# Towards Sustainable Regional Planning: Potential of Commuter Rail in the Madrid Urban Region
## 3 Results and Discussion
### The Urban Development Potential of the Commuter Station Areas
Considering the developable and potentially developable land, Figure 4 shows a classification of station areas with different capacities for urban growth in the short, medium, and long terms: (i) Type I has low capacity for urban expansion (<50 ha of developable and <50 ha of potentially developable land); (ii) Type II has medium-low growth potential (50-100 ha of developable and 50-100 ha of potentially developable land); (iii) Type III has limited possibilities to develop in the short and medium terms (<100 ha of developable land) and greater options in the long term (>100 of potentially developable land); (iv) Type IV, just the opposite, has greater options in the long term (>100 of developable land) but limited possibilities in the short and medium terms (<100 ha of potentially developable land); and (v) Type V has great development potential now and in the future (>100 ha of developable land and >100 ha of potentially developable land). This classification and the corresponding data show there is a lot of growth potential in the short and medium terms (predominance of Type IV) around many stations that are close to Madrid municipality along the south and east lines. If a coordinated urban and transportation strategy--both at the municipal and metropolitan scales--is established considering the existing urban land and the developable and potentially developable land in the areas around commuter railway stations, there is a lot of room for progress towards a more polycentric and more sustainable urban and regional development. In this sense, urban planning should ensure that new urban growth meets the density, compactness, and land use mix criteria. The urban areas around stations are the drivers of mobility. Therefore, the way in which the management and characteristics of land uses are established could make the commuter rail network more sustainable from environmental, social, and economic perspectives. This could facilitate an increase in investment in public transport, making it more competitive and convenient than other modes of transport that are less sustainable. More trains and more services, more buses and routes within the station areas, and a better-designed public space are needed. It would be desirable that this combined strategy consider the whole urban region. However, other possibilities could be easier to coordinate and promote. Partial strategies by commuter rail lines would be very useful also--e.g., the _contrats d'ave_ (axial agreements) implemented in France along the transit axis [49]. Municipalities with commuter stations along a common axis, by areas or for the whole urban region, could collaborate to promote, lead and coordinate new strategies and policies to maximize the development potential they represent, for example, promoting urban growth in station areas in the face of dispersion, launching mobility plans and designing public space in station areas, developing urban rehabilitation and regeneration policies to upgrade designs that are obsolete in physical terms and outdated in social terms or promoting commuter train stations as spaces for businesses, tourism, retail and education activities in the urban areas around the stations.