marta operates buses and a subway system in the city of atlanta, fulton, clayton and dekalb counties, while cobb and gwinnett counties operate their own independent suburban transit systems that feed into marta. this is a result of those counties' refusal to join the marta system (although gwinnett is holding a vote in march 2019 to possibly join marta again), a situation which was originally closely related to white flight from the city. it is the only us system in which the state does not provide any funds for operation or expansion, instead relying entirely on a 1% sales tax in its three counties. due to the passage of a 1% sales tax in clayton county on november 4, 2014, marta replaced the defunct c-tran system bringing buses and commuter rail to the county beginning march 2015, with full bus service in 2016. the atlanta streetcar, a light rail loop, connects centennial olympic park and marta heavy rail subway to the sweet auburn district and points in between. xpress ga, a suburban commuter bus service operated by the georgia regional transportation authority or grta, has over 32 routes running from the suburbs and exurbs to downtown atlanta in 12 metropolitan counties.