Defining Highway Node Acceptance Capacity (HNAC): Theoretical Analysis and Data Simulation

Abstract

A new concept of Highway Node Acceptance Capacity (HNAC) is proposed in this paper inspired by a field data observation. To understand HNAC in microscopic view, boundary condition of successful merging is found using car-following behaviours and lane-changing rules, which could also explain traffic oscillations. In macroscopic view, linear positive relationship between HNAC and background traffic volume is obtained based on moving bottleneck. To determine the explicit form of the relationship, data simulation considering car-following behaviours and traffic flow theory is used. In the results, the synchronization phenomenon of oscillation in on-ramp (with respect to main road) and intersected road is found. The explicit equation of HNAC is determined based on standard deviation and correlation coefficient analysis, and also proved to be accurate with model validation, which is helpful in studies related to propagation mechanism of traffic emergencies on highway network.

Forecasting Spatiotemporal Boundary of Emergency-Event-Based Traffic Congestion in Expressway Network Considering Highway Node Acceptance Capacity

“…That is because the current literature cannot accurately evaluate whether the congestion (spatiotemporal boundary) will spread into the intersected expressway sections through interchanges. This problem is well addressed by HNAC defined in our previous work [23]. Following that, this study proposes a method which integrates kinetic wave theory, volumedensity model and CTM to predict the spatiotemporal boundary of emergency-event-based traffic congestion propagation in expressway networks.…”

“…First, this method was usually adopted to analyze a traffic congestion spatiotemporal boundary in a road segment, studies on large-scale networks were limited. This is because the judgement of whether the spatiotemporal boundary will spread into an intersected road through an interchange could not be easily and accurately answered [23]. Although some research focus on network were found [16], most of these models were developed and calibrated using simulations or unrealistic assumptions; large-scale field data depicting real-time traffic flows are needed.…”

“…As introduced in Section 1, HNAC represents the maximum merging traffic volume from intersected expressway to targeted expressway in an interchange, through the merging ramp [23]. To be more specific, combining the contents in Figures 1 and 2, when traffic flow in emergency-event BRSs is moving slowly (notice, not blocked), it still has the ability to receive some merging volume.…”

“…In an interchange area, the traffic volume that can merge into the targeted expressway from the intersected expressway connected by a ramp is typically limited. We define the maximum merging traffic volume as the highway node acceptance capacity (HNAC) [23]. In a real driving environment, if the traffic volume merging into an expressway exceeds the HNAC of the targeted road section (i.e., the expressway where the flow will merge into), dramatic traffic oscillations and serious traffic congestion will be formed in the merging ramp.…”