Line A was inaugurated on 4 November 1910, after being postponed because of floods in January that year. Line B was inaugurated on 26 February 1911. Because of the high construction costs, the construction of line C was postponed. Nord-Sud and CMP used compatible trains that could be used on both networks, but CMP trains used 600 volts third rail, and NS −600 volts overhead wire and +600 volts third rail. This was necessary because of steep gradients on NS lines. NS distinguished itself from its competitor with the high-quality decoration of its stations, the trains' extreme comfort and pretty lighting.