In 1999, the former Line 4 was to be located between Recto Avenue in Manila and Batasan Hills in Quezon City.

[2][3] An unsolicited proposal for the project was submitted to the Philippine government by Malaysia-based construction engineering company AlloyMTD group in 2016,[4][5] and is awaiting approval by the National Economic Development Authority (NEDA).

According to MTD Philippines, Inc. President Patrick Nicholas David, the project would cost ₱60 billion.

[8] Another proposal, from the MRT-7, as part of its future expansion, will tread the same path with the exception of starting from West Avenue onwards towards Pier 4, instead of Quiapo.

However, MRT-7 has already began construction works along West Avenue for its turnback tracks, and the guideway is the possible starting point of its proposed expansion.