Swiss engineering and technology have reached new heights with the opening of the world's steepest funicular rail line.

The €44.6 million (S$71 million) Schwyz-Stoos funicular, which was opened to the public yesterday, has been hailed as a triumph of modern design engineering.

A level-adjusting function will allow the barrel-shaped carriages to remain horizontal while speeding up the mountain at up to 10m per second, reported The Guardian.

This will allow passengers to remain upright at all times, even as they ascend - or descend - the 1,720m track along gradients as steep as 110 per cent, or 47.7 degrees.

It will run from the valley station near Schwyz into the mountain village of Stoos, about 50km south of Zurich.

Mr Ivan Steiner, a spokesman for the railway, said the funicular replaced an older one that had operated since 1933.

"After 14 years of planning and building, everyone is very proud of this train," he said.