Suburban collective transit and land use : a methodological approach

In the context of sustainable mobility great attention should be paid not only to urban mobility issues but also to suburban and interurban travels: an efficient collective transit service may represent an alternative to cars for these types of movements. Integrated approaches gathering urban planning and transport management can help in lowering individualized traffic volumes and in increasing collective transit usage. An assessment of the existing transit network and of its catchment areas may be a first step to investigate the relationship between the demand and the supply of collective transit facilities: a focus on land uses can help in providing this first assessment. How can accessibility to collective transit be evaluated? Is it possible to link the suburban collective passenger transit network with land uses, in order to analyse the spatial efficiency of bus stops? The present paper aims at linking the location of existing bus stops with the surrounding land uses, with a focus on the case study of the Province of Brescia, which is one of the most dynamic realities of northern Italy. Using a land use geographical database it is possible to select land uses which, more than others, are able to attract or to generate potential transit users: residential units, public (and of public interest) facilities and productive infrastructures. The area served by the transit service can be estimated as the surface that people can reach from each stop by walking. To a first approximation, an influence radius of 450 m, corresponding to a walking distance of about 10 minutes from each stop, may be chosen and mapped using a GIS software. Then the assessment can be performed calculating the proportion of different land uses covered by the transit service (and by difference the proportion of land uses that are at the moment not served by transit facilities). Furthermore, through an observation of the less covered catchment areas it is possible to detect the less useful bus stops, which in case of a reorganization of the lines may be taken off without generating disagreements. The paper doesn't represent an exhaustive overview of all the accessibility issues related to collective transit but may be seen as a starting point from which further analysis can be developed.