Robotic automation and methods described herein can be used to enhance the efficiencies of freight shipping processes. For example, this document describes the use of automated systems and methods for densely loading cargo into freight carriers (e.g., semi-trailers) in an efficient manner. Some such systems can include one or more movable robots that can travel along an open side or open top of a semi-trailer to autonomously load parcels into the trailer in a densely packed manner. The disclosed systems and methods allow for the reduction or elimination of manual labor for loading shipping trailers in a very dense manner.