The work comes under two contracts, one for €70m and another for €169m. This second phase includes the construction of five stations and a bus terminal.
Line 4, known as the Yellow Line, connects downtown São Paulo to the southwest of the city and will serve nearly a million passengers a day.
The larger contract includes the underground construction of the Villa Sonia station. Rail access to the new station will require the completion of a 1.85km tunnel to be built by the New Austrian Tunnelling Method.