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.
The rock through which the tunnel was drilled was described by a geologist as 'good tunnelling rock'. No tunnel lining was needed and only a few anchors, which were drilled and bolted where required.
The two trains were substantially renewed in 1994.
Trains run on a single track through most of the tunnel, although there is a passing loop at the mid point, where a 638m horizontal escape tunnel is located.