Kansas City International Airport, airport code MCI (Mid-Continent International Airport) was built to TWA's specifications to make a world hub. Its original passenger-friendly design placed each of its gates   Like most American cities, Kansas City's mass transit system was originally rail-based. From 1870 to 1957, Kansas City's streetcar system was among the top in the country, with over of track at its peak. The rapid sprawl in the following years led this private system to be shut down. On December 28, 1965, the Kansas City Area Transportation Authority (KCATA) was formed via a bi-state compact created by the Missouri and Kansas legislatures. The compact gave the KCATA responsibility for planning, construction, owning and operating passenger transportation systems and facilities within the seven-county area. In July 2005, the KCATA launched Kansas City's first bus rapid transit line, the Metro Area Express (MAX). MAX links the River Market, Downtown, Union Station, Crown Center and the Country Club Plaza. MAX operates and is marketed more like a rail system than a local bus line. A unique identity was created for MAX, including 13 modern diesel buses and easily identifiable "stations". MAX features (real-time GPS tracking of buses, available at every station), and stoplights automatically change in their favor if buses are behind schedule. In 2010, a second MAX line was added on Troost Avenue. The city is planning another MAX line down Prospect Avenue. The Prospect MAX line launched in 2019 and Mayor Quinton Lucas announced the service would be fare-free indefinitely. On December 12, 2012, a ballot initiative to construct a $102 million, 2-mile (3200 m) modern streetcar line in downtown Kansas City was approved by local voters. The streetcar route runs along Main Street from the River Market to Union Station; it debuted on May 6, 2016. A new non-profit corporation made up of private sector stakeholders and city appointees – the Kansas City Streetcar Authority – operates and maintains the system. Unlike many similar systems around the U.S., no fare is to be charged initially. Residents within the proposed Transportation Development District are determining the fate of the KC Streetcar's southern extension through Midtown and the Plaza to UMKC. The Port Authority of Kansas City is also studying running an extension to Berkley Riverfront Park. In 2015, the KCATA, Unified Government Transit, Johnson County Transit, and IndeBus (all separate metro services) began merging into one coordinated transit service for the Kansas City region, called RideKC.