A Straight Bore Across a Town Line
The Kominato Railway Itaya Tunnel (小湊鉄道板谷隧道, Itaya Zuidō) is a concrete railway tunnel of around 1928 running from the Asanohara district of Ichihara City into Itaya in Otaki Town, Chiba Prefecture, and was registered as a Registered Tangible Cultural Property on May 2, 2017. It is the listing closest to the end of the line, and its registration number, 12-0214, is the last of the railway's twenty-two.
The Kominato Railway Itaya Tunnel lies about 1.5 kilometers east of Yorokeikoku Station and straddles two municipalities.
141 Meters with a Refuge
The Agency for Cultural Affairs records it as a straight concrete tunnel 141 meters long and 3.8 meters wide, with a refuge recess inside where track workers could step clear of trains.
The arch and the west portal are built of concrete blocks. The portal face leans back at a batter of 3.5 bu, that is 0.35 horizontally for every 1 vertically, and is scored with grooves to carry off water. The agency singles out this portal treatment as distinctive.
Seeing It
The Kominato Railway Itaya Tunnel is on a working line and cannot be entered. In normal times you pass straight through it by train. If you look at the block-built west portal and its drainage grooves, stay off the track and private land.
Since Typhoon No. 25 struck in September 2026, the line between Kazusa Ushiku and Kazusa-Nakano has been suspended until further notice, with no replacement buses (company statement of September 24, 2026), so for now it cannot be reached by train.
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Q&A
- When was the Kominato Railway Itaya Tunnel built?
- Around 1928, according to the Agency for Cultural Affairs.
- How long is the Itaya Tunnel?
- 141 meters long and 3.8 meters wide, and straight.
- What is distinctive about the Kominato Railway Itaya Tunnel portal?
- The west portal is block-built, battered back at 3.5 bu and scored with drainage grooves.
- Where is the Itaya Tunnel?
- About 1.5 kilometers east of Yorokeikoku Station, crossing from Ichihara City into Otaki Town.
- Can I travel through the tunnel now?
- Not at present. The line beyond Kazusa Ushiku has been suspended since typhoon damage in September 2026.
Basic Information
| Name | Kominato Railway Itaya Tunnel (小湊鉄道板谷隧道) |
|---|---|
| Location | 401-15 Kotanizawa, Asanohara, Ichihara City to 686-3 Heishirobata, Itaya, Otaki Town, Isumi District, Chiba Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2017/5/2 (Heisei 29) |
| Quantity | 1 structure |
| Dimensions | Concrete, 141 meters long, 3.8 meters wide |
| Owner | Kominato Railway Co., Ltd. |
| Public Access | Working line; no access (section suspended after 2026 typhoon damage) |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: 小湊鉄道板谷隧道
- https://kunishitei.bunka.go.jp/heritage/detail/101/00011479
- Cultural Heritage Online: 小湊鉄道板谷隧道
- https://online.bunka.go.jp/heritages/detail/256065
- Kominato Railway: 22 facilities registered as Registered Tangible Cultural Properties (Japanese)
- https://www.kominato.co.jp/corporate/topics/heritage/index.html
- Kominato Railway: Damage from Typhoon No. 25 and recovery outlook, September 24, 2026 (Japanese)
- https://www.kominato.co.jp/wp-content/uploads/2026/09/30216b45daba750194c363de3f54800f.pdf
Last verified: 2026.10.01
