Of the railroad route connecting Tokyo with Naoetsu in Niigata Prefecture (later known as the Shin'etsu Line), the 11.2-km section between Yokokawa and Karuizawa Stations was built under the technical guidance of the United Kingdom in 1893 and was called the Usui Line. There were 18 bridges and 26 tunnels on the Usui Line. The Meganebashi Bridge on the Usui River was the largest bridge of them all. The quadruple arched bridge was designed by Charles Assheton Whately Pownall, a British engineer who was invited to head the Railroad Construction Bureau by the Japanese Government at the time. The bridge is approx. 91 meters long and 31meters high. It is estimated that two million bricks were used to make it. The No. 2, 3, 4, 5, and 6 bridges still remain intact to this day, all of which were made with bricks and are now designated nationally important cultural property.
The Abt System was replaced with a new railroad system when the construction of a new railroad route was completed in 1963. In 1993, the Abt System became a nationally designated important cultural property as a cultural asset that sustained the modernization of Japan. In 2001, a nature trail was built where the old disused railways were. It was named Abt Road. Today, there is a 6-kilometer nature trail between the old Yokokawa and Kumanodaira Stations. Along the Abt Road, there are many scenic spots, including the old Maruyama Substation, which is another nationally designated important cultural property, three brick bridges, and ten tunnels. It is a place where you can experience the Usui Pass railroad heritage. The series of railroad brick buildings, represented by the Meganebashi Bridge, are worth seeing. Lake Usui along the Abt Road is beautiful in the fall with its colored leaves.