Data sources

How the passes in this guide were chosen, and the sources of the locations, elevations, road data, 3D views and weather.

Passes included

The 31 passes on Hokkaido's national routes listed in these two sources (in Japanese):

MLIT list of preventive closure sections (FY2025, Hokkaido): sections the national government closes in advance when exceptionally heavy snow is forecast. The Jukai Road section (Route 274) is not a pass and is left out. There are two Tenpoku Passes, on Route 239 and Route 275.
Kita-no-Michi Navi mountain pass information (Civil Engineering Research Institute for Cold Region): 25 passes. It treats Shizukari and Rebunge passes as one section, and so does this guide (on the Shizukari Pass page).

Pass locations

23 passes: we found the pass name in the Place labels in GSI vector tiles and placed the pass at the nearest point on the road. Road lines are from OpenStreetMap.
7 passes: with no name on GSI Maps, the pass is the highest point of the road (excluding tunnels and bridges) between the two ends of the preventive closure section.
1 pass: with no name on GSI Maps but known to lie on a municipal boundary, the pass is where the road crosses that boundary, found with the GSI reverse geocoder.

Elevations

25 passes: from Kita-no-Michi Navi mountain pass information (Civil Engineering Research Institute for Cold Region), which is based on a 2001 road handbook.
6 passes not in Kita-no-Michi Navi: the highest point of the road near the pass (excluding tunnels and bridges) in GSI elevation tiles (10 m mesh), marked "about".

Where a road crosses a pass in a tunnel, the ground above is higher than the road. For passes without tunnels, Kita-no-Michi Navi's values matched the road height from GSI elevation data to within a few meters.

Road data

Section length, steepest grade, minimum curve radius, road width and chain-up areas are from Kita-no-Michi Navi mountain pass information (Civil Engineering Research Institute for Cold Region). Preventive closure section lengths are from the MLIT list of preventive closure sections (FY2025, Hokkaido).

Location and area

We looked up the municipality of the pass, and of eight points 300 m around it, with the GSI reverse geocoder. Passes often sit on municipal boundaries, so several municipalities may be listed. Areas follow the pass's municipality, using the same six areas as our roadside station catalog.

3D view

The 3D view on each page is built in your browser from GSI Tiles (elevation tiles and the latest seamless aerial photos). The orange road line is OpenStreetMap data drawn onto the aerial photo by this site. The thumbnails in the lists are captures of this 3D view.

Weather

The rain radar and rain forecast are images from the Japan Meteorological Agency's High-resolution Precipitation Nowcasts and Very-short-range Forecasting of Precipitation, shown on the map as they are. Forecasts are by the Japan Meteorological Agency, not by this site. Sunrise and sunset times are calculated from the pass's latitude and longitude.

Maps

The maps use GSI Tiles (pale map) and OpenStreetMap.