When a train moves with speed, a certain resistance develops due to the wave action of the train. Similarly, track irregularities such as longitudinal unevenness and differences in cross levels also offer resistance to a moving train. Such
resistances are different for different speeds. There is no method for the precise calculation of these resistances but the following formula has been evolved based on experience:
R2 = 0.00008 WV (25.2)
where R2 is the resistance due to wave action and track irregularities on account of the speed of the train, W is the weight of the train in tonnes, and V is the speed of the train in km/h.