# Railway Engineering Questions and Answers – Vertical Curves and Realignment of Curves

This set of Basic Railway Engineering Questions and Answers focuses on “Vertical Curves and Realignment of Curves”.

1. What is formed when 2 different gradients meet?
a) Summit
b) Sag
c) Summit or Sag

Explanation: When 2 gradients meet an angle is formed at the point of contact. This angle formed is rough and can be smoothened by providing a curve called vertical curve which can be sag or summit curve.

2. Which of the following decides the length of Vertical curve?

Explanation: Length of vertical curve depends upon the Algebraic difference of gradients. It also depends on the type of vertical curve, whether the curve is of sag or summit type.

3. What should be the maximum rate of change of gradient in case of Summit curve?
a) 0.1%
b) 0.5%
c) 0.3%
d) 0.8%

Explanation: In case of summit curve the rate of change of gradient should not exceed 0.1% between successive 100ft chords. In case of sag it should be 0.05%.

4. Which of the following is the correct formula for finding the length of vertical curve for achieving maximum permissible speed?
a) L = a/r x 30.5m
b) L = r/a x 30.5m
c) L = a/r x 100m
d) L = r/a x 100m

Explanation: The length of vertical curve for achieving maximum permissible speed is given by the formula L = a/r x 30.5m. Here ‘a’ is the percentage algebraic difference between gradients.

5. Which of the following is not a major reason for the distortion of alignment of curve?
b) Horizontal forces on rail
c) Unbalanced forces on outer edge
d) Traffic from both sides

Explanation: A rail curve is distorted because of unbalanced loading due to cant deficiency or cant excess and horizontal forces exerted on rails. These horizontal forces make the curve flatter and sharper at various locations.

6. According to cumulative frequency diagrams when should the realignment take place?
a) Cumulative percentage of versines is negligible
b) Cumulative percentage of versines is between 10 and 50
c) Cumulative percentage of versines is less than 80
d) Cumulative percentage of versines is 100

Explanation: The versine variation on a 20m chord should be limited to 4 and 5mm for group A and B lines. Realignment should be taken up when the Cumulative percentage of versines which are lying within these limits is less than 80.

7. What should be the maximum station to station variation of versine on curves where speed in excess of 100kmph are permitted?
a) 15mm
b) 20mm
c) 30mm
d) 35mm

Explanation: Curves having speed permit of more than 100kmph should not have station to station variation of versines of more than 15mm. For speeds of 100kmph and less, this variation should not exceed 20mm.

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