Replacement with 2-Car Diesel Railcars for Type 70-000 and 303 Series on the Non-Electrified Chikuzen-Maebaru ~ Nishi-Karatsu Section? - JR Kyushu Chikuhi Line Timetable Revision Prediction (Scheduled for 2040 or Later)
Table of Contents
- Replacement with Diesel Railcars on the Little-Used Chikuzen-Maebaru ~ Nishi-Karatsu Section of the Chikuhi Line?
- Will the Discontinuation of EMU Access to Karatsu Depot Lead to Diesel Replacement for Retired 70-000 Series and 303 Series?
- When Will the Chikuhi Line's 70-000 Series and 303 Series Be Replaced?
- Conclusion
Replacement with Diesel Railcars on the Little-Used Chikuzen-Maebaru ~ Nishi-Karatsu Section of the Chikuhi Line?
JR Kyushu is currently operating one of the 3-car 103 series trainsets used on the Chikuhi Line in the revival livery from its initial service period.
A revival livery for railway rolling stock often indicates its impending retirement. Indeed, the 103 series used on the Chikuhi Line began service in 1983 and is already over 42 years old. Six out of the initial nine 6-car sets were replaced by new 305 series 6-car sets (six trainsets) between February and March 2015. The remaining Chikuhi Line 103 series trains were modified into five 3-car sets, but no new replacement rolling stock has been announced yet.
The average transport density for the Chikuzen-Maebaru ~ Karatsu section, where the 3-car 103 series operates, was 5,061 passengers/day (both directions) in FY2023. Assuming one train per hour during daytime can carry 4,000 passengers/day (both directions), two trains per hour during daytime would be sufficient, even allowing for some fluctuation. Although fluctuations are possible, there are no intermediate stations on the Chikuzen-Maebaru ~ Karatsu section with an average daily boarding exceeding 1,000 passengers, and only Chikuzen-Fukae exceeds 500, suggesting no adjacent station section has a transport density over 8,000 passengers/day (both directions) that would necessitate more than two trains per hour.
With this volume, 3-4 trains per hour during weekday evenings and 5-6 trains per hour on weekday mornings would suffice. Considering the Chikuhi Line operates 4 trains per hour on the Chikuzen-Fukae ~ Karatsu section on weekday mornings, 2-car formations would be adequate for all-day operation. Thus, reducing the current 3-car 103 series EMUs to 2-car formations would be entirely feasible. Consequently, it is anticipated that from the March 2026 JR Kyushu timetable revision, they will be replaced and downsized by five 2-car 70-000 series EMUs transferred from the Tokyo Waterfront Railway Rinkai Line.
Although the transport density might not seem to justify removing electrification infrastructure, the Chikuhi Line was initially a single-track, non-electrified line. It was reorganized alongside DC electrification to enable through-services to Tenjin via the Fukuoka City Subway, and to integrate major stations within Karatsu City by constructing piers at the mouth of the Matsuura River. This allowed through-services to Karatsu Station starting in 1983, coinciding with the through-service to the Fukuoka Municipal Subway and electrification, and the Karatsu Rolling Stock Center was established near Nishi-Karatsu Station for inspecting Chikuhi Line EMUs.
However, because the Chikuhi Line EMUs use DC to match the subway, they are incompatible with most of JR Kyushu's AC EMUs, requiring separate facilities. Only nine 6-car 103 series sets were initially introduced, and even after adding three 6-car 303 series sets later, the total remains only twelve sets. Therefore, JR Kyushu does not maintain its own major inspection facilities for them, relying instead on the Fukuoka City Transportation Bureau's Meinohama Depot.
Under the current operational schedule, JR Kyushu's trains essentially run as "empty carriage services" with 6-car formations on the Chikuzen-Maebaru ~ Nishi-Karatsu section. This persists despite the March 13, 2021, timetable revision, which made most Chikuhi Line services require a transfer at Chikuzen-Maebaru and downsized many from 6-car to 3-car 103 series formations.
Therefore, if all inspections were consolidated at the Meinohama Depot, eliminating the need for EMUs to enter/exit Karatsu Rolling Stock Center, could the Chikuzen-Maebaru ~ Nishi-Karatsu section be de-electrified to reduce costs?
Will the Discontinuation of EMU Access to Karatsu Depot Lead to Diesel Replacement for Retired 70-000 Series and 303 Series?
Furthermore, de-electrifying the Chikuzen-Maebaru ~ Nishi-Karatsu section would also allow for a reduction in operations for the 6-car sets used for through-services to the Subway Airport Line.
Currently, operations involving fixed 6-car formations of the 303 and 305 series are frequent, primarily during morning/evening peaks for depot access at Karatsu. However, if through-services of fixed 6-car sets to Karatsu were eliminated, their operation would be limited to round trips between Fukuoka Airport ~ Chikuzen-Maebaru, or at most to Chikuzen-Fukae. This could potentially reduce Chikuhi Line 6-car EMU operations by three diagrams. Consequently, there would be no need to replace the three fixed 6-car 303 series sets (introduced in 1999, now over 23 years old) with new EMUs.
In that case, wouldn't both the 70-000 series and the 303 series become candidates for replacement by diesel railcars if the section is de-electrified?
When Will the Chikuhi Line's 70-000 Series and 303 Series Be Replaced?
So, when will the 70-000 series and the 303 series be replaced?
If the replacement is part of de-electrification, the nine required 2-car diesel railcars would likely be introduced simultaneously. Therefore, the 70-000 and 303 series are best viewed as being replaced concurrently.
Perhaps the temporary replacement of the 1983-built 103 series with second-hand 70-000 series EMUs was a strategy to align their replacement schedule with the newer 303 series, facilitating a simultaneous future switch to diesel railcars.
Given that railway rolling stock lifespan is typically 40-50 years, aiming for de-electrification around 2040-2045 and replacing both the 6-car 303 series and the 2-car 70-000 series with 2-car diesel railcars seems plausible.
Thus, a possible scenario is: around March 2026, replace the five 3-car 103 series sets with five second-hand 2-car 70-000 series sets as an initial renewal. Then, around 2040, when planning de-electrification, replace the five 2-car 70-000 series sets and the three 6-car 303 series sets with eight 2-car diesel railcar sets.
Conclusion
This prediction for the JR Kyushu Chikuhi Line timetable revision beyond 2040 anticipates that, to reduce maintenance costs, the Chikuzen-Maebaru ~ Nishi-Karatsu section will be de-electrified, 2-car diesel railcars will be introduced, and the aging 303 series and 70-000 series EMUs will be replaced.
We will watch with interest what future timetable revisions JR Kyushu implements for the Chikuhi Line.
