Models And Simulations Of Mixed Traffic Flow On Urban Roadways Under The Condition Of Carpooling Priority

With the development of population and the ownership of motor vehicles in metropolises, restricted road resourses are harder and harder to meet the exuberant travel demand of citizens. As a new mode of transportation, carpooling has been proved to be one of the effective means to ease congestion and to control traffic demand.In order to explore the practicability of implementing carpooling priority in our country, this paper modeled the mixed traffic flow on urban roadways under the condition of carpooling priority and analyzed the effectiveness of traffic flow based on cellular automata traffic theory. Then the assessment was executed considering fuel consumption and exhaust emission indexes under different traffic control measures on road section and different signal control measures at the intersection. The specific contents are as follow:(1) First, this paper detailed analyzed the factors influencing private carpooling and the implementation of carpooling priority, then it constructed an evaluation system of urban mixed traffic with indexes of traffic efficiency, fuel consumption and exhaust emissions. Besides, indexes of traffic efficiency include traffic volume, mean velocity, delay of vehicles and length of queue, etc.(2) Second, this paper focused on the car-following and lane-changing behaviors on road section and calculated the acceleration of the following car based on nonlinear stimulus-response theory. Then it modified the classic cellular automata model and proposed the Careful Driving Car-following model. The probability of free lane-changing was calculated considering types and velocity defference between the berore and the after vehicle. Then it constructed multi-lane cellular automata models of mixed traffic flow under different traffic control means such as having no priority lane, having a bus-only lane and having bus lane for both bus and carpooling cars. Based on this, it simulated and compared the traffic effiency under the refered three different traffic control measures on road section. Results show that having bus lane for both bus and carpooling cars have the best traffic efficiency.(3) Third, this paper detailed described the behavior of vehicles at different part of the signalized intersection and separated the intersection approach into three parts, such as the no lane-changing section, the frequently lane-changing section and the ordinary section. It derivated the probability of forced lane-changing considering turning demand and lane attribute of the vehicle and put forward the specific running rules for different flow in the weaving area. Then this paper constructed cellular automata model of the mixed traffic flow at different part of the signalized intersection. Based on this, it made a discussion on how to realize carpooling priority control for one single intersection and programed and simulated the mixed traffic flow at signalized intersection with red condensation carpooling priority signal. Results show that both traffic volume and mean velocity will increase when converted to carpooling priority signal control.(4) At last, this paper selected a road section north of Majialou in Jingkai Express Highway and Zhongguancun Street-Zhichun Road/Haidian South Road intersection in Beijing as examples to apply the cellular automata model of mixed traffic flow on urban roads and made simulation experiments. The simulation results show that it is close to the measured data. Then the models were applied to simulate the mixed traffic flow under the condition of carpooling priority and some evaluation indexes were calculated. Results show that, as for the road section in rush hour, when the carpooling rate is25%, traffic volume and mean velocity will separately increase1.49%and7.19%, mean fuel consumption and exhaust emission will separately decrease4.95%and4.47%if carpooling priority is implemented. As for the signalized intersection, traffic volume and mean velocity will separately increase4.33%and2.75%, mean length of queue and delay of vehicles will separately decrease14.88%and4.81%, mean fuel consumption and exhaust emission will separately decrease3.73%and3.98%if the carpooling priority is implemented.