Method and system for deriving travel distance of a vehicle

A method and system of deriving a travel distance of an object which travels, comprising the steps of: measuring a forward travel velocity of the object under forward travel; discriminating whether or not the measured forward travel velocity is greater than a preset specified velocity; detecting a level of a backward travel signal indicative of a state of the object under backward travel, when the measured forward travel velocity is greater than the specified velocity; and calculating the travel distance of the object independently of the travel distance of the object in a case that a level of the backward travel signal differs from the detected level.