Individual Accessibility Revisited: Implications for Geographical Analysis in the Twenty‐first Century

Analytical methods for evaluating accessibility have been based on a spatial logic through which the impedance of distance shapes mobility and urban form through processes of locational and travel decision making. These methods are not suitable for understanding individual experiences because of recent changes in the processes underlying contemporary urbanism and the increasing importance of information and communications technologies (ICTs) in people's daily lives. In this paper we argue that analysis of individual accessibility can no longer ignore the complexities and opportunities brought forth by these changes. Further, we argue that the effect of distance on the spatial structure of contemporary cities and human spatial behavior has become much more complicated than what has been conceived in conventional urban models and concepts of accessibility. We suggest that the methods and measures formulated around the mid‐twentieth century are becoming increasingly inadequate for grappling with the complex relationships among urban form, mobility, and individual accessibility. We consider some new possibilities for modeling individual accessibility and their implications for geographical analysis in the twenty‐first century.     

Hub-and-Spoke Networks in Air Transportation: An Analytical Review

In this review we survey advances in analysis of the hub location problem and its variants. In the course of the review opportunities for enhanced analysis become apparent. We emphasize the most pressing areas for further work. We found that first, research needs to be devoted to developing more reliable heuristics for the multiple assignment model and its extensions and second, that additional research is needed to understand the conditions under which the model will tend to have integer solutions. Research in this area will contribute to the solution of a longstanding puzzle in economics about the allocation of indivisible resources.     

The EU habitats directive: Making the article 6 assessments,the case of Ballyseedy Wood

The Habitats Directive requires that projects likely to have a detrimental impact upon a protected habitat must be subject to an assessment of that impact. If that assessment is negative the project may only proceed if there is an absence of alternative solutions and, if there are no alternatives, where there are imperative reasons of overriding public interest. This article looks at the interpretation of those assessments and their practical implications for a road improvement project in County Kerry in the west of Ireland. The Ballyseedy Wood case demonstrates the level of protection from development now afforded to designated wildlife sites by the European Union.     

Towards a Political Economy of Social Infrastructure: Contesting “Anti-Social Infrastructures” in London

In this paper, we develop a situated and intersectional urban political economy approach to social infrastructure. This approach contrasts with a growing body of liberal urban geography, which offers an optimistic account of how shared spaces afford encounter and social connection. We present four arguments about why such outcomes cannot be assumed, which are informed by a case of contested redevelopment in the London borough of Haringey. First, social infrastructures express power relations, enacting distinct visions of “the social”, that are at times premised on the denigration of other forms of collective life as anti-social. Second, elite social infrastructures are increasingly central to speculative urban development, serving to procure consent for, and valorise, investment. Third, other social infrastructures are essential networks of social reproduction and survival, especially for diverse working-class communities: demolition and displacement mean infrastructural disruption. Finally, unequal political economies of social infrastructure are a realm of structural antagonism over urban citizenship (un)making.     

The Tide of History

Two stories are told simultaneously: one that may have been, and one that yet might be. The story of the voyage that might have been is based on archaeological evidence provided by the earliest shipwreck discovered in the New World. These two stories are set in different eras to demonstrate certain constants in the human drive to explore the unknown, in the methods used, and in the consequences encountered.     

Extensions to the Hub Location Problem: Formulations and Numerical Examples

Although a tremendous amount of analytical research is being conducted on the hub location problem, few models exist that extend the number of characteristics found in actual hub-and-spoke networks. Four extensions are presented in this paper: (1) a capacitated network model; (2) a minimum threshold model; (3) a model that endogenously determines the number of open hubs for the network; and (4) a model that incorporates a flow-dependent cost function for the spokes as well as the interhub links. Both the capacitated and the minimum threshold models drop the assumption of a completely interconnected network commonly found in hub location models. Numerical results show that total network costs are often minimized by closing a few interhub links. The third extension is the first known hub location model to determine the optimal number of hubs based on the needs of the network. In this model, the number of open hubs depends on the distribution of flows in the network and how cost effectively the flows can be moved across the network. Previous models that endogenously determined the number of open hubs utilized a fixed cost for establishing each hub in order to limit the number of hubs in the network. The final extension recognizes the potential of all links to amalgamate flows and includes a separate flow-dependent cost function for the spokes in addition to the one for the interhub links. Numerical results are shown for all four models.