843.019 passed Varenzo, north of Rodi-Fiesso, with a rescue train on the afternoon of 11 August 2016. The same loco and train had passed in the opposite direction a few hours earlier.
Diesel powered rescue trains are stationed on the Gotthard, just in case there’s a major incident inside one of the tunnels. They probably get bored just sitting waiting for something to happen, so every now and again the diesel takes them for a run down the mountain and back again to keep their spirits up.