Great Journeys Of New Zealand's "Tranz Alpine" arriving into Arthurs Pass Station. Due to the 1:33 gradient of the Otira Tunnel banker engines are required to be added to the front of all east bound trains, but the Tranz Alpine is different, due to safety reasons the Tranz Alpine is banked in both directions, and two bankers are attached to the front and two are attached to the rear. Here we see the Tranz Alpine emerging from the Otira Tunnel and arriving into Arthurs Pass station where the banker engines are removed, before continuing the journey back to Christchurch.