While the former Soviet Union got a late (and slow) start with rail electrification in the 1930s it eventually became the world leader in electrification in terms of the volume of traffic under the wires. During its last 30 years the Soviet Union hauled about as much rail freight as all the other countries in the world combined and in the end, over 60% of this was by electric locomotives. Electrification was cost effective due to the very high density of traffic and was at times projected to yield at least a 10% return on electrification investment (to replace diesel traction). By 1990, the electrification was about half 3 kV DC and half 25 kV AC 50 Hz and 70% of rail passenger-km was by electric railways. Comparison to the US and others Compared to the US, the Soviet Union got off to a very slow start in electrification but later greatly surpassed the US. Electrification in the US reached its maximum of 5,000 km in the late 1930s which is just when electrification was getting its start in the USSR. About 20 years after the 1991 demise of the Soviet Union, China became the new world leader in rail electrification with 48,000 km electrified by 2013, and continuing to grow. History 1920s: Lenin supports rail electrification Replacing steam traction (on lines with high traffic) by electrification was cost effective and this was the impetus for the first electrifications in the 1930s. The 1920 national electrification plan, GOELRO—ГОЭЛРО included railway electrification and was strongly supported by Lenin, the leader of the Soviet revolution. Lenin wrote a letter implying that if rail electrification was not feasible at the present time, might it not be feasible in 5–10 years from now. And in fact, railway electrification actually got started several years later but Lenin didn't live to see it happen. In 1926 a 19 km long section from Baky, electrified at 1200 VDC, was opened for commuter motor-car trains. In 1929, a 18 km section, electrified at 1500 V was opened from Moscow to Mytishchi. Future electrifications in the 1930s would be more substantial and mostly at 3000 VDC (3 kV). 1930s Some new electrification at 1.5 kV still continued but in the 1930s over three times as much electrification used 3 kV. Mainline railway electrification at 3 kV. in the Soviet Union began in 1932 with the opening of a 3,000