​Today, a quarter of the world’s population lives in urban “agglomerations”—supersized metropolitan areas that cut across jurisdictional boundaries and bring together one or more cities along with…

Ede Ijjasz-Vasquez, Philip E. Karp, Maria Angelica Sotomayor |

Follow the authors on Twitter: @danpulido and @IrenePortabales   A branded metro station in Madrid Most metro systems around the world are unable to cover their operating costs with fare box…

Daniel Pulido, Irene Portabales González |