The tunnel was originally built to efficiently bring supplies to the site for the construction of the hydroelectric plant of Kurobe Dam, by the Kansai Electric Power Company (Kanden or KEPCO).

It is only one lane wide, except for a short section near the middle, which is wider so as to allow vehicles going in opposite directions to pass.

[clarification needed] During peak hours, multiple buses operate through the tunnel in convoys.

[1] The original fleet comprised six Mitsubishi Fuso trolleybuses with bodies by Osaka Sharyo Kogyo, built in 1964, numbered 101–106 (renumbered 111–116 in 1976).

Additional vehicles built by the same manufacturers, to the same or very similar design, were acquired gradually—at a rate of about one new trolleybus per year—between 1966 and 1973, carrying fleet numbers 107–110 and 201–205 (renumbered 117–120 and 211–215 in 1976).

All of the 1964–1973 vehicles were withdrawn from service in the early to mid-1990s and replaced by a new fleet of nine trolleybuses built by the same two manufacturers,[8] in 1993 and 1994, and numbered 301–309.