Analyzing the relationship between the efficiency and safety of a turbo roundabout by the factor analysis method

The construction of cities and economic development lead to more and more serious environmental pollution, and the concept of green and low-carbon city has been proposed. Therefore, a series of requirements have been put forward for transportation. CO and other pollutants will be produced in the exhaust of conventional fuel vehicles, which will seriously affect the urban environment, especially at intersections with large passenger and vehicle flows. When multiple roads, especially more than 4 roads, intersect on urban roads, traffic organization can usually be achieved by using a roundabout. However, due to the limited capacity of the conventional roundabout, with the rapid increase of the traffic volume, and there are many vehicles in the circle lane change and interweaving behavior. This has caused serious congestion at the roundabout, the significantly increase in pollutants emissions and the decline in air quality. As an unconventional design, the turbo roundabouts use canalized traffic to allowed drivers to select the appropriate lanes in advance depending on their destinations so that different lanes within the circle do not interfere with one another, which improves the safety of the intersection while ensuring capacity. The main purpose of this paper is to analyze the traffic efficiency and safety of the conventional roundabout scheme and turbo roundabout scheme for five-way intersections. Using VISSIM to simulate different forms of roundabout and analyzing the six selected evaluation indicators. The number of vehicles in different entrance lanes and the diameter of the circle are selected as sensitivity factors for sensitivity analysis. Finally, the factor analysis method (FAM) is used to classify the six indicators into two categories: traffic efficiency and traffic safety, so as to comprehensively evaluate the different schemes. The results show that the difference in performance between the two schemes was not significant at low traffic volumes. At high traffic volumes, the turbo roundabout was better than the conventional roundabout in terms of emissions, safety and throughput efficiency. CO emissions from vehicles on conventional roundabout are generally higher than those on turbo roundabout, up to 53.62%. Therefore, the turbo roundabout is more appropriate for heavy traffic conditions.