The dynamic response of a highway tractor-trailer to a nuclear overpressure loading is much different than the vehicle's response to the usual static and road transport design loads. The nature of the overpressure loads and that of the response of the tractor-trailer are discussed. A nonlinear transient NASTRAN analysis calculates the response of a vehicle to blast pressures. The kingpin, between the tractor and trailer, responds nonlinearly to high lateral blast loads that try to overturn the vehicle. Shelters are mounted to the trailer with flexible isolators, which are also nonlinear for the high loads during a nuclear blast. The techniques used to model the nonlinear components and to include the static initial conditions are described. Design modifications, shown by analysis to be necessary, resulted in an acceptable design. In conclusion, the design considerations for tractor trailers under overpressure loads are discussed.