Experimentation
In the late 1920s, the UIC had established a working group for the replacement of the chain link coupler, which restricts the efficiency of freight railroads in a major way. Many railroads ran prototypes. In Germany, coal trains with Scharfenberg couplers yielded unfavourable results in winter weather, other railroads did similar tests. But the UIC was not able to agree on one replacement. This failure of the UIC, which hampers freight operation in Europe even today, led to the decision by the Soviet Union to move forward without a standard being achieved in the talks.
The coupler was named SA-3. This type of coupler was standardized for the railways in the Soviet Union after World War II.
Further tests were carried out in the 1950s.
Read more about this topic: SA3 Coupler