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L. S. Rose, Chairman;
G. D. BROOKE, Vice-Chairman;
To the American Railway Engineering Association:
Of the seven subjects assigned to it the report of your Committee, submitted herewith for your consideration, covers the following:
(2) Methods for increasing the traffic capacity of a railway.
(4) Methods for analyzing costs for the solution of special problems with which this Committee is concerned.
(6) The economical operation of trains against the current of traffic on multiple track railroads.
(7) Begin the study of methods for the determination of proper allowances for maintenance of way expenses due to increased use and increased investment, collaborating with Committee on Records and Accounts.
The Committee has not been able to complete the work assigned to it, with the exception of Subject No. 6. This subject has been very fully covered by the Sub-Committee, with the assistance of the members of the Association. The report is contained in Appendix “D," with definite recommendations.
Considerable study has been given by a Sub-Committee to Subject No. 5, “The feasibility and economy of through routing of solid trains and its effect on the capacity of terminals,” but the Sub-Committee is unable to report this year. It is hoped that the result of the investigation of this subject will appear in the report of this Committee for the
Reports of Sub-Committees on Subjects 2, 3, 4 and 7 are contained in Appendices "A," "B" and "C.”
Attached as Appendix "E" is a report comparing the operation of one-engine and two-engine trains with three-engine trains, over the west end of the Cumberland Division of the Baltimore & Ohio Railroad.
The result of these tests is of some interest to operating officers having to operate mountain grades with heavy tonnage movements. The report was prepared by Mr. J. E. Teal, member of the Committee, and is published for the information of the Association.
ACTION RECOMMENDED 1. That the conclusions of the Committee given in Appendix D, relating to the economical operation of trains against the current of traffic on multiple track railways, be approved and published in the Manual.
Recommendations for Future Work The Committee recommends the reassignment of Subjects Nos. 2, 4, 5 and 7.
L. S. Rose, Chairman.
METHODS FOR INCREASING THE TRAFFIC CAPACITY
OF A RAILWAY
G. D. BROOKE, Chairman;
F. G. NICHOLSON, H. H. GARRIGUES,
J. L. WILKES, E. E. KIMBALL,
Sub-Committee. Last year the report of this Sub-Committee dealt in part with a few of the physical elements which more or less determine the capacity of a railroad. The discussion was largely academic and requires results of actual operations to prove its value. For this reason the Sub-Committee undertook to collect data on the physical characteristics of a number of different roads and the traffic which was being handled, for the purpose of noting to what extent the theory was applicable to practical operation. Replies to a questionnaire have been received covering the characteristics and operating data of 23 operating districts. Every case presents an interesting problem, but most of them are so complex that it has not been possible to show the application of the principles to each one.
It has, therefore, been decided to use one or two of the simpler cases which have been worked up to develop the theoretical discussion a step or two farther so that next year wider applications of the theory can be made. That is to say: Next year it is proposed to show the application of these principles to the economic development of a railroad taking into account the growth of traffic through various stages, requiring changes in motive power, additional running tracks, grade revision, signals, etc., and to attempt to show the effects of these changes upon capital expenditures and operating expenses.
NOTES ON THE DETERMINATION OF THE TRAFFIC CAPAC
ITY OF SINGLE AND MULTIPLE TRACK RAILWAYS
(SECOND PAPER) It was pointed out in the discussion last year that traffic capacity refers to the tonnage which can be moved regularly over a given arrangement of tracks in a given time. It depends on track capacity and operating methods. The latter are influenced by ruling grades, size of equipment, character of service, etc.
Track Capacity theoretically is fixed by the arrangement of tracks and passing sidings, and is measured in terms of train-hours per day (or month) per mile of line (or per division). It is based on the assumption that the arrangement of tracks is laid out for perfect operation and that full use is obtained of all passing sidings or other track facilities. In actual operation the arrangement of tracks is not always the best and it cannot be expected that train operations will be perfect, consequently full use will not be obtained from all of the passing sidings and track facilities. The use which can be obtained in practice from given track facilities depends upon the character of service and no doubt varies with different roads having different methods of operation. It will be difficult to find identical conditions on any two roads, consequently the results obtained from one road may not be applicable to another, but if the actual use obtained from given track facilities or the actual track capacity determined by different railroads is compared with the theoretical track capacity, a useful criterion can no doubt be established which will be valuable in deciding when it will be most economical to provide new facilities.
This year, profiles, track layouts and operating statistics were obtained from a number of different railroads having busy single and double track sections. The Committee has been unable to work up enough of this data to draw final conclusions, but the methods of attack are no doubt instructive, and possibly if some of the roads which are faced with the necessity of installing new track facilities can apply some of the principles discussed to their problems, valuable conclusions can be drawn therefrom. Determination of Theoretical Track Capacity.
Probably the best way to explain what is meant by the theoretical track capacity of a line is to consider Divisions A, B, C and D, Fig. 1. Divisions A and B are essentially single track lines having 24 and 21 passing sidings between the ends of the double track sections, respectively. There are 25 and 22 stretches of single track between terminals, or one more than the number of passing sidings. (Lap sidings for the present are counted as one.) To obtain the theoretical track capacities of these divisions assume that the sidings are located so that perfect operation is possible, that all trains make the same speed and that full use can be made of all passing tracks. Thus the theoretical track capacities of the single track sections of Divisions A and B are 25 X 24 = 600 and 22 X 24 = 528 train-hours per day, respectively. (See page 745, Proceedings A.R.E.A., Vol. 22, 1921.) It is also essential to assume that the passing sidings are long enough to accommodate but one train. If it is found by comparing the average length of sidings with the average length of train that the sidings are twice as long as the trains, or if there are lap sidings, then the theoretical track capacity is equal to twice the values found above. That is, it will be possible to accommodate two trains in each siding and thereby be able to operate trains in fleets. This is equivalent to installing passing sidings half the distance apart. (See last year's report.)
Thus, to arrive at the theoretical track capacity of a single track line in train-hours, divide the total length of passing sidings by the length of train it is proposed to operate to obtain the equivalent number of intermediate sidings. Increase this number by one and multiply by 24 to obtain the total train-hours per day for the division.
Divisions C and D include some double track. If the length of double track plus the length of sidings does not exceed 50 per cent of the length of the division it is possible to find the theoretical track capacity in the same manner, assuming the second track is split up into sidings equal to the length of trains and distributed throughout the division.
If the length of double track plus the length of sidings is more than half the length of the division, we have assumed that the theoretical track capacity will be expressed in terms of the double track capacity estimating the double track capacity on the basis of trains one train length apart on each track. (See page 745, Proceedings A.R.E.A., Vol. 22, 1921.) That is, the theoretical double track capacity in train-hours is equal to 12 times the number of tracks times the miles of second track and sidings divided by the length of train expressed in miles. On double track sections minimum train spacings may be determined by block signals, in which case the rule should be changed and length of block section substituted for length of train.
Table I gives details of operating statistics necessary for estimating the theoretical track capacity. Determination of Actual Track Capacity.
When a road reaches the point where train movements are seriously interfered with on account of limited track facilities, we will assume the conditions then existing represent the actual track capacity of the division. The period of greatest movement can then be selected and analyzed to establish a measure of the actual track capacity. Obviously in the beginning a road must have reached this point before its actual track capacity can be determined. When the actual track capacity has been established for a number of different roads it is felt that it will be possible to determine certain criteria and relationships between various factors of train operations which will make it possible to forecast the actual capacity of similar roads before they reach the limit of their present facilities.
The actual track capacity will be very much less than the theoretical for the reason that we have elected to base the theoretical track capacity on the most favorable conditions. In practice, conditions must be taken as we find them. Trains do not run at a uniform speed, passenger trains and freight trains run at different speeds, and when the two services are maintained there will be more or less interference of one with the other, tending to restrict the time when the running tracks can be used.
Furthermore, due to the fact that passing sidings are laid out so that the running time is not uniform between all sidings, it is impossible to obtain full use from all of the track facilities. The section which takes the longest time for a train to run over it in both directions determines the number of trains which can be operated over the division. It will thus be seen that the actual track capacity can often be improved by a rearrangement of sidings.