The masterplan line shall connect passengers from Sucat station in Muntinlupa to either the Batangas International Port, Legazpi, Albay, or Matnog, Sorsogon.

The line was to be partially operable between San Pablo and Lucena by 2025, and the first phase between Banlic and Daraga would be fully opened by 2027.

[12] Several more segments were constructed into Quezon province and the Bicol Region, including a new line called the Legazpi Division.

[13] On May 8, 1938, the two sections were officially linked with President Manuel L. Quezon hammering the golden spike at Del Gallego, Camarines Sur.

[19] During the enhanced community quarantine in Luzon, the South Main Line was used to carry so-called locally-stranded individuals or people stranded outside their hometown during the lockdowns.

The causes of the project's delay include affected informal settlers, a lack of construction and funding, and the relocation of families, which began in October 2023.

[40] In the following month, Bicol Saro party-list Rep. Brian Raymund Yamsuan announced that Japan would be viable to fund the project.

[41] In July of that year, it was revealed that it may likely end up borrowing from the ADB and Asian Infrastructure Investment Bank (AIIB) to rebuild the Bicol Express through the SLH.

[7] In August, NEDA Secretary Arsenio Balisacan said it could be that the World Bank, ADB, Japan, India, and Korea have offered the project.

[8] In January 2025, however, according to an interview on Ted Failon at DJ Chacha sa True FM, Jeremy Regino, the DOTr undersecretary for railways, said the project could not have funding yet.

[42] He said the DOTr failed to secure enough funding in the 2025 General Appropriations Act (GAA) to undertake the preparatory works for the project, making it challenging to acquire the right of way.

[43] In April 2024, the government announced the Luzon Economic Corridor, a plan to link the ports in Subic, Clark, Manila, and Batangas and build an industrial area free of slow traffic and powered by renewable energy, positioned to rival the capital in economic output, and a freight railway that will connect the four ports, further postponing the development of the South Long Haul, and a spur linking to Batangas province is now absorbed by the new railway.

[46] On April 21, the Presidential Commission for the Urban Poor-Luzon along with the Department of Transportation and local governments held a conference regarding the identification of affected private property and resettlement of households whose houses are located on the right-of-way of the line.

[47] On May 7, the Philippine Railways Institute published the latest map for the project that was initially approved by the Department of Transportation on March 31.

Unlike the old line however, there will be no level crossings in favor of full grade-separation with 397 of such interchanges between Alabang and Legazpi stations will be eliminated as a result.

Two hundred thirty bridges and viaducts shall comprise a total length of 51.3 km (31.9 mi) or 12.94% of the proposed right-of-way.

[66] Meanwhile, the use of an eight-car trainset was announced by the PNR through a press conference with Legazpi City mayor Noel Rosal on March 5, 2021.

[52] By June 30, CRDC made its basic design report public and specified that the 8-car trainsets will be used for both long and short-distance local train services.

[59] On January 18, 2022, Chinese Ambassador Huang Xilian's Facebook page unveiled the second iteration of the diesel multiple units.

The new passenger stock is based on the KTM Class 61 meter-gauge DMUs built for the Malaysian Keretapi Tanah Melayu adopted to standard-gauge track.

[68] China Railway's HXN series diesel locomotives has been proposed for the line's freight services according to the June 2021 report.

[26] There were also much earlier plans in 2014 to electrify the proposed Batangas branch line once the North–South Commuter Railway's southward extension (NSCR South Phase 2) has been approved.

According to a 2015 Japan International Cooperation Agency study, the demand for intercity rail is expected to only reach 25,000 one-way trips per day by 2039.

This means that there is not enough passenger traffic in the area to justify the construction of an electrified line in the level of the NSCR, let alone high-speed rail in the near-future.

[71] In 2019, DOTr Undersecretary for Railways Timothy John Batan stated that projects such as the South Long Haul were developed with eventual HSR construction in mind.

Some parts of Banlic station and its northward extension to Sucat under Phase 4 will be built over private property, which is caused by the present Metro Commuter right-of way being superseded by the NSCR South.

The new Naga station for example was built 1.77 km (1.10 mi) southeast of it old location in Barangay Tabuco both to avoid causing traffic in its city center and to loosen its railway curvature.

Additionally, even though South Long Haul and NSCR trains will overlap on the present PNR right-of-way between Muntinlupa and Calamba, the two lines will not share tracks.

PNR general manager Junn Magno stated in a February 2021 interview with Motoring Today that he intends to use the line to connect the Manila North Harbor and the Batangas International Port.

[81][82] The at-grade reconstruction will only cover the section between Solis and Sucat, with the South Long Haul proper being rebuilt to solely standard gauge.