The 24km White Line would extend the metre-gauge system beyond the current terminus of the South Line at Parnamirim to São José do Mipibu and Nísia Floresta.
The project is estimated to cost Reais 152m ($US 40.2m), including the acquisition of three additional diesel LRVs.
CBTU says Brazil's Ministry of Cities will need to approve the project and provide financial backing if development of the scheme is to continue.
