Average Speed Control and Energy Conservation on Limited-Access Highways

Cynthia M. Bruso
J. Richard Shanebrook

DOI: 10.2190/3WJK-7PQJ-K5NQ-079A


A system for average speed control on limited-access highways for the purpose of conserving energy is presented. The system is particularly well-suited for toll roads where times of entry and exit can be recorded and used to determine the average speed maintained by a vehicle between the entry and exit locations. Estimates of the amount of fuel that can be saved by strict adherence to a given speed limit are determined by accounting for the aerodynamic drag and rolling resistance forces that act on a vehicle during constant speed motion. Using available data for average speeds and total mileage travelled on the New York State Thruway, it is estimated that between 12.7 million and 33.7 million gallons of fuel could be saved yearly by Thruway motorists if they all adhered to the national speed limit of 55 mph.

The paper concludes with a brief discussion of the safety benefits of a system of average speed control. It is anticipated that fewer vehicle accidents would occur due to the smoothing and slowing of the flow of traffic.

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