The Amazing Strengths and Weaknesses of Japan’s Shinkansen We Can Be Proud Of ⑥ ~A Battle Against Tunnel Shockwaves!~

Last time, we talked about ‘switches’ (points). This time, as promised, we will be talking about ‘narrowness.’

When we say “narrow,” we are not referring to the size of the Shinkansen cars. As you find out when riding the train yourself, there are five sections in total: two and three columns. On JR East’s Tohoku Shinkansen or Joetsu Shinkansen, there were even models with six sections (three + three). Generally, conventional limited express trains typically have four sections (two + two). It is clear that Shinkansen cars are wide. The “narrow” aspect we discuss today refers to the narrowness of the “tunnels” and the passing loops.

The standard tunnel cross-section for Japanese Shinkansen is about 65㎡. While this size is sufficient for even large Shinkansen bodies, the international standard for high-speed rail is over 100㎡. The reason why a larger tunnel cross-section is better is that the smaller it is, the greater the air resistance when the train enters the tunnel, which increases the impact and shaking experienced by the train. Furthermore, when a vehicle enters at high speed, the air inside the tunnel is pushed to the opposite side, causing a shockwave called “Tunnel Don” at the exit on the other side, sometimes accompanied by a cannon-like sound. The passing loop distance also forces us to describe it as “narrow.” While the standard center-to-center track distance for Japanese Shinkansen is about 4.3m, international high-speed rail lines often exceed 5m. Some sections of France’s TGV high-speed line are even 10m apart. For Japan, which wants to minimize land acquisition and construction costs as much as possible, this must have been a difficult compromise, but it created problems regarding impact and shaking during high-speed passing.

How did they overcome these respective issues? The first 0 series Shinkansen had a face that resembled a round nose. Today’s main vehicle for the Tokaido Shinkansen, the “N700 series,” bears little resemblance to the 0 series except for the white background and blue line. This is because it was designed using a “Genetic Algorithm.” Although I am from a humanities background and couldn’t fully grasp what ‘Genetic Algorithm’ meant… in any case, by incorporating this technology and designing the train with a constant rate of cross-section change when entering tunnels, that face was completed. It became a uniquely Japanese design, different from overseas high-speed rail faces that didn’t have to worry much about tunnel issues. Furthermore, it goes without saying that this design proved effective in reducing impact and shaking during passing.

How was it? Japan’s Shinkansen is incredible, but it also has various weaknesses. They have overcome these through various technologies and countermeasures. The evolution of the Shinkansen continues rapidly. We must keep our eyes on its future development.

Well, see you next time!