Vehicle Movement Model And Stability Analysis Of Urban Expressway Curve

With the acceleration of urbanization in China and the continuous improvement of the people's living standards,the number of cars in our country has increased dramatically.The ever-increasing traffic volume has brought more and more pressure to urban roads.Traffic congestion not only has brought travel problems to people,but also caused great social and economic losses.Expressway,as the main road to ensure the normal operation of urban traffic,plays an important role in improving the operation efficiency of urban road network and shortening the regional travel time.As an important part of expressway,curved road has smaller curvature and lower stability than straight line because of its special linear design.It is a vulnerable section of traffic congestion and traffic accidents.Therefore,it is of great significance to strengthen the study of traffic congestion and traffic control simulation on curved roads and put forward the correct models and theories to reflect the traffic flow on curved roads.Firstly,the characteristics of curved road section are analyzed from four aspects: the type of curved road structure,the traffic characteristics of curved road,the driving stability of vehicles on curved road and the dynamics theory of curved road.Based on the dynamic characteristics of vehicles on curved road,the influence of lateral and longitudinal adjacent vehicles is analyzed,and the optimal speed following model is proposed.OV model of bicycle lane bend.By studying the expression of car-following model in curved road,and using perturbation equation and Fourier series convergence condition to analyze the linear stability of the model,the critical stability condition of car-following model in curved road is obtained.The factors such as bend radius,superelevation,lateral friction coefficient and the influence of adjacent vehicles on the car-following stability are studied.The resultsshow that under the same initial density of traffic flow,the stability of traffic flow in curved road increases with the increase of the leading vehicle influence coefficient,the stability of traffic flow in curved road decreases with the increase of adjacent vehicle influence coefficient,and the stability of traffic flow in curved road decreases with the increase of the radius of curved road.When the arc length and radius are fixed,the traffic flow stability decreases with the increase of lateral friction coefficient.Secondly,based on the study of vehicle lane-changing behavior and dynamic theory of corners,combined with the characteristics of vehicle lane-changing behavior,the minimum longitudinal safe distance model of two-lane corners is proposed.The three-dimensional relationship between the minimum longitudinal safety distance and the target vehicle's initial speed of lane change,the influence coefficient of adjacent vehicle's distance,and the three-dimensional curve between the minimum longitudinal safety distance and the target vehicle's initial speed and lane change time of lane change are plotted by using MATLAB.The lane change target vehicle and its adjacent vehicle are studied.The relationship between the minimum safety distance and the initial speed of the target vehicle,the influence coefficient of the adjacent vehicle distance and the lane changing time is analyzed.At last,the experiment of car-following in curved road is carried out by using artificial speed measurement method and artificial distance measurement method,and the measured data are processed.The relationship diagram of car speed and headway spacing in curved road is drawn by using the measured data.By comparing the measured results with the simulation results of car-following model in curved road,the simulation model is illustrated.The model can accurately reflect the car following characteristics of the actual curve road.Secondly,by means of high-point photography,the condition of turning isobserved and experimented,and the turning time and the turning distance of vehicles in the turning section are counted and processed.By comparing the measured data with the simulation result of the minimum longitudinal safe distance model of turning,the simulation model is proved to be more accurate.It reflects the lane changing characteristics of the actual curve roads.