Trailers and semi-trailers for road freight operate under extreme dynamic loads that cause fatigue damage, deformation and structural failure. This review synthesises the literature on the structural optimisation of truck, trailer and semi-trailer structures under such loads, based on a targeted, iterative search of two databases and three publisher platforms, extended by citation chaining, that yielded 68 primary studies. The studies are grouped into three method families (topology, parametric and artificial intelligence (AI)-assisted optimisation) and compared by outcome, type of redesign and validation level. Same-material optimisations of complete frames and components save about 7–16% of mass, with or without tests; the largest values, 28% for steel longitudinal beams and a theoretical 67% for a fully composite trailer, come from beam shape optimisation and composite substitution in one numerical study. A coverage map of 56 scored studies shows that more than half do not consider time-varying loads, that fatigue, buckling and fail-safe criteria are rarely optimised together, and that optimised designs are seldom tested, while advanced formulations are demonstrated mostly on generic structures. The review proposes minimum safeguards for AI-assisted design, discusses manufacturability and economic feasibility, and outlines an integrated workflow linking measured load spectra, multi-criteria optimisation and staged experimental validation.