Formation of Spatiotemporal Traffic Patterns with Cellular Automaton Simulation

This study introduces a common unit (CU) of 1.25-meter×1.25-meter grid-cell and grid-site to respectively measure the vehicle sizes (in terms of cells) and to gauge the roadway spaces (in terms of sites). Generalized spatiotemporal definitions of occupancy, flow and speed of "cells" moving over "sites" and over "time-steps" are given to elucidate the collective behaviors of traffic flows. Deterministic and stochastic cellular automaton (CA) simulations are performed to explore the traffic patterns in two-lane context under pure and mixed traffic conditions. Vehicular space-time trajectories, flow-occupancy, speed-occupancy and speed-flow diagrams, and spatiotemporal traffic patterns associated with various safe gaps, with and without perturbation, are displayed. The simulation results reveal interesting traffic patterns with free flow, wide moving jam and synchronized flow phases.