Sapporo to Rumoi, the phantom highway

For twenty-eight years this road was a national highway that did not go anywhere. Route 231 was designated in 1953, and for most of the distance between Sapporo and Rumoi it simply did not exist: the Shokanbetsu mountains come down into the Japan Sea in cliffs a hundred metres high, and the road stopped at both ends of them. The administrator’s own name for it was maboroshi no kokudō — the phantom national highway. It was finally joined up on 10 November 1981, and forty days later it fell in.

§ 01

One kilometre in five is under concrete

Start with what the road is physically made of, because it explains everything else. Counted along the Route 231 centreline and measured from their own geometry, there are 21 tunnels totalling 21.91 km and 12 snow sheds totalling 2.20 km in the 126.7 km from the edge of Sapporo to Rumoi. That is 24.11 km of road with a roof on it — 19.0 per cent of the whole corridor. Nothing else on this site comes close. The Shiretoko crossing, which is a mountain road over a volcano, is bare by comparison.

The longest of them are not short. The Hamamasu Tunnel runs 4,018 m, the Shin-Okurige 3,012 m, the Higatatomari 2,919 m and the Futoshimanai 2,446 m. Those four alone account for more than twelve kilometres. If you drive this road and feel that you have spent a surprising amount of it looking at tunnel lighting rather than at the sea, the feeling is correct and now has a number attached to it.

§ 02

It is really two roads

The 19 per cent is an average across two completely different roads, and the average flatters the first one and libels the second. From Sapporo out through Ishikari and Atsuta — the first 46 km — there is one structure, a 244 m snow shed, and the road is 0.5 per cent covered. It is an open coastal run with the sea on your left and nothing much in the way.

Then from about kilometre 46 to kilometre 102 — the 56 km through Hamamasu, past Ofuyu and on to Mashike — there are 32 structures and the road is 40.3 per cent covered. Two kilometres in every five are inside something. Around Ofuyu it becomes almost comic: thirteen separate tunnels and sheds inside five kilometres, some of them under a hundred metres long, strung end to end along a cliff face. After Mashike it relaxes again — 5.2 per cent over the last 24.7 km into Rumoi. The sheet is one corridor, but the middle third of it is a different kind of engineering from either end.

§ 03

The village that was an island

Ofuyu sits on the boundary between what was Hamamasu village and Mashike town, in the middle of that cliff section, and until 1981 no road reached it from either side. The administrator’s account is plain about what that meant: Ofuyu had one scheduled boat a day, from Mashike, and that was the only way in or out. When the sea got up and the boat did not run, the place was cut off completely — riku no kotō, the land-locked island.

It is worth sitting with the geometry of that for a moment. Sapporo is about ninety kilometres away. There was no boat to Sapporo. To reach the largest city in Hokkaido from a village on the Hokkaido mainland, you took the daily boat north to Mashike and then a bus back south. That was ordinary life there within living memory, and it ended on a specific afternoon in November 1981.

Mashike’s own town chronology supplies two details that put the isolation in sharper focus than any description could. Ofuyu and neighbouring Iwaoi were the last districts in Hokkaido to get automatic telephone exchange, in 1978 — three years before the road arrived. And the scheduled boat between Mashike and Ofuyu did not stop when the road opened in 1981. It kept running for another eleven years, and closed in 1992, the same year the new route around Obetsukari opened. People went on taking the ferry until the road was not just connected but reliable.

§ 04

Built from the sea

The hard part was the stretch between Ayumikotan and Ofuyu, where the cliffs are continuous and there was no land route to bring anything in on. The solution, from 1962, was to stop trying: the bureau established four landing bases on the coast — at Ayumikotan, Higatatomari, Yudomari and Akaiwa — and shipped the construction machinery and materials in by sea, building outward from each beachhead. That section, which is the tunnel chain you now drive through in a few minutes, took nineteen years and opened in November 1980.

The Rumoi end had started even earlier, in 1958, with twelve kilometres from Obetsukari to Ayumikotan that were not passable until 1973. When the Sapporo side finally met it on 10 November 1981 there were two opening ceremonies, and then a joint one at the Shirogane bridge at Ofuyu, where the mayor of Mashike and the head of Hamamasu village shook hands. The administrator’s record of this is not written in the tone of a civil engineering document, and I do not think it is trying to be.

§ 05

Forty days

Then, in the bureau’s own word, the opening was overtaken by a nightmare. Forty days after the road was joined up, the Ofuyu-misaki Tunnel on the Sapporo side collapsed. The road closed again, and this time the repair took two years: the work was finished in December 1983, but it was winter and the road stayed shut, so Ofuyu did not actually get its connection back until 15 May 1984.

Nineteen years of construction, a handshake on a bridge, and forty days of road. That is the part of this corridor I find hardest to drive past casually. The defences have been rebuilt repeatedly since — a new route around Obetsukari with its own tunnel in October 1992, disaster-prevention works at Mashike from 1993, and the Higatatomari Tunnel driven later as what the bureau calls a fundamental countermeasure — and the reason given each time is the same one: the cliffs here are over a hundred metres high and there is no alternative road.

§ 06

What actually closes this road

This is the practical heart of the sheet, and it is a genuinely unusual answer. Two stretches of Route 231 through Hamamasu — Horo to Chiyoshibetsu, and Chiyoshibetsu to Ofuyu — are listed by the road administrator as special traffic-regulation sections. Most regulated sections in Hokkaido have a number attached: the Shakotan coast on Sheet 02 closes when continuous rainfall reaches 100 mm, measured at a named telemetered station. You can watch that number approach.

These two sections have no station and no threshold. The published closure condition is, in full: when a patrol judges there is a risk of rockfall or avalanche. That is the whole criterion. There is no rainfall figure you can check against a forecast, because the hazard here is not really rain — it is a hundred-metre rock face, and whether it is about to let go is a judgement someone makes by driving along underneath it and looking.

I would rather have the patrol than the number, given what happened in 1981. But it does mean you cannot plan around this road the way you can plan around Shakotan. There is nothing to monitor; you check the live restrictions, or you arrive and find out.

§ 07

One number, for once

Most sheets on this site carry two distances — the fastest way and the way worth driving — and they usually disagree sharply. The Nissho sheet is 217 km against a 181 km fastest route that never goes near the pass. Here they agree: the fastest route from Sapporo to Rumoi is 131 km and about an hour and a half, and it is this road. At the midpoint of the coastal section the two lines are 0.0 km apart.

There is no inland alternative because there is no inland. That is the same fact as the cliffs, the same fact as the tunnels, the same fact as the patrol, and the same fact as the nineteen years. The reason this road is interesting is that there was never anywhere else to put it.

§ 08

The bird the road is named after

The coastal route is called the Ororon Line, and the name is not a place. It is a bird: the common guillemot, known here as the ororon bird for its call. It is the reason the corridor on this site is labelled the way it is, and it is worth knowing what the name now refers to.

The common guillemot is listed by the Ministry of the Environment as critically endangered, and it breeds at exactly one place in Japan: Teuri Island. It used to breed on three others. The counts at Teuri run about 8,000 birds in the 1960s, 500 to 1,000 in the 1970s, 130 to 600 in the 1980s, 20 to 80 in the 1990s, and around 30 after 2000. To draw the birds back the ministry puts decoys on the cliff and plays a recording of the call through a loudspeaker, and controls the crows and gulls that take the eggs.

It has worked, slowly. The count passed fifty in 2017, and in 2025 it reached 135 birds, 37 pairs and 24 fledglings — the highest since the collapse. So the road is named for a call that had to be put on tape and played back at the cliff to summon what was left of the thing that made it. Be straight about the geography, though: Teuri lies off Haboro, well north of Rumoi, so it is not on this sheet. You finish this corridor and the island is still ahead of you.

§ 09

The railway that is no longer an answer

There used to be a second way up this coast. The railway reached Mashike from Rumoi in 1921, and for most of the twentieth century the Rumoi Main Line was the alternative to a road that did not yet exist. It has been dismantled in three stages. The Mashike end went first, in 2016. The Ishikari-Numata to Rumoi section ran its last train on 31 March 2023. The final stub from Fukagawa ran its last train on 31 March 2026 and the railway business formally ended the next day — a line that had opened in November 1910, closed six months before this sheet was written.

I mention it because it changes what “no alternative” means. When the Ofuyu tunnel collapsed in 1981 there was still a train to Mashike. There is not now. The buses that replaced the railway use the road, which means that on the days a patrol closes the cliff section, the road and its replacement service fail together. That is a thinner margin than this coast has had at any point in the last hundred years, and it is the strongest practical argument for checking the restrictions before you commit to the drive.

§ 10

Where this sheet joins the others

This is the ninth and last of the corridors mapped on this site, and it is the northern one. It leaves from the same city as the Hakodate sheet, which goes the other way entirely, and it is the natural pair to the Shakotan coast: two cliff roads on the same sea, regulated by opposite philosophies. Rumoi is also where the Ororon Line stops being this road and becomes Route 232, heading north for Haboro, Teuri and eventually Wakkanai.

§ 11

The car, and when to go

This is the easiest driving of any sheet here — no pass, no sustained climb, no gradient worth quoting — and the difficulty is entirely in the weather and the rock. Go between late spring and October if you can. The road is kept open through the winter, but a cliff road with twelve snow sheds on it is telling you what the winter is like, and the section that closes on a patrolman’s judgement is exactly the section you cannot skip.

Fill up before the cliffs rather than in them, and do not plan a tight connection at the Rumoi end. The honest way to drive this corridor is to treat the first 46 km as transit and the middle 56 as the sheet: come out of the Hamamasu Tunnel, pull over at the first place that lets you, and look back at what nineteen years and four beachheads bought. For what the roads are like in general, the general guide covers surfaces, winter tyres and the rest, and the distance table has Rumoi in it, measured like everything else.