A REFINED PARSIMONY PROCEDURE TO INVESTIGATING NONLINEAR TRAFFIC DYNAMICS

Abstract

This paper refines the parsimony procedure developed by Lan et al. (2005) and revisits the nonlinear features of real-world traffic dynamics in different contexts. The refined procedure begins with filtering out the periodic and quasi-periodic patterns by Fourier power spectrum, then filtering out the equilibrium (fixed) points by largest Lyapunov exponent, and finally distinguishing chaoticity from stochasticity by iterated function system clumpiness maps between original and surrogate flow time series data. An empirical analysis of traffic flow data measured with various time intervals (20-second, one-minute, three-minute and nine-minute) during different times of day (midnight, morning, afternoon and evening) are examined. The results show that different nonlinear patterns may emerge or vanish, depending on the measured intervals and times of day. Traffic patterns in the morning (6:00 to 9:00 am) and evening (18:00 to 21:00 pm) periods are close to chaotic phenomena. During the afternoon off-peak period (12:00 to 15:00 pm), the pattern is close to stochastic phenomenon. The 20-second traffic pattern at midnight (0:00 to 3:00 am) is close to equilibrium point due to copious zero flows.