A methodology for estimating the incremental benefits/disbenefits and the benefit-cost ratio of changes in the total mix of transport services available. Benefits/disbenefits are compared along many dimensions from the viewpoints of users, operators, and the general public. An important distinction is made between primary demand (as for an intercity flight) and derived demand (travel to and from the airports). Freeway travel is considered a separate mode. Because of its straightforward additive features, the model can readily be extended to include classes of users, and perhaps a full network analysis can be formulated in a programming context. (An expanded version appears in RM-5869.) 29 pp. Ref.