Shinkansen trains, from the first-generation 0 Series to the latest E8 Series, all feature a streamlined design for the front part of the train. In particular, recent models like the N700S and E5 Series are characterized by their complex and elongated front shapes.
One reason for the streamlined front design is to minimize air resistance. The first-generation 0 Series operates at speeds of up to 210 km/h, while the current fastest trains, the E5 Series and E6 Series, reach speeds of 320 km/h. Boxy train designs would result in higher air resistance. Therefore, a streamlined shape is used to smooth the airflow and reduce unnecessary drag.
Another important reason is to reduce compression waves. When a Shinkansen enters a tunnel at high speed, the air inside the tunnel gets compressed, creating a pressure wave that propagates at the speed of sound towards the tunnel's exit. This phenomenon, known as "tunnel boom," generates a loud noise at the tunnel exit and can affect nearby buildings. Various measures have been taken to address this issue.
One such measure is the adoption of long and complex front shapes on recent Shinkansen models. Instead of a simple streamlined shape, the design of the front part has been refined to mitigate tunnel boom.
In contrast, high-speed trains in Europe, such as France's TGV, Germany's ICE, and Italy's Frecciarossa, have shorter and simpler front shapes compared to Japan's Shinkansen. European high-speed trains do not face the same severe tunnel dimensions and noise regulations, so tunnel boom is less of a concern.
Recent Shinkansen models, such as the E7 and W7 Series operating on the Hokuriku and Joetsu Shinkansen lines, have simpler front shapes compared to the E5 Series on the Tohoku Shinkansen. The E7 and W7 Series, which operate at a maximum speed of 275 km/h, do not require as extensive tunnel boom measures as the E5 Series.
On the other hand, the ALFA-X, a test train developed with the goal of achieving a maximum speed of 360 km/h, features a more bold front design than the E5 Series. Since ALFA-X is a test vehicle, the exact shape of future commercial trains remains uncertain. However, if speeds exceeding those of the E5 Series are achieved, it is likely that even more complex front designs will be introduced.
