ABSTRACT
Consider a supplier of transport services (railway operator, ferry, airline, transport firm) between locations A and B. In many cases demand in both directions is not balanced: the demand for freight transport between A and B may be quite different from that between B and A. For passenger transport, a balance usually exists at the aggregate level of 24 hours, but when we take into account shorter periods again disequilibria may exist. For example, during the morning peak many people travel from suburbs to the centre of the city, but in the reverse direction the trains are almost empty.
