# Towards Sustainable Regional Planning: Potential of Commuter Rail in the Madrid Urban Region
## 4 Conclusions  
Improving the sustainability of current and future urban regions through unified--or, at least, coordinated--planning and transportation strategies is not new. It is the basis of the TOD concept. Although introduced in the 1990s, researchers still work on how to implement and apply the concept today in different situations around the world [50; 51; 52; 53]. This study proposes that the interaction between a railway station and its surrounding urban area, when understood with network logic and as a system of nodes and places, can serve as a tool to reorient the processes of metropolitan diffusion, structuring a new multicentre system that supports a renewed economic and social vitality and articulates a more sustainable mobility model. To make this tool operational, three categories of analysis are distinguished: municipalities with a commuter station, municipalities without a commuter station, and urban station areas. The analysis of different dynamics (demographic, economic, mobility, etc.) through these categories allows an assessment of the extent of the potential benefits  
Figure 4: Types of station areas based on their capacity for urban expansion in the short, medium, and long terms.  
derived from the presence of a train station, the proximity to the station and the accessibility that the train provides to other urban and metropolitan spaces.  
Based on this interpretation, the Madrid urban region has a powerful commuter rail infrastructure that is currently not used to its full potential and could further contribute to the sustainable development of the region. Now, there is no strategy or policy that identifies the importance of linking urban growth and development with the construction of a regional network of places (commuter stations and their surrounding areas) oriented to public transport (commuter network). This study could guide more-detailed and in-depth studies that, considering other factors and data not available to this research team, could guide not only the development of the areas around the station--investigated in this work--but also the location of future stations and the extension of the rail network based on the actual residential and employment densities as well as those planned by the municipalities. While this paper is being reviewed, a new station is being announced to be built by the Ministry of Transport, Mobility and Urban Agenda in one of the municipalities in the South (Parla) without considering a possible future urban development of the area but the construction of parking and \"kiss and ride\" areas [54; 55].  
There is a need to promote studies that analyse and provide ideas and proposals on how to take advantage of the growth and development potential not only of the areas surrounding commuter train stations on an urban and metropolitan scale, but also of conventional trains in urban areas and rural areas to respond to different current and near-future challenges such as depopulation, sustainable mobility, diffuse urbanization, and urban regeneration.  
Conceptualization, E.S., B.R.-A., A.M., I.M. and J.M.C.; Methodology, E.S., A.M. and I.M.; Investigation, E.S., B.R.-A., A.M., I.M. and J.M.C.; Writing--original draft, E.S.; Writing--review & editing, E.S. and B.R.-A.; Project administration, J.M.C.; Funding acquisition, J.M.C. All authors have contributed to the conception and development of the research, led by [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the MINISTERIO DE CIENCIA E INNOVACION. Proyecto de I+D+I PID2020-119360 RB-100, Railway stations in the mobility of the metropolitan periphery. Towards rail stations 4.0: intelligent and integrated (M = EI\({}^{2}\)).  
Not applicable.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.