Transportation networks are facing severe congestion due to the increasing burden of traffic demand and unexpected incidents. Therefore enhancing the network capacity flexibility is the urgent task of transportation managers. Apart from the expansion of road links, economic approaches such as congestion pricing are more effective ways of improving network capacity flexibility. However, congestion pricing often receives objection since it brings excessive travel cost to travelers. A more acceptable economic scheme of adjusting route choice behavior might be offering a subsidy, in a manner of reducing existing charges. In light of this incentive, we propose a solution in the form of multimodal subsidy design with the goal of optimizing network capacity flexibility. To validate the general applicability of the proposed multimodal subsidy schemes, we evaluate and quantify the network capacity flexibility by adopting three different measurement approaches, which are based on the concepts of reserve capacity, total capacity flexibility, and limited capacity flexibility respectively. Three mathematical models are established using these different capacity flexibility measurement approaches, each of which is formulated as a bi-level programming problem. The upper-level problem is to optimize the values of various subsidies, including road link subsidies, parking subsidies, and metro ticket subsidies to enhance the network capacity flexibility. The lower-level problem is a nested-logit based variation inequality program that considers multimode traffic and predicts how drivers and passengers react to the subsidy decision delivered from the upper-level problem. Numerical examples are provided to demonstrate how the proposed subsidy schemes affect network capacity flexibility as well as to compare the effects of different subsidy schemes.

由于交通需求负担的增加和突发事件，交通网络正面临严重的拥堵。因此，提高网络容量的灵活性是运输管理者的紧迫任务。除了扩展道路连接外，拥堵定价等经济方法也是提高网络容量灵活性的更有效方法。但是，由于拥挤定价会给旅行者带来过多的旅行费用，因此常常会引起反对。一种更可接受的调整路线选择行为的经济方案可能会以减少现有费用的方式提供补贴。鉴于这种激励，我们以多模式补贴设计的形式提出了一种解决方案，旨在优化网络容量的灵活性。为了验证所提议的多式联运补贴计划的普遍适用性，我们采用三种不同的测量方法来评估和量化网络容量的灵活性，这三种方法分别基于备用容量，总容量灵活性和有限容量灵活性的概念。使用这些不同的容量灵活性度量方法建立了三个数学模型，每种模型都被表述为双层编程问题。上层问题是优化各种补贴的价值，包括道路链接补贴，停车补贴和地铁票补贴，以增强网络容量的灵活性。下层问题是一个基于嵌套logit的变分不等式程序，该程序考虑多模式交通并预测驾驶员和乘客对上层问题提供的补贴决策的反应。