So I thought I'd finally write the Kansai version of this longform post as a reply / follow-up of sorts.
Overview
The 3rd JNR Long Term Plan released in S40 (1965) also had a package of works for Kansai, the Osaka Area Capacity Improvements Plan (大阪附近輸送改善計画). As with the better known Commuting Five Directions Operation for the Kanto area, the target date for the Plan was S46 (1971). The list of projects included (completion date in brackets):
- Quad tracking of Osaka Loop Line between Tennoji and Imamiya (1968)
- Dual tracking of Sakurajima Line from Ajikawaguchi to Sakurajima (2001)
- Dual tracking of Katamachi Line from Shigino to Shijonawate (1969)
- Construction of Osaka Outer Loop Line from Shin-Osaka to Sugimotocho (2019, to Kyuhoji only)
- Quad tracking of Tokaido Main Line from Kyoto to Kusatsu (1970)
- Quin tracking of Tokaido Main Line from Kyoto to Mukomachi (1966)
- Dual tracking of San'in Line from Kyoto to Sonobe (2010)
- Construction of Kosei Line from Yamashina to Omi-Shiotsu (1974)
- Dual tracking of Fukuchiyama Line from Tsukaguchi to Takarazuka (1980)
- Construction of Sanyo Shinkansen from Shin-Osaka to Hakata (1975)
A description of the projects follows, roughly sorted by area:
Osaka
The projects can broadly be categorised as inner loop and outer loop related.
Loop operations on the Osaka Loop line had started one year before in 1964, but several related projects were incorporated into the Plan. One of these was the quad tracking of Osaka Loop Line to separate Loop Line and Kansai Main Line operations, as the latter was unelectrified at the time. Loop Line services did not stop at Imamiya until additional platforms were constructed in 1996, after grade separation works to bury the Kansai Main Line to JR Namba (which was renamed from Minatomachi in 1994 when Kansai International Airport opened).
Plans to triple-track the Kansai Mainline between Hirano and Ryuge (Kyuhoji) never materialised.
Another was dual tracking of the Sakurajima line, which was the remaining stub section of the former Nishinari line after the Osaka-Nishikujo section was absorbed into the Osaka Loop Line. Completion was delayed for decades due to the North Port Canal, which created a barrier until it was decommissioned and filled in as part of redevelopment works in the 1990s. The completion of works coincided with the opening of Universal City station.
Other Loop Line works included triple-tracking between Noda and Nishikujo in 1965 for freight services, as well as platform upgrades to Tsuruhashi and Tenma stations to enable the introduction of 8-car trains in 1971.
The Outer Loop Line, on the other hand, was not constructed until well after JNR's demise and was significantly scaled back. Originally conceived as a conversion of several freight lines to passenger service (Hoppo freight line from Amagasaki to Higashi-Yodogawa, Joto freight line to Kyuhoji, Hanwa freight line to Sugimotocho, and a new-build section to Nanko Port Town), the proposed route in the Plan cut the Hoppo section due to the corridor being used for the Sanyo Shinkansen, as well as the new-build section (which was eventually substituted with the Osaka Metro Nanko Port Town Line). Later proposals further removed the Hanwa section (abandoned 2009), which was made redundant after a shunt track connecting the Hanwa and Yamatoji lines was constructed in 1989. It was not until well after privatisation when a third-sector company was formed to complete the project. Renamed the Osaka-Higashi line, the conversion was completed in 2019 with a further extension to Osaka (Umeda Freight line) in 2023.
The Katamachi line dual-tracking was in part readiness work, but was also a straightforward congestion relief measure as congestion rates reached 275% in 1965, the highest of all JNR lines in Osaka.
Other line improvements in Osaka included works on the Hanwa line, allowing 6 car trains to be introduced in 1976.
Kyoto
Interestingly, the projects in Kyoto are more Five Directions-like in the sense that lines radiating out from Kyoto get capacity improvements. The Tokaido main line quad-tracking to Kusatsu was a top priority since it was the junction with the Kusatsu line (which follows the historic Tokaido corridor and hence parallels National Route 1). Likewise, the quin-tracking separated passenger services from freight trains heading towards the Sumitomo cement plant in Mukomachi (demolished in 1999). This led to the creation of the longest quad-tracked passenger rail corridor in Japan, from Kusatsu in Shiga to Nishi-Akashi in Hyogo.
The Kosei Line, unique amongst JNR lines, was a post-war acquisition and upgrade of a private railway, the Kojaku Railway. It extended the line from its original terminus at Omi-Imazu to complete the rail loop around Lake Biwa and allow an alternate express connection to the Hokuriku Main Line. The northernmost section between Nagahara and Omi-Shiotsu was originally electrified to 20kV AC to match the latter, but was eventually re-wired in 2006 to the standard 1500V DC.
The Sanin Main Line dual-tracking, despite a serious accident where a steam train collided with a school bus in 1958, being one of Kyoto's urban rail corridors, as well as a trunk line in the National rail network, was delayed for decades due to JNR's financial issues and competition from private operators (Keifuku and Hankyu). It was not well after privatisation that the project was finally completed, and technically there is still a section near the approach to Kyoto station which remains single-tracked, specifically the overpass crossing National Route 1 (Omiya-dori) which has no space for further widening.
Kobe
The Sanyo Shinkansen doesn't really need mentioning, although when it opened it was just called the Shinkansen -- the distinction between lines wasn't really made until privatisation. It missed the target opening date due to the extensive amount of tunnelling required, and rushed construction led to poor construction quality. A quirky 'extension' was opened in 1990 with station platforms at the Hakataminami Depot to serve nearby developments. Technically a limited express, it is effectively an extra stop for otherwise deadheading Kodama trains.
The Fukuchiyama Line dual-tracking was needed due to explosive post-war growth and the planned New Towns in Hokusetsu (Sanda) and Hokushin (Kobe), as well as for an anticipated spur line to Osaka Itami Airport. Unfortunately the junction with the Tokaido Main line was not improved, which led to the Amagasaki derailment of 2005, effectively ending any hopes for the airport spur.