# A GIS-Based Analysis of the Light Rail Transit Systems in Spain
## 2 Literature Review
In Spain, the Observatorio de la Movilidad Metropolitana [Polytechnic University of Madrid Mobility Observatory] has collected some valuable data, mainly from the transportation companies themselves [53]. Economic analyses have also been carried out [54], and some lines have been the subject of previous studies, such as the LRT in Granada [55; 56; 57], which included details such as population density near stops among other parameters related to transit-oriented development (TOD) analysis. On another matter, the use of Geographic Information Systems for transportation system analysis has become generalized. Thus, use of GIS has recently been gaining in strength for the study of capture areas [58; 59]. A station's capture area may be definedas the urban space or territory that potential users are going to come from. Traditionally, citizens have been thought to be willing to walk a maximum time or distance from their homes or trip's point of origin to a public transportation station and the capture area is the space between the station and the limit of that time or that maximum distance. Studies have shown the complexity of defining that capture area for a specific station, as many parameters enter into it, such as demographic [60] or urban design characteristics [61; 62; 63], and therefore, there are specific methods for determining exactly what this area is at a particular station, such as surveys [64] or ride cards [65]. However, in macroanalyses related to planning or a complete transportation system, the area is usually reduced to the portion of the city included within a circle with its center at each station in the system. This simplification requires, in turn, setting the radius of each circle, and in the literature, for LRTs this would vary from 400 m or 0.25 miles [66; 67] to 800 m [68; 69], although it is accepted that in the outskirts, citizens are willing to go further [70]. We might note that, in Spain, the usual distance is 500 m [56; 71]. Beyond the capture areas, the GIS has also been used to acquire data on the density of stops or stations [72; 73], stop spacing [74], land use [75] or road lengths [76]. Furthermore, GIS has be used to ascertain the \"attraction nodes\" (e.g., offices, tourist attractions, and hotels) within a broad area [77] or to identify the hotspots of the healthcare services in a territory [78], and GIS applications pertinent to the field of transportation engineering were developed [79] to analyze the impact of activity trips on regional transportation patterns. Moreover, some researchers have used GIS for developing multicriteria studies linked to public transport or even light rail system topics. [PERSON] and [PERSON] analyzed the appropriateness of parking site selections around LRT stations for the customers [80]. [PERSON] et al. [81; 82] used GIS as a tool for their development of a transportation model between Beijing and XiongAn. It has therefore been shown to be a useful tool for finding parameters related to transportation networks. In brief, LRT systems are in ascendant in numerous countries. The main advantages have been established; moreover, the existence of failed projects has been well described, regularly linked to problems related to urban and LRT scheme geometry, as stations. Furthermore, research on the description of LRTs through parametrical characterization has been carried on in different occasions; finally, the rise of GIS for developing research on transportation systems, and in particular on urban geometry in the stations surroundings is a fact. For that, research on Spanish LRTs for characterizing the ongoing schemes through the determination of the values of different parameters and ratios, linked to urban geometry and users' densities in the catchment areas can be interesting. An expected benefit is the determination of values for helping authorities and planners to develop future projects; moreover, current schemes may be analyzed in order to establish possible explanation of their success or failure.