Modified Adjustment Factors in Estimating Capacity for Modern Roundabouts

This article is concerned with the development of adjustment factors that can be applied to the capacity estimation of modem roundabouts, which have not yet been introduced in Korea. There are two main model approaches that estimate the capacity at modern roundabouts throughout the world, namely, empirical statistical models and theoretical models. The formula in this paper adopts the basic structure of the 2000 HCM model, a notable theoretical model initially developed by gap acceptance theory. However, the formula proffered in this paper takes into account equivalent adjustment factors for consistency and homogeneity assumptions made in the original formula. In addition, another adjustment factor for approach grades at roundabouts is also introduced. Thus, the HCM formula is gradually enhanced with the adjustment factors developed in this paper. Some computational efforts are made for the validity of equivalent adjustment factors.