An east-bound 300 series bullet train entering Nihonzaka Tunnel. The tunnel shows no evidence that this is in fact an old bullet train tunnel dug before World War II.

By Hiroshi Naito

'The real bullet train' by Dr Christopher P. Hood in Bullet-in #43 really recalled one of my old memories. The memory dates back to the late 50s through the early 60s when I was a child. As Dr Hood wrote, before the War, due to the establishment of the bullet train plan, about around 20 % of the land required for the planned route was acquired, and work to construct two tunnels even began. One of them is the famous, long New-Tanna tunnel, which was partially dug, and the other was a tunnel, named Nihonzaka Tunnel, located between Mochimune and Yaizu on the Tokaido Main Line in Shizuoka prefecture, which was thoroughly completed. When you travel down on a Shinkansen train, after leaving Shizuoka, crossing a fairly long bridge over the Abe River, a mountain range comes closer to you from the northwest. Soon, your train runs into a thick flank of the mountain that reaches down as far as the sea blocking your way, but your train goes straight through a tunnel penetrating the flank. This is the oldest tunnel over the entire Shinkansen route that was dug before and during the War. Actually, I used to go through this tunnel many times when I was a child more than 40 years ago, on an electric loco-hauled train, without any knowledge of the old bullet train. Yes, the tunnel was put in use for the Tokaido Main Line after the War, changing the route from the old tunnel that took a coastal route that is only just over one hounded meters away.

In my boyhood days, I was living in Shizuoka city. Since my parents both were from the western part of the prefecture, we had many relatives around the Hamamatsu area. Visiting the relatives during school holidays to Hamamatsu and as far as Bentenjima (Benten Island on Hamana Lake) was a great pleasure for me, because I was able to ride a train over a long distance. It was only an about a 90 km trip with a ride of about 2 and half hours, but enjoyable enough for a kid raised in that poor era just after the War.

Through the trips, I knew that there were two long tunnels on the segment between Shizuoka and Hamamatsu. One was that bullet train tunnel, and the other was a tunnel west of Kanaya on the west bank of the great Oi River. The kid got aware that there was a big difference between these two tunnels. The western tunnel, which started just from the western edge of the platforms of Kanaya station, consisted of two single-track bores with rather small cross sections. I felt a little claustrophobia with small clearances to the brick-made side walls when I went through the tunnel in a coach behind an electric locomotive. In contrast, the Nihonzaka tunnel was a single bore accommodating double-track, and I could recognize the modern tunnel technology with its concrete-built side walls retaining enough clearances outside my coach.

In addition, I have two episodes to tell concerning the Nihonzaka tunnel.

Phantom Railway:
An unforgettable sight showed up whenever I left the Nihonzaka tunnel on my west-bound trip. To the west of the tunnel was open space of rice fields all around the recessed mountain edge. I saw an embankment diverging off the main track just after the end of the tunnel. The embankment, which apparently was built of the dumped soil form the tunnel, appeared to be a railway track when seen from a certain distance. It continued over some hundreds meters gradually separating from our track towards the west. I always wondered at this unused embankment without any idea about the old bullet train plan: what this was for, a new railway, but if so, why? Of course, I could not find out any reason why that railway track-like embankment extended through the sparsely populated rural district. It looked as if to bring a heavy high-speed train running towards us. It was memorized as a phantom railway into the mind of an innocent kid.

Sekibe Tunnel:
The old coastal tunnel used to comprise two sections, Sekibe tunnel and Isohama tunnel, each about 1.3 km in length, which were completed in 1889 prior to the full opening of the Tokaido Main Line. The area was a geographically difficult spot being blocked by a fairly precipitous mountain flank that reached down directly to the sea forming a rigid sea coast with sharply rising hillsides. Actually, this sea coast was known as Okuzure Kaigan (Great Collapsed Beach), and was one of the destinations of a school excursion around Shizuoka city. The old Tokaido road and modern national road #1 took a detour route across the Utsunoya Pass avoiding this tough path. The prefectural road connecting Shizuoka city and Yaizu city took a coastal route clinging to the sheer hillside, but traffic blockage often occurred due to landslides caused by heavy rain or typhoons. The railway tunnels, consisting of two single-track bores, were also dug just along the edge of the mountain flank. Between the two tunnel sections was a short open path sticking to a cliff facing the sea of Suruga Bay.

One day, probably when I was a junior-high school student, I visited the abandoned Sikibe tunnel by bicycle with some of my friends. We ventured to travel through the tunnel on our bikes. Inside the tunnel was a rugged dirt road with many water pools here and there. In darkness, the only light that helped our progression was the dim headlight of my bike. The soot stained side wall was telling that the steam era was not a long time ago. After close to one hour struggling in darkness, we finally reached the other end and emerged onto a short intermediate terrain sandwiched between the sharp precipice and the wild beach. What struck me there was part of the tunnel portal had collapsed on the beach in some blocks.

Soon, as the Shinkansen route was disclosed by the mass media, I came to know that the Nihonzaka tunnel, in fact, was dug for the construction of the old bullet train. It was exciting to know that the Shinkansen was going to use that double-track tunnel and the Tokaido Main Line was resuming that old coastal route. I felt happy that the phantom railway seen to the west of the Nihonzaka tunnel was coming true.

When I first traveled west on a bullet train after opening of the Shinkansen, I was curious about how the area had changed after leaving Shizuoka and crossing over the Abe River. However, the train passed through the Nihonzaka tunnel in a moment without showing any evidence of the old bullet train tunnel. After finishing the tunnel, the train zipped through the open space of rustic scenery along the embankment which I once dreamed of as a phantom railway. Also I tried to travel from Shizuoka to Yaizu by a local train to check the change in that old coastal route. I expected to see the sea at the intermediate section between the Sekibe and Isohama tunnels, but disappointedly I did not see any lights en route. I realized that the tunnels were combined together, guessing that the intermediate section must have been covered by a shelter protecting the railway from that wild geographical environment.

It was quite recently that I got to know of the real background of these tunnels. The Sekibe and Isohama tunnels were bottlenecks for freight traffic on the Tokaido Main Line because of their insufficient clearance, sometimes causing heavy freight to detour to the Chuo Line. Due to increasing demands of freight transportation nearing the War, upgrading the tunnels was raised as an urgent issue. Under this circumstance, as the construction of the bullet train system set out, the Nihonzaka tunnel was dug in advance, intending to detour for the Tokaido Main Line in order to allow a temporary period during which the Sekibe and Isohama tunnels could be upgraded. Thus, the Nihonzaka tunnel was completed in 1944, but the bullet train plan was called off due to defeat in the War. After the War in 1946, the Tokaido Main Line was rerouted to the completed Nihonzaka tunnel, but the upgrade of the old coastal tunnels did not take place until the construction of the Shinkansen commenced fourteen years later. In fact, due to upgrading reconstruction, the coastal tunnels were converted to a single tunnel with re-dug inner bores that bypassed the intermediate open section. The western portal of the Sekibe tunnel was destroyed by a typhoon in 1948.

I heard that the collapsed portal of the Sekibe tunnel is still lying on the beach forming a bleak sight around the area. When you travel down by a local train on the Tokaido Main Line going through Mochimune, if you carefully pay attention out of the window to the right facing Yaizu, you may be able to identify the traces of the old track bed connecting to the Nihonzaka tunnel.

Emerging from the eastern entrance of the old Sekibe Tunnel is an up bound local on the Tokaido Main Line	The precipitous mountain flank reaches down directly to the sea forming a rigid sea coast of the "Great Collapsed Beach (Okuzure Kaigan)".	The prefectural road connecting Shizuoka city and Yaizu city was re-routed with an over-the-sea bridge, seen on the right, abandoning the road tunnel clinging to the sheer hillside, seen on the left.
A bleak sight around the western exit of the old Sekibe Tunnel. The collapsed tunnel portal is seen lying on the beach.	A close up of the destroyed western exit of the old Sekibe Tunnel. The brick-made side walls are clearly visible.	The western entrance of the old Isohama Tunnel still retains an ambience of an old railway tunnel completed more than one hundred year ago.
A 100 series bullet train zips through the open space of rustic scenery along the embankment which I once dreamed of as a phantom railway.	The road diverging to the left is apparently the trail that once connected the Tokaido Main Line track to Nihonzaka Tunnel.	A view of Mochimune across the Shinkansen track with the sea of Suruga Bay in the distance, just east of Nihonzaka Tunnel.