The Gemmenich Tunnel (, ) passing under the "" (Three country point) has a special track layout to enable the passage of wide military loads. The double-track tunnel has a third set of rails interlaced with one of the normal tracks. Active points (switches) at each end of the tunnel allow a train to divert along the central track, whilst other trains are blocked by signalling. The third track is rarely in use, so there is no limitation of capacity through the tunnel for standard-sized trains.