Numerical Investigation of Stop-and-Go Traffic Patterns Upstream of Freeway Lane Drop

Freeway lane drops are typical sites where long queues and stop–start traffic waves can be observed. A theory was recently developed to explain the formation of traffic oscillations upstream of a freeway lane drop-in. Using that theory, this paper carries out a numerical investigation to explore how parameters characterizing the driving behavior at and the geometry of a lane-drop site may affect these oscillatory patterns. The effects of five factors–-distance between the merging sign and the taper, travel demand, remaining capacity, overall aggressiveness of drivers, and geometry of the lane drop–-are studied. It is found that a lane-drop site with low remaining capacity, high travel demand, short distance between the merging sign and the taper, closely matching numbers of drivers desiring to take the through lanes and to take the shoulder lanes, and an imbalance in merging priorities at the taper location is most likely to produce oscillations with short periods and high oscillation amplitudes in flow. Furthermore, the speeds at which the oscillations propagate and the periods of oscillations are in the same order of magnitude as those observed and can be made to match the observed values closely with the proper choice of parameters. Potential management measures to alleviate or eliminate such oscillations are also discussed.