Currently, Japan's train system has two world records. One is the world's longest train bridge, the Seto Ohashi Bridge. This bridge is actually a long string of connected bridges across the water when going from Okayama Prefecture on Honshu to Kagawa Prefecture on Shikoku Island
. The bridge was opened in April 1988 and is a total of 9,368 meters long. There's even a space on this bridge for shinkansen tracks, whenever the time comes.
(By the way, the other world record is the world's longest train tunnel, the Seikan Tunnel, which connects Aomori with Hokkaido.)