In the last years the transportation infrastructures have experimented a huge development. This has caused a great damage on the natural environment that sometimes is not reversible (loss and isolation of habitats, loss in exchange of genetic material…). The aim of this study is to measure the effect of the transportation infrastructures on the natural habitats that compound the territory of the future National Park "Sierra de Guadarrama". This will serve as a useful tool for the diagnostic of the state of conservation of the area and the implementation of conservation measures. The last objective is to give recommendations for the planning and management of the natural resources in this area. The Guadarrama Range is a very important natural area because of its high natural and cultural values. But this area is also very interesting because of its localisation. Madrid city is only about 40 Km of distance and has a population of about 5 million people. This implies a huge pressure that constantly demands more transportation infrastructures. In this area there are 25 habitats included in the Habitats Directive that compound the 65% of the Madrid Region habitats. These represent 47.832 ha, nearly the 48% of the study area and few less than 22% of Madrid Region. Five of these are priority habitats and represent the 62% of all that are in Madrid. All of these priority habitats are very small and isolated, which is an evidence of its fragility. One of the relevant results of the study is that there is a clear differentiation between those habitats that are located at high altitudes from those that are at lower altitudes. There is a gradient of fragmentation directly related with the altitude. So the loss and isolation of the habitats at high altitudes is lower than at the other ones. This supposes the application of different conservation measures at different scales. Palabras clave: Habitat fragmentation, High-speed railway line, Motorway, Mountain