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  • Series: NECTAR Series on Transportation and Communications Networks Research x
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Edited by Ana Condeço-Melhorado, Aura Reggiani and Javier Gutiérrez

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Ana Condeço-Melhorado, Aura Reggiani and Javier Gutiérrez

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John Östh, Aura Reggiani and Giacomo Galiazzo

In much accessibility research, arbitrary estimates of the distance sensitivity parameters have been used to represent the distance decay parameters in potential accessibility models. These estimates might be considered arbitrary since the choice of value and the choice of the distance decay function is often motivated by statistical indicators of the goodness of fit on spatial flows, given the fact that measures of ‘real’ accessibilities are missing. Starting from these considerations, in this chapter we introduce a new approach, the half-life model originating from the natural sciences, to estimate distance decay parameters. This method is compared with two conventional approaches originating from spatial economic science for the computation of distance decay parameters: the unconstrained and the doubly constrained spatial interaction models. The emerging distance decay parameters will be then considered in the construction of accessibility indicators based on the potential accessibility introduced by Hansen in 1959. In this context, both the mean and the median distance will be taken into account in order to identify MAUP-related issues. The exploration of these three approaches focuses on empirical analyses of accessibility in Sweden at the municipal level for 1993 and 2008. All the emerging accessibility indicators are compared in order to analyse similarities and differences in the hierarchical accessibility levels of the Swedish municipalities. The chapter concludes with some methodological and empirical remarks on the adoption of these three approaches, in the light of possible forecasts and related policy analyses.

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David Philip McArthur, Inge Thorsen and Jan Ubøe

A worker might respond to an unfortunate local labour market situation by commuting or migrating to a zone with better prospects. This decision depends on the labour market accessibility of the worker’s current residential location. A spatial equilibrium model is applied to analyse the interactions between commuting, migration, firm relocation and accessibility. The analysis is based on numerical examples, experimenting with characteristics of the transportation network and the spatial distribution of jobs. We study how the effects of such shocks depend on behavioural responses to different aspects of labour market accessibility. We also study the cumulative causation aspect of accessibility, whereby highly accessible areas attract jobs and workers, further enhancing the accessibility of such zones.

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Thomas W. Nicolai and Kai Nagel

Accessibility is a concept which either looks at how easy it is to reach a certain location from many other locations, or how easy it is to reach other locations or opportunities from a given starting point. This chapter looks at the latter, discussing that this is a quantity that can be defined separately for every point (x,y) in space, rather than treating accessibility as uniform within, say, zones. As a result, accessibility can also be seen as a continuous field A(x,y) in the two-dimensional environment. The chapter then continues to discuss how A(x,y) can be efficiently computed for regional scenarios. The approach combines interpolation of values computed on a grid with fast shortest-path tree computations and information caching for repeated sub-computations of the same quantities, using the econometric logsum term as an example of a possible indicator of accessibility. A Zurich scenario needs about two minutes of computing time on a regular desktop computer in order to compute A(x,y) at a resolution of 100 m x 100 m. As a sensitivity study, workplace accessibility maps are given for free speed car, congested car, bicycle and walking. One can for example observe that accessibility by bicycle is similar to congested car accessibility within the urban area, while it is worse outside and considerably worse when compared to free speed car transport. Similarly, walking accessibility is similar to bicycle and congested car transport in the innermost urban core, but considerably worse everywhere else.

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Laurie A Schintler, Rajendra Kulkarni, Kingsley Haynes and Roger Stough

Recently there have been significant efforts to mine location-sharing services data and other similar types of geo-social digital data to understand and analyse the complexity of human mobility patterns. Of these studies, very few studies have examined how mobility patterns vary across different regions of the United States. This chapter intends to fill this gap in the literature. Specifically, we use bipartite network modelling to derive a set of metrics for characterizing regional variations in the mobility patterns of individuals. Through this study, we also attempt to gain insight on the types of trips that location-sharing services data may represent. Lastly, we use a community detection to derive information on what we refer to as ‘mobility sheds’. For the purpose of this study, we use a sample of Brightkite location-sharing services data, collected by the Stanford Large Network Dataset collection, SNAP.

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Andrea De Montis, Simone Caschili and Daniele Trogu

The aim of spatial autocorrelation is to inspect the organization and structure of spatial phenomena. This statistical method allows one to scrutinize spatial patterns and relationships that generate relevant phenomena in territories under consideration. In fact, spatial phenomena are often self-determining and may positively or negatively influence adjacent units. Autocorrelation analysis pinpoints the mutual influence among spatial units as well as any polarizing effect around a specific area. In this chapter we use spatial autocorrelation analysis to scrutinize the level of spatial dependency of accessibility for commuters in continental US counties on the theoretical basis described above. Counties’ accessibility is computed according to gravity theory (spatial interaction models with impedance function obeying to exponential and power decay impendence functions). The scope of our study is to understand whether space influences counties’ accessibility. We first apply global and local univariate spatial autocorrelation analysis in order to test the hypothesis that counties with higher accessibility positively influence adjacent counties. Finally we test whether accessibility is spatially correlated with socio-demographic variables, such as residential population and income per capita. We develop a bivariate autocorrelation analysis to assess spatial dependencies between the accessibility of US counties and socio-economic variables both at the global and at the local level.

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Maria Henar Sales-Olmedo, Ana Condeço-Melhorado and Javier Gutiérrez

The globalization of population and trade flows yielded an increase of interactions within the international framework. Accessibility indicators are especially suited to represent spatial interaction since they capture two basic factors that determine the amount of flows between a set of places: the opportunities available and the infrastructure used to move those flows. While globalization trends contributed to the weakening of borders, several studies confirm that borders still matter in international trade, and play a significant role in the form of home bias, that is, a marked preference for domestic products. Still, most studies of international accessibility ignore this fact, thus failing to show realistic results. This chapter makes use of gravity equations to calibrate the distance decay parameter as well as a new coefficient to control for the border effect in the market potential indicator. We used official trade data at the country level in the European Union (EU) and evaluated different distance metrics in order to obtain a realistic measure of the border effect within the EU. Our results suggest that the border effect in Europe was previously underestimated due to an excessive simplification when measuring distances. While our preliminary results were similar to previous research, once we applied realistic measures of transports cost (either travel time or generalized transport costs) and removed those countries that are highly affected by the Rotterdam effect, we found that European countries trade 15 times more within themselves than with any other European country. Consequently, integrating the effects of borders in accessibility analysis of international scope evidences that the gap between central and peripheral countries is even larger than expected.

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Vitor Ribeiro, Paula Remoaldo and Javier Gutiérrez

Easy access to public transportation facilities is a critical issue for elderly people, since the elderly rely on public transportation and are one of the more mobility-constrained groups. Yet, the specific factors affecting the accessibility of elderly people to public transportation, such as the slope of streets and the speed at which they walk, are rarely considered in accessibility analysis. The objective of this chapter is to investigate the influence of these factors on the access to public transportation using a geographic information system (GIS). It was concluded that the consideration of the streets’ slopes and the speed at which elderly people walk provides better estimates of the accessibility to bus stops. As a result, transportation-related social exclusion can be measured more precisely, and spatial inequalities are likely to be better understood.

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Pelayo Arbués, Matias Mayor and José Baños

Road transportation infrastructure projects in Spain have been promoted, raising the quality of Spain’s road transportation network to European standards in a short period of time. The objective of this chapter is to measure the output effect of road transportation infrastructure in Spain in the period between 1997 and 2006. In particular we estimate a production function using a panel dataset of Spanish provinces (NUTS 3) in order to account for marginal productivity effects within a province and to document the existence of spillover effects outside the provincial boundaries through the use of spatial econometric methodologies. Road infrastructure endowment indicators are measured using three different indicators: an accessibility measure, the traditional road stock indicators and a variable to accommodate the stock indicator to the degree of utilization. Estimation results show that road transportation infrastructure positively impacts upon the performance of the Spanish economy. The spillover effects of road infrastructure stock and accessibility on neighbouring provinces are larger than direct impacts caused by the infrastructure where it is located.