Abstract: A side under ride guard for a large vehicle having a trailer portion with a relatively high ground clearance is provided. The trailer portion has a front, a rear, and opposing side edges extending between the front and the rear. The side under ride guard attaches to the trailer portion and is positioned below the side edge of the trailer portion a distance sufficient to obstruct progress of a passenger vehicle under the side edge of the trailer. The side under ride guard further is positioned relative to the side edge of the trailer so as to prevent intrusion of the side edge into the passenger vehicle occupant compartment as well as to minimize the regions of contact between the passenger vehicle and the side under ride guard itself.