A Theory of Traac Ow in Automated Highway Systems

This paper presents a theory for automated tra c ow 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 ow model by the space occupied by a vehicle engaged in that activity The theory formulates TMC tra c plans as the speci cation of the activities and speed of vehicles and the entry and exit ows for each highway section We show that ows 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 We illustrate these concepts by calculating the capacities of a one lane automated highway system and compare adaptive cruise control and platooning strategies for automation The theory permits the study of transient phenomena such as congestion and TMC feedback tra c rules designed to deal with transients We propose a greedy TMC rule that always achieves capacity but does not minimize travel time Finally 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 tra c ow and increases travel time