Multi-Gated Perimeter Flow Control of Transport Networks

This paper develops a control scheme for the multi-gated perimeter traffic flow control problem of urban road networks. The proposed scheme determines optimally distributed input flows (or feasible entrance link green times) for a number of gates located at the periphery of a protected network area. A macroscopic model is employed to describe the traffic dynamics of the protected network. To describe traffic dynamics outside of the protected area, we augment the basic state-space model with additional state variables to account for the queues at store-and-forward origin links at the periphery. We aim to equalise the relative queues at origin links and maintain the vehicle accumulation in the protected network around a desired point, while the system's throughput is maximised. The perimeter traffic flow control problem is formulated as a convex optimal control problem with constrained control and state variables. For real-time control, the optimal control problem is embedded in a rolling-horizon scheme using the current state of the whole system as the initial state as well as predicted demand flows at entrance links. A meticulous simulation study is carried out for a 2.5 square mile protected network area of San Francisco, CA, including fifteen gates of different geometric characteristics. Results demonstrate the efficiency and equity properties of the proposed approach to better manage excessive queues outside of the protected network area and optimally distribute the input flows

On the stability of traffic perimeter control in two-region urban cities

In this paper, stability analysis of traffic control for two-region urban cities is treated. It is known in control theory that optimality does not imply stability. If the optimal control is applied in a heavily congested system with high demand, traffic conditions might not change or the network might still lead to gridlock. A city partitioned in two regions with a Macroscopic Fundamental Diagram (MFD) for each of the regions is considered. Under the assumption of triangular MFDs, the two-region MFDs system is modeled as a piecewise second-order system. Necessary and sufficient conditions are derived for stable equilibrium accumulations in the undersaturated regimes for both MFDs. Moreover, the traffic perimeter control problem for the two-region MFDs system is formulated. Phase portraits and stability analysis are conducted, and a new algorithm is proposed to derive the boundaries of the stable and unstable regions. Based on these regions, a state-feedback control strategy is derived. Trapezoidal shape of MFDs are also addressed with numerical solutions. (C) 2012 Elsevier Ltd. All rights reserved

Estimating MFDs in simple networks with route choice

The concept of the Macroscopic Fundamental Diagram (MFD) is elegant and attractive because it provides a global view of traffic behavior and performance at a network level. However, recent research shows that the MFD shape can be influenced by local traffic heterogeneities. Notably, route choices and heterogeneous local capacities may drive uneven (in space) or inconsistent (in time) distributions of congestion and then affect the shape and the scatter of the MFD. We are far from having a global understanding of the connections between local phenomena and the resulting MFD. This paper first aims to improve existing MFD estimation method for a succession of links with traffic signals. The new method overcomes previous limitations, notably regarding to the topology and signal settings regularities, by fully utilizing the receipts of the variational theory. Then, a single network with several parallel routes is investigated. MFDs on different routes are estimated with the variational method and then aggregated in a unified MFD for stationary and dynamic conditions and different sorts of equilibria (user and system optimum). It appears that the flow distribution among routes smoothly varies with respect to the total flow either in free-flow or congestion situations. Such a distribution is much more rough for system optimum, where it presents some discontinuities and is far from equity. This means that a control strategy able to lead such a network to the perfect system optimum would be hard to tune, especially in the congested regime. However, being able to determine the MFD corresponding to the system optimum provides a valuable reference to estimate the current efficiency of the considered network. Case studies for different simple networks and insights for generalization at the city level are proposed. (C) 2013 Elsevier Ltd. All rights reserved

Multimodal, intermodal and terminals

The chapter looks at rail freight terminals, rail--sea interfaces, in particular, as part of a multimodal, or integrated transportation network. Terminals are key infrastructure for linking individual transport modes and governing and managing their interchange in a manner that creates a seamless and sustainable transportation system. Therefore, their performance is critical for maximising transport efficiency and modes integration. This chapter focused on how to measure the operational performance of rail freight terminals in a framework of integrated transportation network. In an increasingly competitive and commercialised world, there is an increasing demand to be able to rank transport options and routes in some way. Drawing on new material, this talk attempts to outline possible methods for how to measure the performance of rail terminals. It focuses on the identification of suitable methods to assess performance by key indicators. Intermodality demands for going beyond safeguarding the individual modes to ensuring the security of the intermodal inter-faces (terminals), the nodes that link and integrate passenger and freight flows. That demands for an integrated holistic approach built on the collaboration between international, national organisations and operators. The study put emphasis on the security challenges and threats to freight transport generally and in rail-sea interfaces more specifically. It moves onto the regulations already governing security in rail-sea interfaces. Finally, it focus on the role that infrastructure planning can play in improving security and offer some conclusions and recommendations for the futur

The N-Dimensional City: Establishing a Vitality Driven Framework for Volumetric Building Networks Through Parametric Design

The architectural concept of a city within a city, or a three-dimensional urban realm, aims to engage the public and bring the vitality of the city into the building. This concept often manifests in the form of grade-separated pedestrian networks, promenades through buildings, roof terraces, sky-bridge connections between towers, and towers that morph together—creating the urban realm throughout volumetric space. The N-Dimensional City investigates a recurring theme of this “volumetric architecture” typology throughout architectural history from a critical perspective. While the type originated from the Soviet era social condenser as a means of creating social equity, volumetric architecture grew to the height of its popularity in capitalist North America with the construction of private building networks throughout the Modern era. Often initiated by the private sector and constructed piecemeal, without integration into the city’s master plan or regulations, many of these volumetric cities experienced a desolated ground plane and the amplification of existing social and economic problems. Rather than producing the social equity envisioned by the building type’s progenitors, the resultant profit-driven spatial organization reinforced segregation, inequality, and commercialism in these urban centres. With a contemporary resurgence of interest in volumetric architecture, signaled by the World Trade Center redevelopment competition in which almost all finalists produced a variation of the type, the thesis aims to resolve the apparent shortcomings volumetric architecture has in achieving its goal of vitality and equity throughout the entirety of a three-dimensional public realm. The thesis adopts the values instilled into Jane Jacobs’ work as its goal for volumetric architecture, including universal access to the city and its movement, inclusive communities, equitable economic opportunities, and a holistic increase to the city’s land value. The City of Toronto is taken as an ideal site to test the building type, as a city with both a history of quasi-public volumetric architecture including the PATH and the Eaton Centre, as well as a recent resurgence of the type in private developments such as City Place and Pier 21. Undergoing a rapid period of construction, the unrestricted powers of the Ontario Municipal Board have undermined the municipality’s ability to direct development in accordance with the Ontario Growth Plan—instead ruling a majority of cases in favour of the development industry against the advisement of the city’s planners. This regulatory vacuum produces a volatile environment for volumetric architecture, in which existing precedents have demonstrated the ability for a profit-driven building network to buttress the city’s existing socio-economic problems through what effectively became a spatial oligopoly and the privatization of the commons. In response to volumetric architecture’s ambition to create an extension of the public realm throughout three-dimensional space, the work of Jane Jacobs is used to form an understanding of how physical qualities of the built environment, designated as urban resources, produce vitality by catalyzing informal uses of public space. Adapting her work from the planar public realm of the old city, Jacobs’ sociological study is codified into a system of discrete actors and processes that can be replicated throughout the three-dimensional field, thus formulating a vitality-driven framework for the volumetric city. The thesis work takes a parametric approach, creating a custom tool written in Processing that simulates the development of the city over time and under a variety of regulatory and stylistic conditions by abstracting the city into a field of voxels with assignable properties. Negotiating the territory between architectural design, urban regulations, and economic forces of the development industry, the parametric tool projects an image of how a vitality-driven model of the volumetric city compares to its profit-driven counterpart, and to the traditional planar city. The N-Dimensional City reveals a not too distant future, prompting a reflection on the qualities of the city that we collectively value as a society, and how these can be developed by the architecture we build today

Dynamics of Long-Life Assets: From Technology Adaptation to Upgrading the Business Model

The editors present essential methods and tools to support a holistic approach to the challenge of system upgrades and innovation in the context of high-value products and services. The approach presented here is based on three main pillars: an adaptation mechanism based on a broad understanding of system dependencies; efficient use of system knowledge through involvement of actors throughout the process; and technological solutions to enable efficient actor communication and information handling.The book provides readers with a better understanding of the factors that influence decisions, and put forward solutions to facilitate the rapid adaptation to changes in the business environment and customer needs through intelligent upgrade interventions. Further, it examines a number of sample cases from various contexts including car manufacturing, utilities, shipping and the furniture industry. The book offers a valuable resource for both academics and practitioners interested in the upgrading of capital-intensive products and services