Analysis of vehicle trajectory characteristics on small radius ramps of freeway interchanges
Unmanned aerial vehicles were used to take high-altitude photographs over two highway interchanges in Sichuan province to clarify the vehicle trajectory characteristics and driving modes on small radius ramps of highway interchanges via collecting trajec-tory data,speed,and trajectory coordinates of vehicles traveling on small radius ramps by video analysis method.By analyzing the relationship between driving trajectory and lane occupancy,the relationship between the trajectories of different vehicle models and different driving stages was obtained.The different driving trajectory preferences under different small radius ramps were clarified,and the effect of operating speed on the driving trajectories of different types of vehicles was analyzed.Additionally,the trajectory curvature was calculated using the three-point positioning method,and the curvature characteristics of small radius ramps were ana-lyzed.The difference between trajectory curvature and ramp curvature,as well as the trajectory lateral characteristics,was deter-mined.The research results indicate that among vehicles traveling on ramps,small and medium-sized buses have wider trajectory harnesses on the gentle curve section of small radius ramps compared to heavy vehicles,and their encroachment on lane markings is more pronounced on the circular curve section.The driving preferences of vehicles during the driving process are divided into three categories.It is found that on the A-type horn ramp,small buses and heavy vehicles with outer bends run at higher speeds,while on the diagonal quadrant double loop ramp,small buses with inner bends and normal heavy vehicles run at higher speeds.The overall curvature of the trajectory of small buses and heavy trucks on two small radius ramps is greater than the design curvature of the road.Both the amplitude and frequency of vehicle trajectory changes on diagonal quadrant double loop ramps are higher.
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