A theory of traffic flow in automated highway systems

This paper presents a theory for automated traffic Bow, based on an abstraction of vehicle activities like entry, exit and cruising, derived from a vehicle's automatic control laws. An activity is represented in the Row model by the space and time occupied by a vehicle engaged in that activity. The theory formulates Traffic Management Center (TMC) plans as the specification of the activities and velocity of vehicles, and the entry and exit flows for each highway section. We show that Rows that achieve capacity can be realized by stationary plans that also minimize travel time. These optimum plans can be calculated by solving a linear programming problem. The theory permits the study of transient phenomena such as congestion, and TMC feedback traffic rules designed to deal with transients. We propose a ''greedy'' TMC rule that always achieves capacity but does not minimize travel time. We undertake a microscopic study of the ''entry'' activity, and show how lack of coordination between entering vehicles and vehicles on the main line disrupts traffic Bow and increases travel time. We conclude by giving;some practical indication of how to obtain the space and time usage of activities from vehicle control laws. Finally, we illustrate the concepts presented in this paper with two examples of how the model is used to calculate the capacities of a one-lane automated highway system. In one example we study market penetration of adaptive cruise control and in the second example we study the effect of platooning maneuvers in a platooning architecture for AHS. Copyright (C) 1996 Elsevier Science Ltd