Built between 1956 and 1963, the Kurobe Dam stands as a monumental engineering feat in the northern Japanese Alps of Toyama Prefecture. Reaching a height of 186 meters, it required over 1. 5 million cubic meters of concrete.
However, transporting heavy machinery, materials, and thousands of workers to such an isolated, avalanche-prone alpine ravine posed an unprecedented logistical nightmare. Traditional surface roads were impossible due to heavy winter snowfalls, extreme steepness, and delicate national park ecosystems. The solution was the Kanden Tunnel, a 5.
4-kilometer subterranean path drilled directly through Mount Tateyama. To prevent toxic exhaust buildup in the unventilated, enclosed mountain tunnel, conventional diesel vehicles could not be used. Engineers opted for electric trolleybuses powered by overhead wires.
The system eliminated emissions while providing high torque needed to haul massive construction loads up steep grades. During construction, workers famously hit a massive fractured zone spewing ice-cold water and rock at 200 liters per second, delaying the project by months. Once the dam was completed, the trolleybus route was preserved as part of the Tateyama Kurobe Alpine Route, serving millions of tourists.
Operating entirely underground, it remained one of Japan's most unique zero-emission transit networks for over five decades before transitioning to battery-electric buses in recent years.