Throughout the last decades, light rail transit systems (LRT) have been built around the world due to their strengths: regularity, savings in CO2 emissions, flexibility, image and optimization of urban space. This research proposes the analyses of a group of LRTs by using a method supported by GIS. Some data and parameters have been stated in order to define the systems. The range of values obtained allow us to characterize the LRT systems operating in Spain: for instance, mean distance range between stations is 405 m to 685 m, and potential users range (people who live no more than 500 m from a station) is 18,000 to 30,000, and population density in the capture areas is never below 1514 pop/km2 (in cities with no metro system). The benefit of the present study is to establish common data values that could be useful in future studies and preliminary projects carried out in other Spanish cities interested in introducing an LRT in their urban grid, and also for comparison with LRT in other countries. The method could be also applied to other public transportation systems, and to other countries.