in timetable order.

Suppose that No. 115 Down Daylight Limited Auckland to Wellington is being dealt with. This train leaves Frankton at 10.22 a.m., Ohakune arrive 3.55 p.m. The line representing No. 115 commences at the horizontal line opposite Frankton and at the vertical line representing 10.22 a.m. It runs to Rukuhia 10.31 a.m. Te Kawa 11.5 Otorohanga 11.17 and so on to Ohakune, finishing at the intersection of the horizontal line opposite Ohakune and the vertical line at 3.55 p.m.

Similarly in the case of an up train, say No. 684 Up Daylight Limited Wellington to Auckland, the line for this train starts from the intersection of the Ohakune horizontal line and the vertical line at 3.22 p.m. Horopito 3.39 Kakahi 4.49 and so on to Frankton where it finishes at the intersection of the Frankton horizontal line and a vertical line representing 8.26 p.m. It will be observed that the line representing the down trains (odd numbers) run downwards while those representing the up trains (even numbers) run upwards, but both slope towards the right (the close of the day).

The lines denoting the trains must cross at one of the horizontal lines because these indicate the crossing sidings. In the few cases where the lines cross away from the horizontal lines the trains represented run on different days of the week and so do not cross. An example of this will be seen in the top left hand corner. No. 430 runs on Sunday only, and, as No. 243 does not run on Sunday, these trains do not cross.

The following are some of the points clearly shown by the train diagram:—

Whether trains are timed uniformly.

Where trains cross and where they pass. (No. 684 Up Daylight catches up and passes No. 244 at Te Kuiti at 7.15 p.m.).

Whether timed to follow each other too closely.

Whether times fit at crossing stations.

The density of the traffic on the section and at particular stations.

The hours staff are required to be on duty.

Where intermediate crossing places would be an advantage. (Note the long section between Poro-otarao and Puketutu.)

Where the work of a goods or mixed train requires regulation to avoid delay to a following fast train.

Connecting trains.

Where pick up or set down trains are provided. (No. 244 Taumarunui depart 4.15 p.m. is a pick up train for No. 684 Up Daylight as far as Te Kuiti. No. 413 Frankton depart 6.50 a.m. is a pick up train for No. 115 Down Daylight.)

It will be noticed that the section illustrated by this graph is occupied almost continuously during the whole 24 hours. The diagram gives a birds-eye view of the whole service on that particular portion of the line. It is very useful in arranging the runs of engines and trainmen. If a special train is required a glance at the diagram gives an indication as to where a clear track can be obtained. Any variation from the straight of a line denoting a train immediately catches the eye and indicates whether the train is travelling faster or slower than normal speed. Note the slowing up of the Down Daylight on the steep grade from Te Kuiti to Porootarao.

This class of work is a specialised one and considerable practice and experience is necessary to attain full efficiency. It is hoped that the diagram printed in this issue will stimulate interest in this branch of the work.

page 21
Train Diagram: Main Trunk-Frankton-Okahune

Train Diagram: Main Trunk-Frankton-Okahune