The unloading station includes a door moving mechanism for moving the doors of the vehicle to the open position upon {HEAD ~ its arrival} at {TAIL ~ the station} 
at
The unloading station includes a door moving mechanism for moving the doors of the vehicle to the open position upon { HEAD ~ its arrival } at { TAIL ~ the station }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL