Buenos Aires has recently opened a bus rapid transit system, the Metrobus. The system uses modular median stations that serve both directions of travel, which enable pre-paid, multiple-door, level boarding. The first line, opened on 31 May 2011, runs across the Juan B. Justo Ave has 21 stations. The system now has 4 lines with 113 stations on its  network, while numerous other lines are under construction and planned.