be eliminated, and they must be connected by a curve. The length of the curve depends upon the
size of the angle and the length of trains traveling over the line. Figure 1.5 illustrates why long
trains and sharp angles require long vertical curves.
Figure 1.5. Need for Vertical Curves.
The gage of a railroad, as figure 1.6
shows, is the distance between the rails. It is
measured at the gage line, that is, between
points five-eighths of an inch from the top
inside of the rails and at right angles to
them. Cars and locomotives can move over
tracks only if their gages match. In the
United States, standard gage is 56 1/2
The following subparagraphs discuss
the terms applied to the sides of a rail, the
Figure 1.6. Rail Gage.