Moscow Central Diameters

The Moscow Central Diameters (MCD) (Russian: Московские центральные диаметры (МЦД), romanized: Moskovskiye tsentralnye diametry (MTsD)) are a system of passenger rail transport lines in the Moscow agglomeration, created on the basis of the existing Moscow railway infrastructure. In the media and ad campaigns, the project is also widely called a "above-ground metro" (City media refer to it as part of the Moscow Metro), although by definition of characteristics and technical equipment it is not one. Despite being a separate system, the MCD is integrated with the metro by a single fare payment system, similar to other urban electric railways such as the Berlin S-Bahn system or the Paris RER.

The MCD connect Moscow and the cities of the Moscow region: Lobnya, Dolgoprudny, Odintsovo, Krasnogorsk, Podolsk, Zelenograd, Khimki, Lyubertsy, Ramenskoye, Balashikha and Aprelevka. The first two diameters with a total length of 132 km and 60 stations in the mixed open traffic schedule were opened on November 21, 2019. The third diameter was opened on August 17, 2023, and the fourth on September 9, 2023.