China has officially reclaimed the title for world's fastest train. Come September 21, new bullet trains will be blazing their way across China at speeds of up to 400 km/h (248 mph). Consider this China's comeback, after a two-train collision in 2011 that killed 40 people. The top speed at the time was 350 km/h, but authorities throttled them to 300 km/h after the fatal accident.