Evaluating Operational Features of Multilane Turbo Roundabouts with an Entropy Method

Abstract

Traditional two-lane or multilane roundabouts gradually become less efficient and safer to operate with increasing traffic volumes due to the weaving area. To mitigate this problem, several new types of roundabouts, including the turbo roundabout, have been gradually invented. Turbo roundabouts have been widely used, attributing to their unique lane separation facilities which eliminate the weaving area and improve the operational efficiency and safety of the roundabouts. However, the most common turbo roundabouts are single-lane or two-lane ones with insufficient capacity. Therefore, this paper focuses on the operational features’ evaluation and forms selection of multilane turbo roundabouts using the entropy weight method (EWM). Based on the commonly utilized operational efficiency indicators, three additional indicators are selected to ensure the results’ accuracy. The EWM is innovatively used to calculate the weights of adopted indicators and achieve a comprehensive evaluation of different roundabouts under various traffic scenarios. Furthermore, the operational features of different roundabouts are simulated and analyzed in Verkehr in Staedten Simulation (VISSIM). The final results demonstrate the EWM’s utility in selecting optimal solutions. The spiral turbo roundabout showed the worst operational efficiency. The conventional form roundabout is proven suitable for small traffic volumes, whereas the rotor turbo roundabout performs better under large traffic volumes. In addition, a modified rotor turbo roundabout is presented, and the final results place its operational efficiency between those of the conventional form and the rotor. The turbo roundabouts achieve the most significant improvement in delays and the number of stops, potentially improving these aspects by more than 50%.