In many projects, like the Simplon, for example, a small pilot tunnel is driven before the full diameter of the tunnel is excavated. 在许多隧道工程中，经如辛普龙大隧道，都要在隧道全面开挖前打一个导洞。
Actually it is not so far from Bad Gastein to Heiligenblut, but there is only one big tunnel connecting these two places, so only taking the train can reach the destination. 其实从巴得嘎斯坦到海立根布鲁特不是很远，但只有一条大隧道将两地连接在一起，所以非乘火车不可。
