Study On The Stability And Formation Mechanism Of Traffic Flow Under Urban Narrow Lane Environment

With the gradual shortage of urban traffic land,narrowing lanes has been paid more and more attention in traffic calming.However,most of the research on urban traffic flow theory in China focuses on roads with a lane width of 3.25 m and above.And theoretical studies of traffic flow in narrow lanes are still lack,which make the positive effects of narrow lanes doubtful and limit the implementation and application of narrow lanes.This study depends on Postgraduate Research & Practice Innovation Program of Jiangsu Province.This study takes a narrow lane of 2.8m wide as the main research object.The traffic flow characteristics are analyzed to provide a theoretical basis for the design of narrow lane.Firstly,this research starts with the characteristics of speed.By obtaining the spot speed of narrow lane and wide lane,the law of speed dispersion is analyzed.It is proved that narrow lane has a restraining effect on vehicle speed,thereby improving the stability of traffic flow.By obtaining free-flow speed in narrow lanes,K-S normal test and Homogeneity of variance test are used to analyze the distribution of freeflow speed.And on the basis of Highway Capacity Manual,a Gaussian function model of lane width and its free-flow speed reduction coefficient is established.Thus,the reduction coefficient of the free-flow speed under the condition of the lane width of2.8m is obtained.Secondly,this research starts with the phenomenon of staggered following under narrow lane.Through the definition of this phenomenon,the correlation analysis between its occurrence frequency and road density is carried out.Through the definition of this phenomenon,the correlation analysis between the frequency of staggered following and the road density proves that there is a strong correlation between them.In addition,the standard deviations of speed under different group forms are calculated,and their differences are proved by the Kruskal-Wallis test.The results show that the standard deviation of the vehicle speed is the smallest and the following state is the most stable when the vehicle is under the staggered following.In order to gain a deeper understanding of the car-following parameter law of staggered following,Person Correlation analysis is used to calculate the longitudinal gap of adjacent vehicles in staggered following group.It shows that the staggered following is the whole structure,and the vehicles in the group will restrict each other.Moreover,there is a certain linear relationship between the longitudinal gap,the lateral clearance and the speed between adjacent vehicles.The slope of the fitting function can be expressed by a linear regression equation,and the residual error can be corrected by the Burr distribution.Thirdly,this research starts with the trajectory of the vehicle.By collecting lateral clearance data of vehicles in different group states,and using mathematical statistical methods,it is confirmed that the selection of lateral clearance of vehicles is related to the psychological pressure of drivers.Under free-flow conditions,the appearance of high speed is usually accompanied by the situation where the vehicle is far away from the curb.And when the driver is driving on the left lane,the perception of the distance is more accurate,and the distance between the vehicle and the curb is relatively closer.In addition,the lateral vehicle will choose to be as far away as possible when a large vehicle passes by,so as to ensure that there is sufficient lateral clearance.This phenomenon provides a basis for the management of narrow lane,indicating that the 2.8m wide lane area cannot provide sufficient driving space for large vehicles.Finally,this research established a multinomial logistic regression model for the choice of car-following forms.It can simulate the driver’s selection of the following state according to the type of leading vehicle,the type of following vehicle,leader vehicle speed,speed difference of the following vehicle,lateral clearance,and longitudinal gap.The results show that different car-following parameters have different effects on the selection strategy of the car-following form.This model is helpful to the development of an autonomous driving model with narrow motor lanes.By identifying the operating state of the target vehicle and the interaction with surrounding vehicles,the appropriate form of following the vehicle can be selected.This research can enrich the traffic flow theory of narrow lanes.And it has practical significance for road design.