Diverging Diamond Interchange Analysis: Planning Tool

Abstract

Many traffic simulation software tools have emerged over the last decade and are widely used for analyzing capacity, delay, and level of service at intersections, ramps, and along arterial/freeway segments. Although these tools have shown great promise, they are expensive and the data collection and input setup is time consuming and resource intensive. Traffic engineers predominantly use one of those tools to analyze a diverging diamond interchange (DDI), also known as double crossover diamond interchange. Developing a simulation model and performing required analysis takes considerable time. Because it is not necessary to obtain a detailed traffic operational analysis of a DDI while interchange alternatives are being developed, a quick and easy evaluation procedure is warranted. In this paper, a critical lane volume (CLV)-based DDI analysis methodology is developed, which could be an appropriate tool to bridge the gap. In this methodology, two intersections or nodes of a DDI, where through-traffic movements along the arterial cross each other, are considered crucial. Understanding of the crossover movements, ramp movements, and coordination of traffic movements between the two nodes and lane configuration are used in developing the methodology. Critical movements are analyzed, compared, and logically added to obtain the CLV of the two nodes. The obtained CLV is used in deriving the level of service of the two intersections in a DDI. The paper describes the mathematical formulation and analysis procedure to evaluate a DDI. Two real-world DDIs are analyzed by using the developed method and compared with simulation results for reliability and accuracy.