On the use of Lagrangian observations from public transport and probe vehicles to estimate car space-mean speeds in bi-modal urban networks

The Macroscopic Fundamental Diagram (MFD) has been recognized as a powerful framework to develop network-wide control strategies. Recently, the concept has been extended to the three-dimensional MFD, used to investigate traffic dynamics of multi-modal urban cities, where different transport modes compete for, and share the limited road infrastructure. In most cases, the macroscopic traffic variables are estimated using either loop detector data (LDD) or floating car data (FCD). Taking into account that none of these data sources might be available, in this study we propose novel estimation methods for the space-mean speed of cars based on: (i) the automatic vehicle location (AVL) data of public transport where no FCD is available; and (ii) the fused FCD and AVL data sources where both are available, but FCD is not complete. Both methods account for the network configuration layout and the configuration of the public transport system. The first method allows one to derive either uni-modal or bi-modal macroscopic fundamental relationships, even in the extreme cases where no LDD nor FCD exist. The second method does not require a priori knowledge about FCD penetration rates and can significantly improve the estimation accuracy of the macroscopic fundamental relationships. Using empirical data from the city of Zurich, we demonstrate the applicability and validate the accuracy of the proposed methods in real-life traffic scenarios, providing a cross-comparison with the existing estimation methods. Such empirical comparison is, to the best of our knowledge, the first of its kind. The findings show that the proposed AVL-based estimation method can provide a good approximation of the average speed of cars at the network level. On the other hand, by fusing the FCD and AVL data, especially in case of sparse FCD, it is possible to obtain a more representative outcome regarding the performance of multi-modal traffic.     

The politics of collective public participation in transportation decision-making

Citizen involvement in transportation planning is typically modeled on a liberal democracy in which individuals express their preferences about a project. In this paper we present an analysis based on interviews with stakeholders whose involvement was grounded in a complementary model of public participation, one in which an organized community used collective action (instead of only individual expression), and worked both within and outside of the formal public involvement process to influence the design of an arterial highway in their neighborhood. This case reflects a commonplace context for public participation: residents opposing a highway expansion and the negative effects of heavy traffic in neighborhoods. The problem presented in this case is that the process for citizen involvement was not designed to fully utilize the community’s collective capacity. Three aspects of collective action—representation, the ability to shape a policy agenda, and methods of engagement—were contested in the public participation process. We argue that these conflicts around collective action in the public participation process exposed its “one-way communication,” and enabled a different kind of political process in which neighbors’ organizing was powerful and influenced decisions.     

A dynamic station strategy to improve the performance of flex-route transit services

As an innovative combination of conventional fixed-route transit and demand responsive service, flex-route transit is currently the most popular type of flexible transit services. This paper proposes a dynamic station strategy to improve the performance of flex-route transit in operating environments with uncertain travel demand. In this strategy, accepted curb-to-curb stops are labeled as temporary stations, which can be utilized by rejected requests for their pick-up and drop-off. The user cost function is defined as the performance measure of transit systems. Analytical models and simulations are constructed to test the feasibility of implementing the dynamic station strategy in flex-route transit services. The study over a real-life flex-route service indicates that the proposed dynamic station strategy could reduce the user cost by up to 30% without any additional operating cost, when an unexpectedly high travel demand surpasses the designed service capacity of deviation services.     

Valuation of strategic options in public–private partnerships

This paper investigates the feasibility of and develops an economic valuation model for strategic options in Comprehensive Development Agreements (CDAs). A CDA is a form of public–private partnership whereby the right to price and collect revenues from toll roads is leased to a private entity for a long but finite period of time. In exchange, this provides local and state governments with a quick influx of cash and/or additional infrastructure. Uncertainty associated with such long-term leases is of substantial public concern. This paper examines five different strategic options, namely a buyout option, a conditional buyout option, a revenue-sharing option, and two types of minimum revenue guarantee options. The buyout option in particular could give the public sector additional control over the future use of leased facilities and address potential concerns regarding long-run uncertainty and possible unforeseen windfalls for the private sector. The paper’s contributions include the analysis, feasibility assessment and valuation of several strategic options, sensitivity analysis of the solutions, an economic consumer demand-based revenue model for purposes of cash flow simulation, and analysis of option price sensitivity to “moneyness”. The main conclusion is that strategic options can provide useful risk reduction, but generally have significant value relative to the lease itself. By scaling down payoffs, options could be realistically included in CDAs and other PPPs. For some parameter values, option values to the developer and public authority are offsetting, allowing for costless risk reduction.     

Exposing the role of exposure: Public transport network risk analysis

Network risk assessment takes into consideration the probability that adverse events occur and the impacts of such disruptions on network functionality. In the context of transport networks, most studies have focused on vulnerability, the reduction in performance indicators given that a disruption occurs. This study presents and applies a method to explicitly account for exposure in identifying and evaluating link criticality in public transport networks. The proposed method is compared with conventional measures that lack exposure information. A criticality assessment is performed by accounting for the probability of a certain event occurring and the corresponding welfare loss. The methodology was applied for a multi-modal public transport network in the Netherlands where data concerning disruptions was available. The results expose the role of exposure in determining link criticality and overall network vulnerability. The findings demonstrate that disregarding exposure risks prioritizing links with high passenger volumes over links with a higher failure probability that are significantly more critical to network performance. The inclusion of exposure allows performing a risk analysis and has consequences on assessing mitigation measures and investment priorities.     

论完善权力的监督和制约

权力是统治阶级为了维护自身利益而以强制性手段体现出来的国家意志。在我国,权力主要掌握在人民群众利益的代表——中国共产党手中,就其性质而言,它产生于人民并服务于人民。权力本身是一把“双刃剑”,运用得好,可以利党利国利民,造福社会;一旦失控,往往就会产生腐败,遗患社会。要进行社会主义现代化建设,必须要对权力进行监督和制约。     

基于智能公交系统的公交优先发展战略研究

分析我国当前实施公交优先政策的方法和智能公共交通系统的发展情况,结合国外城市解决公交发展问题的经验,提出发展智能公共交通系统是实现我国城市公交优先政策的最佳途径。另外,讨论了我国智能公共交通系统发展的不足之处,结合实现公交优先政策中遇到的问题,对我国智能公交系统的发展与公交优先发展战略的研究提出建议。     

社区主义:公共伦理建设的新走向

当代中国正处在以城市化为主导的社会转型的关键时期 ,社会出现了种种不协调 ,需要相应价值尺度来引导。而以国家理性为价值尺度的“国家主义”在中国正趋向衰微 ,以个人理性为终极价值尺度的“个人主义”在中国无法植根 ,造成了社会公共伦理的“空场”,从而说明以公共理性为核心 ,以“个人自由加公共利益”为精神实质的“社区主义”作为一种新的社会精神价值取向应时而生 ,适应了中国当代城市化进程的需要     

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城市公共交通发展模式选择问题是我国城市在实施会共交通优先发展战略过程中一个迫切需要解决的问题.文章在分析了当前存在的几种城市主要公共交通模式(常规公交、快速公交系统、轻执和地铁)的技术经济特性的基拙上，结合城市公交发展模式选择问题的特点，建立了城市公共交通发展模式决策矩阵，通过对多属性决策问题的求解来进行城市公共交通发展模式的选择，并定义了城市公共交通模式供求匹配指数来验证所选模式的客流适应性.最后，以西安市为例验证了文章提出的方法的适用性和合理性，提出了西安市城市公共交通建议发展模式.     

违宪审查的启动机制

在当代中国，《宪法》、《立法法》关于违宪审查的规定虽然不够完善，但毕竟初步建立起了违宪审查制度。但是，在法治实践中却很少真正启动违宪审查程序。怎样启动违宪审查，是一个理论上需要迫切解决的问题。本正是从这一角度出发，探讨必须赋予公民违宪申诉权以启动违宪审查，达到维护法制统一，保障人民权利的目的。