Phantom Traffic: Platoon Formed at Low Traffic Density

Abstract

On a highway, it is generally observed that as traffic flow increases, vehicles tend to travel closely and form platoons. However, sometimes platoons are formed at even a low traffic density and therefore a high traffic speed, and phantom traffic has been believed to be one of the causes. It is necessary to understand the process and characteristics of platoon formation and dispersion for efficient traffic operation and safety, and to understand why phantom traffic is formed even when traffic density is low. This study assumes that the random variation of speed (involuntary speed change) can be a critical factor that is involved in platoon formation and dispersion. A single-lane platoon-generation model based on a simple vehicle movement rule incorporating the random speed variation is developed and the characteristics of vehicle platoons are investigated through a simulation. The results show that random speed variation can be one of the factors related to platoon generation and dispersion. Initial speed and initial spacing also are found to affect the variation of the number and size of platoons.