IMPACT OF USING FREEWAY SHOULDERS AS TRAVEL LANES ON FUEL CONSUMPTION

A general procedure, based on data derived from the American Association of State Highway and Transportation Officials "Redbook", to compute the savings in fuel consumption that result from the use of low-cost conversions of urban freeway shoulders to travel lanes is presented. The data required for the analysis are traffic volumes, speeds, and vehicle classifications before and after the improvements. Three example projects are presented to illustrate the range of benefits in terms of total travel time and fuel consumption. The projects were implemented in Houston with three different objectives: relieve a main-lane freeway bottleneck, bypass a main-lane queue, and provide priority operation for high-occupancy vehicles (HOVs). The results of the study indicate that major improvements in traffic operations can be achieved from the additional capacity provided by the shoulder lanes. The magnitude of the improvements depends on the type of use of the lane, the geometric design, and the traffic conditions in the freeway section to be modified. In the three examples, the annual savings in fuel ranged from 187,875 gal for relieving a bottleneck to 7890 gal for bypassing main-lane queues to 3423 gal for HOV priority operations. The savings are the result of improvements in the average speeds of vehicles that use the modified sections. If the improvements can be related to a modal shift for the HOV priority operations, the savings are much greater. (Author)