Further Studies on Single-Lane Bus Flow: Transient Characteristics

The results of a series of experiments carried out to determine the transient characteristics of a platoon of buses starting and stopping along an exclusive right of way are reported. By using a six-bus platoon on a 2½-mile test facility, the effects of such factors as platform spacing, station spacing, speed, delay, etc., on platoon dynamics were investigated. The space-time trajectories of the lead and last vehicles have been examined in detail and a number of interesting features describing the bus platoon dynamics are presented. In particular, the results indicate that the dynamics of this cyclic operation of starting at one position and stopping at another is highly predictable. The motion of the platoon through such a cycle can be described in terms of a starting transient, a steady state, and a stopping transient, each of which is made up of simple and qualitatively describable features. Furthermore, the “smoothness” of the acceleration of a platoon to a steady state is found to be strongly dependent on starting delay, vehicle performance, and intervehicle spacing at the starting position. In addition, the experimental observations have been compared with the theoretical results obtained from numerical solutions of the linear car-following model of single-lane traffic flow.