Japan has started testing its fastest-ever bullet train -- capable of reaching 400 kilometers per hour (249 mph) -- as it continues to develop the revolutionary mode of travel.

The ALFA-X version of the Shinkansen train began three years' worth of test runs on Friday.

Once it enters operation sometime around 2030, it will run at speeds of up to 360 kph (224 mph), comfortably making it the world's fastest bullet train. It will also outpace China's Fuxing train, which runs at 10 kph slower despite being designed with the same top speed capabilities as the ALFA-X.

Although the Alfa-X holds the title of the world’s fastest train right now, it may already be dethroned by the time it goes into service. That’s because a new maglev line is being built between Tokyo and Nagoya with operations starting in 2027. Traveling mostly through deep tunnels, the magnetically levitated train will travel at a top speed of 505 kilometers per hour, cutting the time between the two cities to 40 minutes, from the current 110 minutes.