In 1970, the Soviet Union began a smooth change of the track gauge from 1,524 mm to 1,5200 mm. This process lasted over 20 years, until the early 1990s. Various official sources indicate that the aim for the change was to increase the stability of the railways when operating freight trains, increasing their speed.

Russia utilizes a "broad gauge" of 1520 mm (originally 1524 mm), which is wider than the standard 1435 mm used in most of Europe and North America. This dates back to the mid-19th century when Tsar Nicholas I commissioned American engineer George Washington Whistler to build the Saint Petersburg–Moscow Railway. Whistler recommended the 5-foot gauge, which was then common in the Southern U.S., arguing it offered better stability and higher load capacity. While a popular myth suggests the different gauge was chosen primarily to prevent invading armies (like Napoleon's or later Hitler's) from using the Russian rail network, historians largely agree the choice was based on technical and economic superiority at the time. Today, this legacy persists across the former Soviet states, creating a "break of gauge" at borders where trains must either switch wheelsets or passengers must transfer.