Representation requirements for perfect first-in-first-out verification in continuous flow dynamic models
Representation requirements for perfect first-in-first-out verification in continuous flow dynamic models
复制标题
DOI：
10.1016/j.trb.2017.02.002
复制
发表时间：
2017-06
影响因子：
6.8
通讯作者：
H. Bar-Gera;M. Carey
中科院分区：
文献类型：
--
作者：
H. Bar-Gera;M. Carey
交通动态模型需要解决许多问题。其中之一是管理不同流量流（商品）的优先级的方式。当流被视为连续流时，这尤其具有挑战性。通常将先进先出（FIFO）规则视为设置优先级的基线，但大多数实际连续流动态模型并不完全满足FIFO。本文研究了与完全遵守网络范围的FIFO相关的困难。我们研究了六种不同的方法来表示网络上的动态流解决方案，并针对每种表示方法，我们讨论了它是否足以验证FIFO，验证过程是否是有限的，以及是否可以直接暗示证明FIFO。在整个评估过程中，考虑了FIFO的八种替代定义，其中七种基本上是等效的，而最后一种定义则不是，因此可以被视为“弱”FIFO。最有希望的表示似乎是表示为“队列束”的表示，虽然比其他表示更抽象，但支持这种表示直接显示了完美的FIFO满意度。这种表示的进一步评估仍然是一个主题，为未来的研究。简而言之，本分析的主要结论是，为了满足完美的网络范围的FIFO的流的离散化元素的数量可能应该被允许快速增长和无限的模型持续时间，它不能被确定的先验。这些关于在连续流动态模型中结合FIFO的挑战的见解，也可能与其他基于行为的优先级规则相关，可以帮助建模者和从业者设定关于有限维连续流动态模型中可以实现的优先级规则的控制水平的现实期望。
Dynamic models of traffic require answers for many issues. One of them is the way priorities of different traffic streams (commodities) are managed. This is particularly challenging when flows are treated as continuous. It is common to consider the First-In-First-Out (FIFO) rule as a baseline for setting priorities; but most practical continuous flow dynamic models do not satisfy FIFO perfectly. This paper examines the difficulties associated with full adherence to network-wide FIFO.We examine six different ways to represent dynamic flow solutions over a network, and for each representation we discuss whether it is sufficient for verifying FIFO, whether the verification process is finite, and whether proving FIFO can be directly implied. Throughout the evaluation eight alternative definitions of FIFO are considered, seven of them are shown to be essentially equivalent, while the last definition is not, and may therefore be considered as “weak” FIFO. The most promising representation appears to be the one denoted as “cohort bundles,” while somewhat more abstract than the other representations, supporting this representation directly shows perfect FIFO satisfaction. Further evaluation of this representation remains a subject for future research.In a nutshell, the key conclusion of this analysis is that in order to satisfy perfect network-wide FIFO the number of discretized elements of flow should probably be allowed to grow quickly and unboundedly with model duration, and it cannot be determined a-priori. These insights about the challenges of incorporating FIFO in continuous flow dynamic models, which may be relevant also for other behavior-based priority rules, can help modelers and practitioners set realistic expectations regarding the level of control over priority rules that can be achieved within finite-dimensional continuous flow dynamic models.