Vehicle speed profiles to minimize work and fuel consumption

This paper addresses the question of what speed profile will minimize fuel consumption of a land transport vehicle (road or rail) in traversing a path or route. Numerous previous Studies, using a control theory approach applied to specific profiles. have Suggested that fuel Consumption is approximately minimized by operation at constant speed. This result is derived much more directly here, along with boundaries on the conditions under which this result holds. The derivation relies on: (1) the approximate proportionality between fuel consumption and propulsive work; (2) the inherent resistance of a vehicle having the usual quadratic form (of road and rail vehicles): (3) the energy conversion characteristics of on-board gasoline or diesel (or diesel-electric) propulsion systems; and (4) relatively long distances between stops. Tests, using a train performance simulator, confirm the theoretical results. The results are discussed from the standpoint of basic principles in transportation engineering, and as guidance for designing systems that conserve fuel.