 On February 6, 2017, Metro confirmed the accelerated retirement of the 4000-series cars due to their many reliability concerns.According to WMATA, "The 4000-series rail cars were by far Metro's least reliable, traveling an average of only 27,259 miles between delays.By contrast, the best performing cars, the 6000-series, are nearly four times more reliable, traveling more than 103,000 miles between delays."