 The SA3 coupler (Soviet Automatic coupler, model 3) used in Russia has several advantages over the Janney coupler used in the United States.The SA3 coupler, while well-designed, has had problems with operating due to being made with lower quality steel, having a low quality of maintenance/repairs/rebuilding, and coupling cars at speeds higher than allowed by the rules.The majority of Russia's rail network uses the 1,520mm Russian gauge, which includes all metro systems and the majority of tram networks in the country.