Take the example of this crew leader. While he was loading cargo he bent down to release the lock on the dolly. Meanwhile, the driver of a TT started manoeuvring around a row of empty dollies that were left on the ramp. As the crew leader released the lock, he disappeared from the driver's line of sight. The TT nudged the dolly, knocking the crew leader to the ground.
Any empty dollies should have been moved earlier in the loading cycle and both the crew leader and the driver should have been watching out for each other.