In short: Rt.140, a vital link between Saitama and Yamanashi isn’t yet open to bikes due to a rock fall. And what is the West Kanto Connecting Road?

If you’ve tried to ride Rt.140 from Saitama to Yamanashi since July 11, you’ll know that you can’t get through. You can get around 50km in from Yamanashi and 20km in from Chichibu. You may have also noticed that there’s a tunnel there open to cars, trucks and moped-class motorbikes that is far from finished. So what’s going on there? A fair bit more than just tunnel bypass…

The unexpected, provisional opening of the Otaki Tunnel on National Route 140 in Saitama Prefecture on July 30 is more than just a temporary fix for an often disaster stricken road. Although still an unsealed gravel road and thus not yet open to motorbikes, bicycles or pedestrians and not announced when it will be, it is the first step in a much larger, ambitious project.

While the rockfall brought forward the tunnel’s opening, the Otaki tunnel’s mere presence highlights the long-term vision of a vital artery for the region—and a new chapter for one of Kanto’s more scenic mountain roads and an awesome ride from Chichibu to Yamanashi either side of Japan’s 5th longest road tunnel, Karisaka Tunnel. But are more tunnels like these good for us riders?

For years, the section of Route 140 that meanders along the Arakawa River west of Chichibu has been a test of stamina, nerve and skill. With its sharp curves clinging to and carving through the steep mountainside, the road is picturesque but perilous, a frequent victim of rock falls, occasional landslides and accidents. The slow addition of newer smoother sections is helping but every rockfall, landslide or washout leaves locals and travelers with no detour, thus the need for more reliable options.

Previously scheduled to open in 2027, the Otaki Tunnel though currently unpaved, with a restrictive 15 km/h speed limit and not open to larger bikes, provides that reliability. For now, it’s an incomplete solution—an unsealed dusty, cone-lined dark channel there simply to get traffic through again. For those who rely on Route 140 as a critical link between Chichibu and Yamanashi, this tunnel will mean a reduction in travel time and another step towards safe reliable access.

However, every new ‘efficient’ road has a trade-off. The tunnel’s efficiency will come at the cost of bypassing a scenic and twisting section of the old road, a loss for riding and driving enthusiasts who relish the challenge of a fun mountain drive. With its river views and dramatic mountain backdrop, it offers a unique experience that a straight tunnel just can’t replicate. Thankfully, the currently closed section has residents and businesses lining it, so will likely be reopened and remain a fun longer way there. Fingers crossed…

The Otaki Tunnel is not an isolated project, but rather a key component of a massive undertaking: the West Kanto Connecting Road. This high-standard road system, envisioned to follow Route 140 from the Kanetsu Expressway to Yamanashi and the Chuo Expressway, is slowly but surely being pieced together. Sections like the Minano Yorii Bypass and Minano Chichibu Bypass are already in place, and the Ganzaka Tunnel Toll Road further demonstrates the commitment to this grand plan. Once complete, the West Kanto Connecting Road is planned to contribute to a crucial loop with other expressways, dramatically improving connectivity and creating a high-standard road network outside the Ken-O Expressway.

Can’t help as a rider wondering how attractive this new free short cut will be to bumbling trucks and tour buses though. Less twisties and more moving road blocks isn’t ideal but that area is still loaded with twisties off the beaten track, I guess.

The provisional opening of the Otaki Tunnel may be a small, dusty step, but it is a poignant one. It marks another step in a transformation of mountain roads diluting rider enjoyment, by turning a structurally difficult and dangerous mountain route into a dependable, modern artery. It’s an inevitable addition to a complex puzzle, signaling that the vision for the West Kanto Connecting Road is moving from concept to reality, one tunnel and one bypass at a time.

The countryside locals reliant on Rt.140 have waited a long time for the Otaki Tunnel, and similar vital links like it will hopefully bring much-needed ease of access to countryside communities. This in turn may hopefully aid in some small way to reverse the long-term exodus of residents, thus ensuring the continued maintenance of the honeypots of remote mountain twisties we riders cherish. 🤞

For now, with reduced traffic, the hillclimb, tunnel and twisties from Yamanashi to Otaki Tunnel and back sounds like a great 100km run. 😉

Sources:

Saitama Prefecture Website https://share.google/ctygjWHsyXhHnlMkB

Chishima Surveying and Design Co., Ltd. https://share.google/q0Kz7uMBhyVG4G1U7

+ Various news outlets.