山田線
After the opening of the Yamada Line, passenger trains travelling between Morioka and Miyako became so congested that it was often impossible to sit down and people had to stand up on the trains. Prior to the final extension of the Kamaishi Line in 1950 to Kamaishi, the Yamada Line was the only direct line between the coast and the inland areas of northern Iwate, and upon the extension of the Yamada Line to Kamaishi by 1939, freight traffic began using the Yamada Line throughout the day and night, as it formed the sole rail connection between Kamaishi and the Tohoku Main Line.