SOME FINDINGS OF CA MODEL TO GENERATE VARIOUS FREEWAY TRAFFIC FLOWS WITH ADDITIONAL RULES

It's reported that real traffic flow has three phases such as free, synchronized, and stop-and-go flow, and that macroscopic flow-density relationship, called the fundamental diagram, has various features such as inverted V-shaped, inverted U-shaped, bell-shaped, reversed λ -shaped, and reversed λ - shaped with upward concave. Cellular Automata (CA) theory for microscopic vehicle simulation modeling is capable of simulating large traffic road networks faster than real time using both memory-saved and high-computing data structure. Although simplified CA models are able to robustly reproduce the basic properties of uninterrupted traffic flow, they have shortcomings to the description of some flow-density relation diagrams such as revered λ - shaped with upward concave and bell-shaped relation. Based on existent CA Car-following models, this paper proposes an improved CA model integrating two additional rules for both stopping maneuver in the tail of traffic jam and low acceleration within traffic jam. Consequently, the improved CA model describes microscopic vehicle behaviors such as braking maneuver at the tail of traffic jam and low acceleration within congested traffic flow more realistic than present CA models and is able to reproduce various flow-density relationships including revered λ - shaped with upward concave and bell-shaped fundamental diagrams that existing CA models are hard to reproduce.