Brazilian authorities are evaluating a project to expand the subway network of Rio de Janeiro, with an investment estimated at BRL 28 billion (US$ 5 billion).

The project, which has the support of the federal and state governments, involves the construction of 44 km of lines and 31 stations under a public-private partnership. It includes a tunnel beneath Guanabara Bay. Currently, the subway in the state capital Rio de Janeiro extends for 51km with 41 stations, transporting about 650,000 passengers a day. With the expansion, the system will also reach the cities of Niterói and São Gonçalo in the Rio metropolitan region. 

The federal government's cities ministry will invest BRL 20 million (US$ 3 million) in studies for the subway expansion and the state government will inject BRL 12 million (US$ 2 million). The studies will be carried out by the local economics think tank FIPE. The PPP is expected to last 25 years.