Gathering the necessary information required to tackle traffic congestion problems is generally time consuming and challenging but is an important part of city planners’ work. The purpose of this paper is to describe the methodology used when analyzing potential solutions for the Arizona State Route 89A and Highway 179 roundabout in Sedona, Arizona; which is currently experiencing significant congestion. The oversaturated condition is typically applied to signalized intersections but its application to roundabouts requires further exploration for future management of similar transportation systems. The accompanying Quick Estimation and Simulation model (QESM) spreadsheet was calibrated using an iterative process to optimize its level of adaptability to various scenarios. This microsimulation modeling program can be used to predict the outcome of possible roadway improvements aimed at decreasing traffic congestion. The information provided in this paper helps users understand traffic system problems, as a primary to visual simulation programs.