A system and method for using a gantry crane to efficiently and safely transport loads such as containers and ship hatch covers from one location to another along a known path while avoiding collisions between the loads and obstructing objects which may be situated in the known path. A transceiver emitting laser beams may be used to establish both the position of the spreader and its load and the profile of the known path. Continuous comparisons are made by computer between the location of a dynamic digital protective envelope constructed around the crane spreader and its load, if any, and a digital representation of the profile of the known path to be traveled by the spreader and its load, if any. In the event, the comparison indicates intersection of the protective envelope and the path profile, a speed limit is imposed on the motor controlling the movement in the X axis of the trolley or in the Z axis of the spreader, as required to prevent a collision.