On May 24th, 1960, the Beijing-Ulaanbaatar-Moscow K3/4th international passenger train was officially launched. This is the first international intermodal train since the founding of New China. It spans the Eurasian continent and passes through China, Mongolia and Russia, with 33 stops, with a total length of 7,858 kilometers, and stops in the capitals of the three countries. One-way train operation takes about 132 hours, and the round trip takes 13 days. Trains even have to run in the ultra-low temperature environment of MINUS 50 degrees Celsius in winter, which brings many technical challenges to the development of trains. With the withdrawal of many "green leather cars" in China, K3/K4 "green leather cars" galloping in China and Russia finally ushered in the reconstruction after upgrading from 1996.