The optimum steady-state response of a tractor-semitrailer vehicle traveling over an uneven road is considered. A mathematical programming technique of the design of a tractor-semitrailer suspension system is formulated. The mathematical model is excited at more than one point by harmonic forces.The objective of the optimization problem is to find the optimum suspension parameters that provide sufficient vibration isolation from road disturbances so that desired level of driver comfort can be achieved, in a given frequency interval.The design criterion for measuring the desired level of ride quality is the maximum acceleration at the cab. The design is subjected to a constraint upon maximum fore and aft acceleration caused by the articulation. It is also constrained by requiring maximum values for the static deflections of the suspensions.The mathematical techniques and the corresponding numerical solution of the governing differential equations are presented and an optimization algorithm is chosen to select the optimum design.