The train ferries on the Caspian Sea mostly operate as part of China-Europe rail services on the Middle Corridor of the Belt and Road Initiative (BRI). The Middle Corridor is the shortest route between western China and Europe, compared with the more frequently used Northern Corridor through Kazakhstan and Russia. The Middle Corridor offers a projected 14-18 days of transit time, compared with the 19-day journey through Russia. However, the Middle Corridor still has a low capacity, which is currently estimated to be only about 5% of the capacity of the Northern Corridor. The vessels operated on the Caspian Sea have low capacity and there is a shortage of locomotives and wagons in Azerbaijan and Georgia.
As part of the Middle Corridor, ports in Kazakhstan (such as the ports of Aktau and Kuryk) and Turkmenistan (port of Turkmenbashi) are linked across the Caspian Sea to ports in Azerbaijan (Baku in particular). The dedicated rail ferries on the Caspian Sea are operated by Azerbaijan, Turkmenistan, and Kazakhstan government Joint Stock fleets such as the Azerbaijan Shipping Company (ASCo). More than 25 rail ferries are operating on the Caspian Sea. One of the train ferries in operation is the MV Azerbaijan, which has a capacity of 56 railcars. The annual transportation capacity of Caspian ferries is estimated at 95,000 railway wagons or 4.5 million tons of cargo.