# Compound Curve

A compound curve (Fig. 13.14) is formed by the combination of two circular curves of different radii curving in the same direction. A common transition curve may be provided between the two circular curves of a compound curve. Assuming that such a connecting curve is to be traversed at a uniform speed, the length of the transition curve connecting the two circular curves can be obtained from the formula

L = 0.008 (Cal - Ca2) * V

or

L = 0.008 (C_{d1} - C_{d2}) x V_{m}, whichever is greater where C_{a1} and C_{d1} are the cant and cant deficiency for curve 1 and C_{a2} and C_{d2} are the cant and cant deficiency for curve 2 in millimetres. L is the length of the transition curve, in m,and V_{m} is the maximum permissible speed in km/h.