Study On Lateral Acceleration Characteristics Of Interchange Ramp Based On Natural Driving

Interchange as an important road structure,makes the traffic in all directions run through different levels by the ramp.It reduces and eliminates conflict points,ensures traffic safety,thus,effectively improving the traffic capacity of the road.Relying on the National Natural Science Foundation of China and the Ministry of Transport's Applied Basic Research Project,this article takes three types of interchanges(loop,circuitous,and spiral)as the study targets,explores their lateral acceleration characteristics through natural driving experiments,in which 9 interchanges and 26 ramps were involved.At the same time,16 drivers of different occupations participated in this experiment and a large amount of natural driving data were obtained.By analyzing the lateral acceleration curve of cars on the ramp continuously,the author finds that the lateral acceleration of the loop and spiral ramps display a "three-phase" change: entering the growth phase,the stabilization or change phase,and exiting the deceleration phase.The second phase of the lateral acceleration of the loop and spiral ramp is mainly based on the “stability stage”,accounting for 41% and 53% respectively.Furthermore,the lateral accelerations of the circuitous ramp is characterized by a "five-stage" change: entering the stable phase,entering the growth phase,the stabilization or change phase,exiting the deceleration phase,and exiting the stabilization phase.Via the analysis of the driving path,lane selection and overtaking behavior of the car on the ramp,the author concludes that the car has the selection tendency of “inward inclination” and “inertial” driving habit when on loop and spiral ramps.The analysis also reflects that the car's selection of driving path on the ramp is closely related to the trajectory before and after the entrance of the lamp.The descriptive statistical analysis of the lateral acceleration of the loop and spiral ramps yields the statistical characteristics of the lateral acceleration under different conditions: the arithmetic average of the peak values of the lateral acceleration of the loop ramp and the 85% quantile are distributed at 1.62-3.02m/s2 and 2.12-3.61m/s2 respectively,and the lateral accelerations corresponding to the spiral ramp are respectively distributed at 2.07-3.08m/s2 and 2.54-3.67m/s2,in which the distribution frequency of the lateral acceleration of the loop ramp mainly displays “positive skewness”.Moreover,the distribution frequency of the lateral acceleration of the spiral ramp mainly shows a “negative skewness”;the position where the occurrence of second mutation of the cumulative frequency curve of lateral acceleration is mainly concentrated between the 92%-95% quantile.At the same time,by regarding lateral acceleration as a criterion for evaluating the comfort of the ramp,the author concludes that when the vehicle is used on these two types of ramps,the driver can all obtain a good driving and riding experience,and the feeling of “uncomfortable and unbearable” rarely occurs.The analysis of the relationship between "lateral acceleration-velocity" on the loop and spiral ramps reveals the differences in the "lateral acceleration-velocity" distribution between different ramps.The smaller the road width,the simpler the traffic environment.The more concentrated the lateral acceleration-velocity distribution.Furthermore,considering the aspects of comfort and speed,cluster analysis of “lateral acceleration-velocity” finds that it can be divided into three categories.This research provides scientific basis for the operation management,safety improvement,calculation model revision,and design specification revision of road interchange interchanges.It also promotes the development of safety evaluation theories and technologies for interchange.