External combustion engines : prospects for vehicular application. Paper presented at the 51st Annual Meeting of the Highway Research Board HRB, Washington, D.C., January 1972.

External combustion engines as a possible alternative to the internal combustion engine for vehicle propulsion are discussed. It is pointed out that steam powered city buses give competitive road performance but they consume more fuel than diesel-powered buses do. Opportunities remain open for the evolutionary improvement of thermal efficiency.