Threephase theory of city traffic: Moving synchronized flow patterns in undersaturated city traffic at signals
Abstract
Threephase traffic flow theory of city traffic has been developed. Based on simulations of a stochastic microscopic traffic flow model, features of moving synchronized flow patterns (MSP) have been studied, which are responsible for a random timedelayed breakdown of a greenwave (GW) organized in a city. A possibility of GW control leading to the prevention of GW breakdown has been demonstrated. A diagram of traffic breakdown in undersaturated traffic (transition from under to oversaturated city traffic) at the signal has been found; the diagram presents regions of the average arrival flow rate, within which traffic breakdown can occur, in dependence of parameters of the timefunction of the arrival flow rate or/and signal parameters. Physical reasons for a crucial difference between results of classical theory of city traffic and threephase theory are explained. In particular, we have found that undersaturated traffic at the signal can exist during a long time interval, when the average arrival flow rate is larger than the capacity of the classical theory; the classical capacity is equal to a minimum capacity in threephase theory. Within a range of the average arrival flow rate between the minimum and maximum signal capacities, undersaturated traffic is in a metastable state with respect to traffic breakdown. We have distinguished the following possible causes for the metastability of undersaturated traffic: (i) The arrival flow rate during the green phase is larger than the saturation flow rate. (ii) The length of the upstream front of a queue at the signal is a finite value. (iii) The outflow rate from a MSP (the rate of MSP discharge) is larger than the saturation flow rate.
 Publication:

Physica A Statistical Mechanics and its Applications
 Pub Date:
 March 2014
 DOI:
 10.1016/j.physa.2013.11.009
 Bibcode:
 2014PhyA..397...76K