Characterization Of Mixed Traffic Flow On Variable Speed Limit Sections Of Highways Involving Connected-Automated Vehicles

As the innovation driving force of the future automotive industry upgrading and an important part of the national innovation strategy,the Internet of Vehicles technology has received a number of policy support and assistance.At present,with the vigorous development of the Internet of Vehicles technology,it will be possible to control road traffic in the future through the integration of connected-automated vehicles and variable speed limit facilities.At the same time,due to the time required for vehicle upgrading,the mixed operation of manual-driving vehicles and connected-automated vehicles will exist for a long time in the future.Based on the above background,this paper intends to establish a microscopic traffic flow model close to this road situation and conduct a sensitivity analysis of different parameters through simulation to explore the impact of connected-automated vehicles and variable speed limit facilities on road traffic flow capacity,safety,and energy consumption.This will provide a reference for the regulation of speed limit value and the reasonable organization of vehicles in the future expressway variable speed limit sections.The main research work of this paper is as follows:(1)By distinguishing the driving characteristics of manual vehicles and driver characteristics of connected automated vehicles,this paper comprehensively considers the formation behavior of connected automated vehicles,the compliance status of two vehicle types passing through the speed limit section,and the different car following modes of vehicles,and proposes a new "manual-automatic" mixed traffic flow single lane cellular automaton model in the variable speed limit section of the expressway by combining the Gipps safe distance rule.Matlab is used to compile relevant programs and simulate them.The results show that the participation of connected automated vehicles can effectively alleviate the congestion caused by the low-speed limit and the phase separation caused by the interaction between vehicles,and improve the road flow.Under the variable speed limit control condition,the low-density road traffic is significantly affected by the dynamic variable speed limit value,and the trend of traffic change in the medium to high density area is closely related to the penetration rate of connected automated vehicles.In addition,when the penetration rate of connected automated vehicles is less than or equal to 0.4,the road flow is almost not affected by the variable speed limit control.When the permeability of connected automated vehicles is greater than or equal to 0.6,the change in road flow is positively correlated with the increase in dynamic speed limit value.In the case of the high-density roads with a 100 penetration rate of connected automated vehicles,the road capacity changes obviously with the maximum fleet length of connected automated vehicles Meanwhile,when the maximum platoon length of connected automated vehicles is greater than or equal to10 and the speed limit is adjusted to the conventional speed limit the average vehicle speed approaches the peak value of speed limit.(2)Considering the lane-changing behavior of vehicles and the V2 V communication function possessed by the connected-automated vehicles,,this paper introduces and improves the lane-changing rules for vehicles in order to further explore the road traffic potential.Combined with the established single-lane model,the lane is extended to two lanes to complete the construction of the two-lane model.To verify the advantages of the improved lane change rule,this paper compares and analyzes the lane change frequency,flow density diagram,spatial-temporal diagram,and speed fluctuation diagram before and after the improvement of the lane change rule through simulation.The results show that the improved lane-change rule has obvious advantages compared with the traditional STCA lane-change rule in the mixed traffic situation.Finally,on the basis of the established two-lane traffic flow model,combined with the congestion calculation formula,safety evaluation index,energy consumption index,and calculation rules,the congestion,safety,and energy consumption of the two-lane traffic flow model is studied.It is found that the congestion degree and safety of traffic flow are comprehensively affected by the penetration rate and speed limit value of connected-automated vehicles,and there is a certain change rule.The participation of a certain proportion of connected automated vehicles and reasonable speed limit setting has obvious effects on reducing road congestion degree and improving traffic flow safety.At the same time,the change in vehicle energy consumption decreases with the increase in the penetration rate of connected automated vehicles.Influenced by the speed limit value of the road section with variable speed limit and the driver’s compliance,the frequency and degree of the interaction between vehicles will change,and the range of vehicle speed will also fluctuate accordingly.