This work describes the design and testing of side underride protection devices (SUPD) for tractor-trailers and straight trucks. Its goal is to reduce the incompatibility between small passenger cars and these large vehicles during side collisions. The purpose of these crash attenuating guards is to minimize occupant injury and passenger compartment intrusion. The methods presented utilize a regulation previously created and published for testing the effectiveness of these devices based on the principles of a force application device already implemented in the Canadian rear underride guard regulation. Topology and multi-objective optimization design processes are outlined using a proposed design road map to create the most feasible SUPD. The test vehicle in question is a 2010 Toyota Yaris which represents the 1100C class of vehicle from the Manual for Assessing Safety Hardware (MASH). Since the tractor-trailers and straight trucks utilize different structural components, separate concepts must be generated to accommodate each individual application. The LS-DYNA software package is employed for the creation of the devices, the simulations and the optimization. The guards are tested and their performance is evaluated in order to examine their benefits during collisions.