As early as 1947, engineer Eduard Gruner imagined a two-story base tunnel from Amsteg to Biasca, both rail and road, with a stop at Sedrun, to provide a faster and flatter passage through the Swiss Alps. Similarly to Gruner's idea, the GBT cuts through the Gotthard Massif some below the older tunnel. On the historic track the Gotthard Railway only trains up to when using two locomotives or up to with an additional bank engine at the end of the train are able to pass through the narrow mountain valleys and through spiral tunnels climbing up to the portals of the old tunnel at a height of above sea level. Since the GBT is in full service, standard freight trains of up to are able to pass this natural barrier.