It is not only the major cities and business centers which are constantly faced with a collapse of the traffic system. Far away from the major metropolises, small towns and localities suffer under the impact of through traffic, noise and exhaust fumes. Conditions alike these were also experienced around the North Italian city of Trento, capital of the Trentino-South Tyrol region, where in the northern foothills the congested SS 47 national road pushes its way eastwards towards the A 22. To relieve these localities – particularly of heavy goods traffic – the Provinzia Autonomina di Trento decided on the construction of a new bypass. The core of the bypass revolves around two 2,760-meter-long tunnels bored through the Dolomites.
From mid-February 2004 a Herrenknecht Single Shield TBM worked its way through limestone, loam and sandy formations with ever-increasing advancing rates for the two-lane road tunnel. Starting in the small locality of St. Martignano, the 127-meter-long mobile tunnel factory of a 3,600-kW capacity drove the tunnels (11-meter inside diameter) on the mountain side and lined them with segments. After completing the first tunnel, the machine was turned round to excavate the parallel-running tube in the opposite direction at a distance of eight meters. The project was finished in December 2005.