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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2009.12.013 Byline: S. Mancebo Quintana (a), B. Martin Ramos (a), M.A. Casermeiro Martinez (b), I. Otero Pastor (a) Abstract: The aim of the present work is to design a model for evaluating the impact of planned infrastructures on species survival at the territorial scale by calculating a connectivity index. The method developed involves determining the effective distance of displacement between patches of the same habitat, simplifying earlier models so that there is no dependence on specific variables for each species. A case study is presented in which the model was used to assess the impact of the forthcoming roads and railways included in the Spanish Strategic Infrastructure and Transport Plan (PEIT, in its Spanish initials). This study took into account the habitats of peninsular Spain, which occupies an area of some 500,000 km.sup.2. In this territory, the areas deemed to provide natural habitats are defined by Directive 92/43/EEC. The impact of new infrastructures on connectivity was assessed by comparing two scenarios, with and without the plan, for the major new road and railway networks. The calculation of the connectivity index (CI) requires the use of a raster methodology based on the Arc/Info geographical information system (GIS). The actual calculation was performed using a program written in Arc/Info Macro Language (AML); this program is available in FragtULs (), a set of tools for calculating indicators of fragmentation caused by transport infrastructure (http://topografia.montes.upm.es/fragtuls.html). The indicator of connectivity proposed allows the estimation of the connectivity between all the patches of a territory, with no artificial (non-ecologically based) boundaries imposed. The model proposed appears to be a useful tool for the analysis of fragmentation caused by plans for large territories. Author Affiliation: (a) Transport Research Center (TRANSyT), Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid, Spain (b) Department of Soil Science, Faculty of Pharmacy, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain Article History: Received 14 July 2008; Revised 10 September 2009; Accepted 9 December 2009