Abstract: Under different lane change intention,lane-changing behavior can be divided by their microscopic charac-teristics into free-flow lane-changing (FLC)and strained lane-changing (SLC).They are investigated through statistical a-nalysis methods based on NGSIM data in this paper.In order to ensure the accuracy of the data,the parameters for a sin-gle lane change behavior are extracted based on a data smoothing process,and spatiotemporal constraint rules,which are developed to eliminate abnormal samples.This paper uses regression analyses to study the significant influence factors of lane-changing durations of FLC and SLC,and develops a semi-logarithmic model to compare them.In addition,a polyno-mial model is developed to fit the lateral trajectory,and 3 variance indicators are selected to evaluate the optimal fitting order.The results indicate that the mean duration of SLC is slightly longer than FLC.Even though the durations are af-fected by distinct factors and weights,the lateral trajectories of SLC and FLC can be fitted with similar 5th order of poly-nomial models,and the goodness of fits are both greater than 0.99.