Urban arterial roadways are one of the most important facilities provided for the public. To be beneficial, they should be designed to move high volumes of traffic safely at reasonable speeds and provide needed access to businesses and residences. This is the challenge roadway designers have before them. The ultimate goal of arterial design has been to develop a facility that will do all those things, do them well, and do them at a reasonable cost. The ideas presented in this paper suggest that this goal may be nearing fulfillment. The weak point of arterial design (or the linchpin, depending on the perspective) has been the arterial/arterial intersection. Extremely high volumes, both through and turning, come together at the same point at the same time, and all of these substantial traffic demands need to be served in the best manner we know how. Because of these conflicting needs, intersections have served as bottlenecks to the flow on arterial roadways, providing only 30-50% of the capacity available on the arterial itself. To improve arterial intersections, a widened intersection with turn lanes has typically been provided, controlled by a traffic signal. The alternative to this has been the consideration of a grade-separated interchange. For a congested arterial/arterial intersection, the at-grade solution has typically been too little, while the grade-separated solution has typically been too much. What follows is a concept that the authors hope practitioners see as a method for improving operational efficiency and utilizing untapped capacity on arterials.
Abstract