Marmaray is a high-speed and commuter rail project in the Turkish city of Istanbul. The line has an approximate length of 78 km, it consists of 42 passenger stations, 3 workshops, and 6 traction substations. GPO took part in the preliminary and detailed design phases. The scope includes the design of six traction substations and a temporary substation for the partial opening of the tunnel. This design comprises both the substation equipment and civil works and the electromechanical facilities of the building, including the interface management with the other systems, and the connection with the catenary and energy supplier. The scope also includes the drafting of the technical specifications for the workshop equipment and line maintenance vehicles. It includes the support to the client during the procurement of the equipment and the management of the interfaces with the civil works of the workshops and the electromechanical facilities.