The object of introducing a transition curve at each end of the circular curve is
[A].
to obtain a gradual increase of curvature from zero at the tangent point to the specified quantity at the junction of the transition curve with the circular curve
[B].
to provide a satisfactory means of obtaining a gradual increase of super-elevation from zero on the tangent point to the specified amount on the main circular curve
[C].
to accomplish gradually the transition from the tangent to the circular curve and from the circular curve to the tangent
