. Railroad construction. Theory and practice . 81 55 23 .671 55 .369 24 .376 55 .207 25 .184 55 .101 26 (.46 1- 0 0 47 1 53 r 0 0 454 RAILROAD CONSTRUCTION. §425. According to it, 528° of curvature in one mile would increasethe expenses of each train passing over it by of theaverage cost of a train-mile, and according to the general prin-ciples laid down in § 421, 1° of central angle of any curve, nomatter what the radius, will increase the expenses by -^^ , or .0564% per degree. Therefore the cost per yearper daily train each way i
. Railroad construction. Theory and practice . 81 55 23 .671 55 .369 24 .376 55 .207 25 .184 55 .101 26 (.46 1- 0 0 47 1 53 r 0 0 454 RAILROAD CONSTRUCTION. §425. According to it, 528° of curvature in one mile would increasethe expenses of each train passing over it by of theaverage cost of a train-mile, and according to the general prin-ciples laid down in § 421, 1° of central angle of any curve, nomatter what the radius, will increase the expenses by -^^ , or .0564% per degree. Therefore the cost per yearper daily train each way is (at 95 c. per train-mile) 95 ) X 2X365= c. As a simple illustration (a more extended one will be givenlater), suppose that by using greater freedom •with regard toearthwork the crooked line sketched may be reduced to thesimple curve shown and a curvature of, say, 110° may be re-duced to, say, 60°. Note that since the extreme tangents are identical, the sav-ing in central angle results from the elimination of the reversed. Fig. 209. curvature and of that part of the direct curvature necessaryto balance the reversed curvature. Assume that there are sixdaily trains each way. Then the annual saidng is 50°:^$, § 426. CURVATURE 455 which at 5% would justify an expenditure of $ Ifthe extra cost of construction does not exceed this, the im-provement is justifiable, and is made all the more so if the proba-bilities are great that the future trafhc will largely exceed sixtrains per day. At the same time the warning regarding ^dis-counting the future with respect to expected traffic shouldnot be neglected. The possible effect of change of distancehas not been referred to in the above problem. In any case itis a distinct problem. According to the above sketch, thedifference in distance is probabl}^ very slight, and consider-ing the compensating character of extra distance, such smalldifferences may usually be disregarded. The possible effectof
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