It is well known that the sharp curvature found on some of our east and west lines passing over the Allegheny Mountains has some effect in deterring travel from those lines. Women and children will grow "car-sick" while passing around some of these sharp curves at a comparatively high speed. But, on the other hand, a road which is so located usually has the compensation of attractive mountain scenery which may attract additional travel to an extent as great, if not greater, than the loss due to the crooked line. Again it must be considered that such an objection will only apply to a very small proportion of the competitive passenger traffic. The great bulk of the passenger traffic is unaffected while the freight traffic is absolutely unaffected. We are therefore justified in throwing this consideration out of account. Analogous to the above is the objection that a crooked line reduces the ability to make fast time and may deter travel on account of the apprehension of danger, but we may again consider, as above stated, that its effect is exceedingly small, and that whether small or large the general character of the country will absolutely prevent any change of plan which will materially affect the road in that respect. We are therefore justified in eliminating this phase of objections from our financial calculations.

In the chapter on Distance (§ 157) we have already considered the justification of a reduction of distance in order to save time on roads having a very large amount of competitive passenger traffic. On just such roads the reduction of even the rate of curvature assumes financial value. When express-trains are required to make an average speed, for considerable distances, of more than 60 miles per hour, the reduction of the rate of curvature becomes an important matter, since at such a speed the superelevation of the outer rail on curves of even moderate curvature becomes so high that it is objectionable, and the operation of such curves at high speed becomes dangerous. Even the nervous strain on the engineman, due to watching for clanger when rounding a sharp curve at very high speed, cannot be ignored, and on this account many railroads will spend considerable money to increase the radius of curvature, even though they are unable to reduce the number of degrees of central angle; but all these considerations apply only to that very limited portion of the traffic on a very small percentage of the total railroad mileage. Very few engineers ever have occasion to consider such cases.

162. Effect Of Curvature On The Operation Of Trains

It is true that curvature does increase the resistance to traction and that uncompensated curvature, when located on a ruling grade, virtually adds to the rate of that grade, and therefore might have a limiting effect on the length of trains which would prove very serious. This, however, can almost always be avoided by compensation for curvature. There are a few very rare cases, of which the Hudson River Railroad is the most conspicuous example, in which the general grade of the road for many miles is almost level, and yet where, on account of the rocky bluffs on the river-bank, sharp curvature is unavoidable, except by enormous expenditure. In such a case curvature may actually have a limiting effect on the length of trains, but such an exception is so very rare that it need not in general be considered.

Limiting The Use Of Heavy Engines

It has been asserted that very sharp curvature will prevent the use of the heaviest types of engines. While such an objection will probably have some force, if applied to abnormally sharp curvature, such as 18° or 20° curves, it hardly has any force for curves which are even as sharp as 10° curves. The "consolidation" engine was originally designed for use on the sharp curves and steep grades of the mountain division of the Lehigh Valley Railroad. It has even been claimed as the result of tests that the consolidation engine has less resistance per ton on sharp curves than an engine of the "American" type. Although these tests have been subject to question regarding their accuracy, it is quite evident that they were sufficiently accurate to prove that sharp curvature does not prevent the use of heavy engines or even make an abnormal reduction in their efficiency on sharp curves.

We therefore reach the only rational objection to curvature which may be directly computed in dollars and cents, and that is the increase in operating expenses.