# Towards Sustainable Regional Planning: Potential of Commuter Rail in the Madrid Urban Region
## 3 Results and Discussion  
### Urban Expansion and Mobility Patterns in the Madrid Urban Region  
In the last six decades, the Madrid urban region has increased its population by 5.5 million; this demographic growth has established it as one of the densest regions in Spain and Europe, reaching 508 inhabitants per km\({}^{2}\) in 2018. During this period, the artificial surface grew by 1360.1 km\({}^{2}\). However, the way in which the territory is occupied has changed from denser and more compact forms to less dense and more dispersed forms, thus increasing the urban footprint per inhabitant. In this sense, the proportion of urban land area per inhabitant increased from 65 m\({}^{2}\) per capita in 1956 to 203 m\({}^{2}\) per capita in 2018 (Table 2). In parallel to this process of land occupation, increasingly fewer sustainable travel patterns are unfolding. According to the data provided by the Mobility Surveys by COPLACO in 1974 and by CRTM in 2018, mobility by private vehicle has increased from 23.0% to 39.0%, while travel on foot has decreased from 47.2% to 34.0%, and travel by public transport has \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **1956 1** & **1990** & **2000** & **2006** & **2012** & **2018** \\ \hline Population & 1,823,410 & 5,367,573 2 & 5,682,617 & 6,606,673 & 7,222,115 & 7,301,569 \\ Base index 100 = Year 1990 & & 100 & 106 & 123 & 135 & 136 \\ Artificial surface or urban land & 118.5 & 704.6 & 1036.0 & 1312.2 & 1482.1 & 1478.6 \\ Base index 100 = Year 1990 & & 100 & 147 & 186 & 210 & 210 \\ Density in the Madrid urban & 227 & 373 & 395 & 459 & 502 & 508 \\ region (inhabitants per km\({}^{2}\)) 3 & & & & & & \\ Proportion of area per & 65 & 131 & 182 & 199 & 205 & 203 \\ inhabitant (m\({}^{2}\) per capita) & & 100 & 139 & 151 & 156 & 154 \\ Base index 100 = Year 1990 & & & & & & \\ \hline \hline \end{tabular}  
* 1: Evolution de la Coupacion del Suelo en la Comunidad de Madrid (Evolution of Land Use in the Community of Madrid) (1956–2005), prepared by the General Directorate of Urbanism and Territorial Strategy, Department of the Environment, Housing and Land Management of the Community of Madrid. 2: 1991 Census. There are no population data as of 1990. Starting in 1996, there are census data for every year. 3: The area of the Madrid urban region is 14,380 km\({}^{2}\).  
\end{table} 
Table 2: Evolution of the population and artificial surface of the Madrid urban region in selected years. Source: National Center for Geographic Information and National Institute of Statistics of Spain. decreased from 29.9% to 24.3%. Table 3 shows that, from 1988 to 2018, travel by public transport decreased considerably, while motorized mobility by private transport increased, increasing levels of congestion, especially after the economic crisis [47]. If we consider the evolution using the base index = 100, the relative indicator for the number of trips per day is considerably higher than that for jobs and population, which highlights the spatial mismatch in the location of jobs and the location of the population. This mismatch is the result of several factors; among them, notably, is that the labour market and the housing market obey different logics, and the current urban framework covers a city production process based on the low density and compactness and the high specialization of the built spaces. A reality that is also palpable is the increase in the number of vehicles per capita, increasing from 0.39 in 1988 to 0.74 in 2018, and the number of trips per day and per capita, increasing from 1.29 in 1988 to 1.61 in 2018. Although it has not been possible to obtain disaggregated data at the municipal level, the Household Mobility Surveys provide information on the evolution of trips by mode of transport between areas (Figure 1 and Table 4). In the city of Madrid, the trend shows an increase in active mobility (on foot and by bike), a slight reduction in the use of public transport and a significant decrease in the use of private transport.