Capacity drop: a comparison between stop-and-go wave and standing queue at lane-drop bottleneck

Abstract

In freeways, the capacity drop means that the maximum traffic flow is higher than congestion discharge rates there. Various capacity drop magnitudes have been empirically observed before. But the mechanism behind this wide capacity drop range is not yet found. This contribution fills in the gap by relating the congestion discharge rates to different congestions in empirical observations. Two days' data show that the outflows of stopand-go waves are always lower than those of standing queues. Different discharge rates, ranging from 5220 to 6040 veh/h at the same site, always accompany different congestion states. Moreover, the different observations show that a higher discharge rate means a higher density in the free-flow branch in the fundamental diagram. This contribution shows that discharging rates probably could be controlled by transforming the congestion states. For instance, transforming a stop-and-go wave into a standing queue at a bottleneck might increase the bottleneck throughput.

A Microscopic Investigation Into the Capacity Drop: Impacts of Longitudinal Behavior on the Queue Discharge Rate

“…The magnitude of the capacity drop is not constant. Empirical data show that the queue discharge rate varies considerably at the same location (Chung et al 2007, Yuan et al 2016. This is shown to correlate well with congestion states (Yuan et al 2015, Oh andYeo 2015).…”

“…However, a reduction of capacity does not only occur at bottlenecks. In fact, some research (Kerner 1998, Yuan et al 2016, Oh and Yeo 2015 report on queue discharge rates out of stop-and-go waves on homogeneous freeway sections, which are also lower than the capacity. In this paper, we also call that a capacity drop.…”

A kinematic wave model in Lagrangian coordinates incorporating capacity drop: Application to homogeneous road stretches and discontinuities

“…The shock wave shown as dashed line has been expected in Figure 6(c). Note that, this shock wave has been frequently observed on freeways, see [4] and [35].…”

“…The studied cases around nodes in this paper have been empirically observed in [4] and [35]. Because empirical observations in [4] and [35] show different congested states at lane-drop and on-ramp bottleneck, this work uses different number (state 8 and state 9) to denote the congested state of the standing queue forming at lane-drop and on-ramp bottleneck, respectively.…”

“…Because empirical observations in [4] and [35] show different congested states at lane-drop and on-ramp bottleneck, this work uses different number (state 8 and state 9) to denote the congested state of the standing queue forming at lane-drop and on-ramp bottleneck, respectively. In Case 4, the on ramp is one-lane and the merging ratio γ = 0.35.…”