Carrying out European financing infrastructure projects in Bulgaria since 2003, Doğuş Construction won another major project contract in the country. The contract for the DVU21 JV led by Doğuş Construction includes the 8.43 m diameter TBM tunnels of the 6 km long metro line that will expand Sofia Metro Line III to the Regional Hospital through Geo Milev and Slatina.

This will be the fourth major project in Bulgaria after Trakia Motorway, Section between Karnobat-Burgas, Lot 5, Sofia Metro Extension Project, Line II Lot 1 and Sofia Metro Extension Project, Line III Lot 4. With the project significantly reducing urban traffic, Doğuş Construction will increase its share in Sofia Metro tunnel construction to 16 km. With this project, 90 percent of the total line length of the TBM metro tunnel in Sofia will be the signature of Doğuş Construction. The project has been scheduled to be completed in the second half of 2026.