Turbo-Roundabout: Case Study of Driver Behavior and Kinematic Parameters of Light and Heavy Vehicles

Abstract

This research compared kinematic and behavior parameters of light and heavy vehicles at turbo-roundabouts. This is of interest because heavy vehicles can influence turbo-roundabout functionality more than that of conventional roundabouts. The traffic arrival process at arms of a typical turbo-roundabout was studied. Using image-processing techniques, the trajectories of about 1,400 light vehicles and 300 heavy vehicles were examined at a roundabout entry, on the ring, and at the roundabout exit. Light vehicles had moderate average speeds lower than 25 km/h at the entry lanes, 15 m prior of the yield line, whereas heavy vehicles had an average speed of about 20 km/h on the same section. Significant differences were found in average acceleration: they were generally below 2 m/s2 on arm lanes and 1.5 m/s2 on circulating lanes for light vehicles, whereas those of heavy vehicles were 0.5 m/s2, much lower than the corresponding acceleration values of light vehicles. The values of the critical gap tc and follow-up time tf estimated for light vehicles ranged between tc=4.03−5.48 s and tf=2.52–2.71 s respectively, whereas heavy vehicles had tc and tf values 15%–47% higher than those of light vehicles.