Kaprun's funicular railway was built to speed access to the Kitzsteinhorn ski resort and was one of the first of its kind to be built to serve a ski resort.
Construction of the 3.29km long, 3.6m diameter tunnel started in November 1971, with a tunnel boring machine starting work in August 1972.
It opened in March 1974.
The 38t trains travel at up to 36km/h through the average 42.8% inclined tunnel.
Tunnel and trains are owned by the Geltscherbahnen Kaprun company, a partly private, partly government run company which has responsibility for safety.
Commercial director Peter Braueur admitted that there was no fire fighting equipment in the tunnel.
Developers of other railways, notably at Val d'Isere in France, drew on the Kaprun project when developing designs for subsequent funiculars.