Curitiba is the only city in Brazil that has directed its growth by integrating urban transportation, land-use development and environmental preservation. Since the 1970s Curitiba's administrators have constantly achieved innovations with the city's bus-based transit system through performance and capacity improvements. Originally, the bus system evolved from conventional buses in mixed traffic to busways, which were later fitted with at-level boarding, prepayment and articulated buses, creating the first full bus rapid transit system in the world. Later, the city introduced high capacity bi-articulated buses and electronic fare ticketing systems. In 2009 the integrated bus system was upgraded, again, with the introduction of the Green Line, its sixth BRT corridor which includes the operation of 100 per cent bio-diesel articulated buses. In 2010 Curitiba retrofitted one of the existing corridors, improving its performance to levels that are typical of metro systems. System operation will be further enhanced with advanced traffic management and user information systems.