Underground Roundabouts: Analysis of Several Layouts for A Case Study in Urban Area

Background: Roundabouts eliminate some of the most complex and dangerous aspects of traditional at-grade road intersections. In recent times, novel two-level roundabout layouts have been proposed (i.e. target-roundabout and four-flyover roundabout). Nevertheless, no research on underground roundabouts is available. This paper analyzed the underground roundabout planned in the city of Trento (Italy). Objective: The paper examines an underground roundabout in an urban context, planned with the purpose of alleviating traffic congestion in the city of Trento (Italy). Four different layouts have been studied. Methods and Results: This study was conducted with the help of traffic microsimulation in the AIMSUN environment. The traffic model was calibrated using GEH index. The simulated queues are significantly close to the real queues measured in the year 2020. Conclusion: Underground roundabout can reduce queues, travel times, fuel consumption, air pollutant emissions etc. This particular type of roundabout could be used in urban contexts with a traffic demand and congestion problems comparable to those of the present study.