Collective behavior and the identification of phases in bicycle pelotons

• A method for identifying phases in bicycle pelotons is proposed.
• Collective behavior in bicycle pelotons is characterized by two distinct phases.
• Lateral synchronization occurs only in the high density phase.
• High velocities give rise to the low density “stretched” phase.
• Collective behavior reflects both energy savings and tactics in competition.

As an aggregate of cyclists, a peloton exhibits collective behavior similar to flocking birds or schooling fish. Positional analysis of cyclists in mass-start velodrome races allows quantitative descriptions of peloton phases based on observational data. Data from two track races are analyzed. Peloton density correlates well with cyclists’ collective power output in two clear phases, one of low density, and one of high density. The low density “stretched” phase generally indicates low frequency positional-change and single-file synchronization. The high density “compact” phase may be further divided into two phases, one of which is a laterally synchronized phase, and another is a high frequency and magnitude positional-change phase. Phases may be sub-divided further into acceleration and deceleration regimes, but these are not quantified here. A basic model of peloton division and its implications for general flocking behavior are discussed.