The length of transition curve can be calculated by three conditions. ● Based on rate of change of centrifugal acceleration ● Based on rate of change of super elevation and extra widening ● Based in IRC empirical formula The length of transition curve depends on rate of change of centrifugal acceleration so if the radius of curve is infinity at the tangent point and hence centrifugal acceleration is zero. Similarly, at the straight end radius of curve has minimum value means centrifugal acceleration is maximum. hence, the rate of change of centrifugal acceleration should be adopted such that the design should not cause any discomfort to the drivers.