Roundabout Scenarios Research Articles

Simulation of the impact on carbon monoxide concentration resulting from replacing a signalised intersection with a roundabout

This work studies the impact of the substitution of a traffic light for a modern roundabout on carbon monoxide concentration. The estimate of CO concentration is made by means of the CAL3QHC dispersion model, considering only passenger vehicles as emitting sources. Local traffic and meteorological parameters had been adopted and the emission factors had been estimated using CMEM emission model. The maximum observed values in eight different wind directions had been compared, considering both moving and queued vehicles. The adopted model showed that the maximum concentrations of CO in the roundabout scenario were about 50% of the obtained values with the use of the signalised intersection. Concentration maps analysis demonstrated that not only the maximum values are higher in the case of the traffic light, but the area of the concentration curves is larger. These analyses are important for proper environmental management and contribute to traffic engineers seeking environmentally sustainable solutions.

A Stereo-Vision Based Object Tracking Approach at Roundabouts

This article presents a stereo-vision based system for the recognition of dangerous situations at roundabouts. To this end, we investigate the necessary field of view and viewing direction using videos taken by a panoramic camera. Using the insights of these tests, we build up a stereo-vision system. This system is based on the well established disparity estimation scheme semi-global matching and the recently introduced medium-level representation called Dynamic Stixel-World. This data is the input to compute a time-to-contact measure that makes explicit use of the roundabouts structural characteristics. This measure enables us to create a system for driver warning or possible automated intervention. Our empirical studies reveal that the warning decision correctly mimics human driver decisions in most roundabout scenarios.

Methodological Approach for Evaluation of Roundabout Performances through Microsimulation

In the literature, there are many methodologies that allow the evaluation of roundabout performances (Capacity, Levels Of Service, etc.): analytical models (HCM, HBS etc.), statistical models (TRRL, SETRA) etc. Each technique considers some aspects of the roundabout in comparison to others (geometric elements, vehicular flow and behavioral parameters). Obtained results are often not comparable among themselves because of distinctive peculiarities of each method. Today, the best way to solve this problem is by using a refined simulation software of vehicular circulation. However, along with a more and more refined analysis of microsimulation software algorithms, it is frequently necessary for each user (researcher, engineer, planner, etc.) to know the real sensitivity of these packages with regard to the most important key parameters. In this paper the Authors introduce the results of a wide survey conducted on an ample range of virtual roundabout scenarios by the use of a modern simulation software. Each scenario describes a fixed roundabout phenomenon using the following variables: geometric elements (inscribed circle radius, circulatory roadway, central and splitter islands etc.); characteristics of the traffic flow (dynamic traffic assignment, approach speed, circulatory speed and reduced speed zones, etc.); behavioral features (priority rules, minimum gap, minimum headway, etc.). The results are presented from the evaluation of stop-line delays.