The four-station extension will eventually form part of the northern section of the 28km Grand Paris Blue Line and will relieve Line 13 north of St Lazare, which is one of the most congested sections of the Paris Metro.

The plans will be submitted to the boards of Ile de France Transport Authority (STIF) and Paris Transport Authority (RATP) in December and construction should begin on the €1.2bn project in late 2013 with commissioning scheduled for 2017. The project includes construction of a new depot north of Clichy St Ouen RER station.

Public consultation is also now underway on the southern section of the orbital Red Line.