2.813 63 270 cont Average cost pile of side track in per cent of man track 107 279 15.60 260 85 120 457 16.24 242 .94 138 677 9.61 215 1.42 106 167 11.06 380 .57 formula will give the average expense to maintain due solely to age and decay for the accounts where both decay and mechanical wear enter the question and using the tabular values for the functions as deduced from these statistics for 1911 the average expense for any volume of traffic per mile of main track can be estimated: A Total Main Track Mileage. B Total Side Track Mileage. C P X Average annual charge to the given account. Proportional charge per mile of side track as compared with charge for main track only. Annual charge per mile of main track to keep in condition for proper operation covering the amount due to age or decay. R Proportion of X representing the additional charge per mile of main track for each million equivalent ton miles per annum. M = Million ton miles traffic per annum per mile of main track. E = Charge per annum per mile of main track only, for the given The values given for P and R in the tables with conclusions are suitable to determine average value of X for the great bulk of the railroads of the country, providing a sufficient number of years' data is used to produce a normal average. For the exceptional cases where a large portion of total track mileage consists of busy industry spurs and sidings, suitable values for P must be ascertained. The data given for ties is based on a study of renewals on different divisions of the same line with widely varying traffic. On track where ties were of a high grade timber or creosoted and with a large proportion of ties protected by heavy tie plates, the renewals in main track were 6.5 per cent. of total in the track plus 0.3 per cent. for each million equivalent ton miles traffic. This figure appears to fit very closely the northern half of the United States where the roads have taken means to properly protect the ties. In the southern portion the per cent. due to decay will be greater, but by multiplying the proper percentage by the value .046 per million equivalent ton miles, the average renewals can be approximated for cases where proper methods are used to retard mechanical wear. Each locality can determine within reasonable limits the value of the constant renewals required due to decay for the available timbers. Account 4, Rail Renewals, apparently costs about $11.00 per mile of main track for each million ton miles and requires about 1.1 tons of new rail for this traffic. This figure will answer under present conditions of rail renewals and checks very closely with some data gathered on the equivalent ton mileage per mile of track during the life of 80-lb. tangent rail on a busy double track division. The maximum equivalent tons over any of the rail was 147 millions. The tangent rail released was in condition for relayers or for re-rolling and considering 110 million miles the average for this rail would make practically 1.1 tons per million equivalent ton miles. According to custom the maintenance charges are only for the weight released less the arbitrary credit for the usable released material, although heavier section may be used for replacements. The relayers when used to replace still lighter section on districts of less traffic will further reduce the maintenance charge, as the rail finally released fixes the final distribution of total cost between Maintenance and Betterments. It is apparent that as the average weight of rail approaches the modern heavier section that betterments will absorb a less proportion of expense of rail renewals and maintenance charges will be increased. Sufficient data is not at hand to show whether the heavier rail will withstand an equivalent increase in tonnage directly proportional to its weight. It can hardly be expected to do so as head wear determines the necessity of renewals where rail sections are sufficiently stiff for the axle loads. The cost of rail renewals will probably be found to bear a different relation to volume of traffic in a very few years. The other Maintenance of Way and Structures accounts affecting main track are for all practical purposes independent of the volume of traffic. Most of them are dependent on either mileage of main track or mileage of road. Tunnels, Bridges and Culverts and Over and Under Grade Crossings are dependent on topography of the country and materials of construction and in comparing the relative economy of different locations the amount and character of tunnels and bridges on each must be considered in estimating the difference in maintenance costs. The tables in the conclusions give the accounts under their respective headings. Other Maintenance of Way and Structures accounts may be ignored as they bear practically no relation to location. Average values for any of these main accounts can be obtained from Interstate Commerce Commission Reports for the leading roads in all sections of the country. The foregoing covers only the foundation of the work for analyzing the effect of changes in physical characteristics on Maintenance of Way and Structures accounts. It can be seen that distance affects nearly all of the accounts mentioned and that volume of traffic affects only a portion of them. Curvature affects only the rail renewals and roadway and track accounts with a very slight addition to tie renewals, providing that good substantial tie plates having large bearing area are used. It must be assumed that proper details of construction are used in the initial work in estimating relative values of different lines. Future study of the Cornmittee should be to determine the effect of curvature on the accounts mentioned and then take up the study with reference to Maintenance of Equipment and Conducting Transportation expenses. The following are the conclusions with reference to the present study: CONCLUSIONS. Maintenance of Way and Structures: 1. The problems of economic location deal only with main track in the majority of cases, side tracks entering into the question only where differences in distance is so great as to necessitate additional side tracks. 2. The annual charge per mile of main track for any account embracing both main and side track can be approximated for any operated line by the following formula : A=Total average main track mileage. B= Total average side track mileage. C= Average annual charge to the account. P=Proportional charge per mile of side track as compared with charge per mile of main track. E= Average annual charge per mile of main track only. The average value of P is shown in the table, but for roads located almost wholly within dense mining or manufacturing districts requiring an exceedingly large proportion of busy side and spur tracks the values would be higher and should be determined. 3. The accounts covering maintenance of main track do not all vary by the same general law, but vary most directly according to the following groups: (a) Affected by both miles of track and volume of traffic. (b) Affected by miles of main track. (c) Affected by miles of road. (d) Affected by local topographical features. Therefore no single unit of measurement of relative maintenance expense is applicable to all accounts in comparing the relative economies of two locations. The tables show the groupings of the accounts under their proper heading. 4. One ton of passenger train does more damage to track than one ton of freight train and the locomotive creates more disturbance than an equal weight of cars and contents. Until data is available to correctly estimate the relative damage, it is recommended that the following ratio' be used in estimating effect of traffic on the accounts in Group (a): One ton of passenger car and contents produces approximately the effect of two tons of freight car and contents. One ton of locomotive produces approximately the effect of two tons of the balance of its train. The total ton mileage reduced to terms of ton miles of freight car and contents is termed the equivalent ton mileage. Most of the accounts in Group (a) have a constant maintenance expense due to age and decay plus an additional expense depending on volume of traffic. This additional expense per mile of main track varies most directly with the equivalent ton mile. The equivalent ton mileage can be approximated by adding together the following: Net freight ton mileage. Double the freight locomotive mileage times average weight in tons. Freight train car mileage times the average weight of empty cars (at present about 18 tons). Double the passenger train car mileage times the average weight of car and contents (at present about 44 tons). Four times the passenger engine mileage times the average weight in tons. 5. The average annual expense per mile of main track due to age or decay for the accounts in which this item enters can be approximated for any road by the following formula: E=Charge per annum per mile of main track only, X=Annual charge per mile of main track due to age or decay. E=X+MRX = X (1 + MR) X: C C A+ BP = A+ BPMR (A + BP) Average values for P and R are shown in the tables. ACCOUNTS AFFECTED BY MILES OF TRACK AND VOLUME OF TRAFFIC. |