unit director  Yakima Canutt (qv), the "Messala" that was run over, a Roman  soldier standing on the center island who was hit by a chariot and  the driver of a spilled rig who jumped out of the way of one chariot  but was immediately run over by another one were all articulated and  weighted dummies (made with movable arm and leg joints), so when  they were hit they "reacted" the way a normal human body would in  that situation. A combination of adroit placement and expert editing  made the dummies look like real people being run over.