Enabling efficient transportation is a major challenge for large cities, as the transportation need is increasing, while the environmental impact has to be minimized. In this paper, we define an efficiency measure that shows how much of the current transportation mileage that is really necessary to meet all the transportation assignments. We show that the efficiency measure can be computed efficiently as a minimum cost flow, and we apply it on two case studies. The first case demonstrate the efficiency measure on a freight transportation system, and the second case computes the measure for a large real-world data set from the New York City taxis.