The Series E231 Electric Train in Shonan-Shinjuku-Line Color is one of the most popular suburban commuter trains in the Tokyo metropolitan area. The Shonan-Shinjuku Line is not actually a distinct railway line, but rather a 78 km composite line formed by portions of the Ryōmō Line, Takasaki Line, Utsunomiya Line, Yamanote Freight Line, Yokosuka Line, and Tōkaidō Main Line.