Resumen:
This article presents the development of an application (App) for mobile devices to visualize hotspots in the road network of Madrid metropolitan area, which is also aimed at warning drivers when approaching those hotspots. The paper describes, firstly, the nature of data used and their provenance, and then puts the focus on the Extraction, Transformation and Loading Process (or ETL Process) carried out for the generation of the structured data used by the App. Afterwards, the main features and functionalities of the developed App are also described.