Effect of autonomous driving on traffic breakdown in mixed traffic flow: A comparison of classical ACC with three-traffic-phase-ACC (TPACC)

Abstract

In this paper, an analysis of the effect of autonomous driving vehicles on traffic breakdown in mixed traffic flow consisting of randomly distributed human driving and autonomous driving vehicles is made. Autonomous vehicles based on classical (standard) adaptive cruise control (ACC) in a vehicle and on an ACC in the framework of three-phase traffic theory (TPACC – Three-traffic-Phase ACC) introduced recently [Phys. Rev. E 97 (2018) 042303] are considered. Due to the particular importance of characteristics of traffic breakdown (transition from free traffic flow to congested traffic) for almost all approaches to traffic control and management in traffic networks, the basis of this paper is a study of the effect of autonomous vehicles on the probability of traffic breakdown and on stochastic highway capacity in mixed traffic flow. We show that within a wide range of dynamic parameters of classical ACC, the ACC-vehicles can deteriorate the traffic system considerably while initiating traffic breakdown and reducing highway capacity at a bottleneck. Contrarily, in the same range of parameters of dynamic rules of TPACC, the TPACC-vehicles either do not effect on traffic characteristics or sometimes can even improve them. To understand physical reasons for the effect of classical ACC- and TPACC-vehicles on traffic breakdown, we introduce a model of ACC that can be considered a combination of dynamic features of classical ACC and TPACC. With the use of this model, we find how the amplitude of a local speed disturbance caused by the ACC in a vicinity of a bottleneck and the probability of traffic breakdown depends on the dynamic parameters of the ACC. To emphasize that the deterioration of the characteristics of mixed traffic flow through classical ACC-vehicles is not associated with a well-known effect of string instability of platoons of autonomous vehicles, we limit by a consideration of only such classical ACC-vehicles whose platoon satisfies condition for string stability.