Correct Answer - Option 2 : Transition curve

**Explanation:**

**Transition curve:**

(i) To minimize discomfort arising out of the sudden change in curvature at the junction of a tangent and a curve, a special type of curve is provided in between for gradual change from the back tangent to the circular curve and again from the circular curve to the forward tangent. This horizontal curve having varying radius is known as the transition curve.

(ii) There are five objectives for providing transition curve and are given below:

- To introduce gradually the centrifugal force between the tangent point and the beginning of the circular curve.
- Gradual increase of super-elevation from zero at the junction of the transition curve with the main curve to the specified amount at the point of tangency.
- To provide a gradual introduction of extra widening.
- A
**gradual change of gradient from zero at the junction of the transition curve with the main curve to the specified amount at the point of tangency.**
**A ****gradual change of radius from some value at the junction of the transition curve with the main curve to the infinite value at the point of tangency.**