A knowledge of intersection capacity is essential for appropriate evaluation and selection of alternative intersection treatments. Various methods are available to determine the capacity of intersections, the most popularamong them being the Highway Capacity Manual (HCM) method based on critical flow-to-capacity ratio. This study uses a comparable method of critical flows at an intersection to determine the capacity of conventional and non-conventional intersections. Called critical lane volume (CLV), this method approximates capacity as the sum of the critical flows at an intersection per lane. The critical lane volume method was used to develop a tool called Alternative Intersection Selection Tool (AIST) which estimates the capacity of alternative (innovative) intersections at peak traffic counts; this process allows researchers to ascertain the feasibility of variousintersection designs such as: conventional, displaced left-turn, restricted crossing, U-turn and median U-turn intersections. The AIST tool also calculates the capacity of one, two and three lane roundabouts using the HCMmethod. The AIST format shows the individual layout of select alternativeintersections and summarizes the critical lane volume computations, as well as other capacity measures. This paper briefly explains the method of using critical lane volumes for capacity calculation and exemplifies how the capacity was calculated for the various alternate intersections using the tool.
Abstract