The Bernina line of the Rhaetian Railway is the highest crossing of the Alps by a railroad and is largely an open line. The highest station is Ospizio Bernina at 2253 meters above sea level. In heavy snowfall and particularly windy conditions, individual scheduled passenger trains are preceded by so-called track plows, which can throw out snow from the track up to several centimetres below the top of the rails. These plows of type Xk # 9141 to # 9147 were built by Stadler between 1966 and 1988. They can be used in both directions of travel. The plows at the front and rear are permanently mounted, the one in the middle of the vehicle can be raised and lowered hydraulically, which is done via radio remote control from the driver's cab of the pushing traction unit. For this purpose, a railroad service employee sits next to the driver with the remote control. The mobile plow must be raised when driving over switches and level crossings to prevent damage or even derailment. To do this, the speed is reduced slightly and the operator of the plow is highly concentrated. The maximum velocity when used this track plow is 40 km/h. This is not very restrictive, as the line speeds on the mountain section are mostly between 30 and 45 km/h, and only on individual shorter sections is the maximum 65 km/h. Regional train 4621 of the line R19 from St.Moritz to Tirano is rounding the more then 180 degree "panorama curve" when leaving Alp Grüm, shoving the track plow Xk # 9143 in front of the "Allegra" ABe 8/12 # 3509. The maximum velocity in this curve with a radius of 45 meter only is 30 km/h.
