Opposing Hysteresis Patterns in Flow and Outflow Macroscopic Fundamental Diagrams and Their Implications
Opposing Hysteresis Patterns in Flow and Outflow Macroscopic Fundamental Diagrams and Their Implications
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DOI：
10.1177/03611981231155421
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发表时间：
2023-03
影响因子：
1.7
通讯作者：
Guanhao Xu;Pengxiang Zhang;V. Gayah;Xianbiao Hu
中科院分区：
文献类型：
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作者：
Guanhao Xu;Pengxiang Zhang;V. Gayah;Xianbiao Hu
两个关键的聚合交通模型是平均网络流量和密度之间的关系（称为网络或流量宏观基本图[flow-MFD]）和行程完成与密度之间的关系（称为网络出口函数或流出MFD [o-FMD]）。在稳态条件下，流量和o-MFD已被证明是相关的平均网络长度和平均行程距离。然而，最近的研究表明，这两种关系可能有不同的模式时，交通条件允许变化：流量MFD表现出顺时针滞后环，而o-MFD表现出逆时针循环。最近的一项研究将这种行为归因于网络中存在瓶颈。本论文证明，即使不存在瓶颈，这种现象也可能出现，并为这些发现提供了另一种但更普遍的解释：车辆的整个行程有助于网络的平均流量，而只有其终点有助于行程完成率。这种滞后也可能被不同长度的行程放大，并且它可能导致o-MFD中的其他模式，例如8字形模式。一个简单的动脉例子被用来证明这一解释，并揭示预期的模式，他们也确定在真实的网络使用的经验数据。然后，一个可压缩的环网络的模拟被用来揭示功能，可能会增加或减少之间的差异流和o-MFD。最后，更现实的模拟，以确认这些行为出现在真实的网络。
Two key aggregated traffic models are the relationship between average network flow and density (known as the network or flow macroscopic fundamental diagram [flow-MFD]) and the relationship between trip completion and density (known as network exit function or the outflow-MFD [o-FMD]). The flow- and o-MFDs have been shown to be related by average network length and average trip distance under steady-state conditions. However, recent studies have demonstrated that these two relationships might have different patterns when traffic conditions are allowed to vary: the flow-MFD exhibits a clockwise hysteresis loop, while the o-MFD exhibits a counter-clockwise loop. One recent study attributes this behavior to the presence of bottlenecks within the network. The present paper demonstrates that this phenomenon may arise even without bottlenecks present and offers an alternative, but more general, explanation for these findings: a vehicle’s entire trip contributes to a network’s average flow, while only its end contributes to the trip completion rate. This lag can also be exaggerated by trips with different lengths, and it can lead to other patterns in the o-MFD such as figure-eight patterns. A simple arterial example is used to demonstrate this explanation and reveal the expected patterns, and they are also identified in real networks using empirical data. Then, simulations of a congestible ring network are used to unveil features that might increase or diminish the differences between the flow- and o-MFDs. Finally, more realistic simulations are used to confirm that these behaviors arise in real networks.