OPERATIONAL AND ECONOMIC CONSIDERATIONS IN AN EVALUATION OF GEOMETRIC DESIGN ALTERNATIVES.

The discussion is based on recent research of driver behavior and a hypothetical analysis of level of service as related to invested capital. The relationship of speed characteristics on two-lane roads to overall geometric measures such as average curvature and hilliness and to traffic parameters such as volume and traffic composition was established. To increase safety and operational uniformity, consistent speeds should be the goal of designers. Based on a hypothetical logistic-type relationship between investment magnitude and level of service, suggestions were made for the level of service to be adopted for design purposes. Because of diminishing returns for a high level of service, an intermediate level of service may be desirable if purely economic considerations govern planners' decisions.