In the metro of Saint-Petersburg, as in any other, there are tunnels that are not intended for passenger traffic and provide the transfer of trains from one line to another - the so-called Service Connecting Branches.
There are six such places in Saint-Petersburg. Some of them are combined with service points and other tunnel facilities, and some consist of many different tunnels:
- Service connecting branches of 1/2 Lines between 1st Red Line and 2nd Blue Line at stations Технологический Институт-1ru / Технологический Институт-2ru
- Service connecting branches of 1/3 Lines between 1st Red Line and 3rd Green Line at stations Площадь Восстанияru / Маяковскаяru
- Service connecting branches of 3/4 Lines between 3rd Green Line and 4th Orange Line at stations Площадь Александра Невского-1ru / Площадь Александра Невского-2ru
- Service connecting branches of 2/5 Lines between 2nd Blue Line and 5th Purple Line at stations Невский Проспектru / Садоваяru (most commonly used for passenger traffic)
- ССВ 4/5 линий (Садовая/Достоевская)ru between 4th Orange Line and 5th Purple Line at stations Достоевскаяru / Садоваяru (earlier - a section of constant traffic, the only connecting branch in St. Petersburg of two independent tunnels)
- ССВ 1/6 линий (Путиловская, строится)ru between 1st Red Line and 6th Brown Line at stations Нарвскаяru and Путиловская (строится)ru
Accordingly, Садоваяru is the only station in Saint-Petersburg with forks of railway tracks on both sides.