Accessibility and Socio-economic Activities Location
A Nuzzola, P Coppola, University of Rome "Tor Vergata", IT
The paper aims at analyzing to what extent differentiated changing accessibility within an extended area affects the distribution of residential and economic activities. The study is carried out by mean of empirical and modelling analyses.
That land use and transport are closely inter-linked is common wisdom among planners and the public. The analysis of the impacts of land-use on the transportation system is well-established (as well as the modelling approaches), on the other hand, the reverse impact from transport to land use, is less well known. In facts, in the literature there exists a number of studies investigating the impact of transport on Land use. However, these are mainly based on simulation results, very few of them are based on empirical analysis and observed data. One reason for this may be the fact that land use changes occur much more slowly than changes of travel behaviour and are subject to many other influences other than transport, such as population growth, economic development changes in lifestyles, household formation, consumption patterns and production technology and are therefore difficult to isolate (Wegener and Furst, 1999). Moreover most of these studies have been carried for urban areas, very few have focused on the regional or metropolitan scale.
This paper aims at analyzing to what extent changing accessibility affects the distribution of residential and economic activities within an extended area (e.g. a region or a metropolitan area). The study is carried out by mean of empirical and modelling analyses. The case study is that of the metropolitan area of Naples, one of the most populated in Italy with about 4 millions of residents, including the very congested municipalities and zones with densities above the 10.000 inhabitants per squared Km. This case study is of particular relevance since after a big earthquake in year 1980, which destroyed cities and transport infrastructures, there was a large investment in the reconstruction, particularly of the new regional road network. Therefore, it is expected that the effects due to the changes in accessibility (which occurred in a small number of years) can be isolated and utilised for the scopes of our analysis.
The empirical study consists of before-and-after analyses correlating the variation of zone accessibility to the variation of population and other economic activities (Commerce, services, etc) over a 20 years long period, using the Census data (1981, 1991, 2001, 2006) and the available transportation data. The results of this analyses show that the impact of accessibility on the location of certain economic sectors is negligible (e.g. for Public services, Wholesale), while it is significant for Residents, Retail, Private Services location. In the latter case, however, it is evident that there are other factors affecting such location choice even stronger than accessibility (e.g. housing prices, congestion of the urban system, and so on). In order to deeper investigate such issues, an integrated modelling framework simulating land-use and transport interaction is proposed. The overall modelling framework consists of :
a transport model which allows to estimated the Origin-Destination generalised travel cost and the (active and passive) accessibility of each zone, as well as other transportation network performances;
the residential location model which estimates the distribution of residents by zones within the study area;
the activities location model which estimates the distribution of the economic activities among the zones of the study area.
The three sub-modules are strictly interrelated and the general equilibrium problem is solved by means of an iterative procedure base on the Method of Successive Averages (MSA). The results of the calibration and of the application of model to the case study of Naples are presented and discussed in the paper.
Association for European Transport