In this paper, a unique method of deriving two kinds of models: simulation model and simplified control model for an arbitrary configuration of heavy vehicle (HV) system is proposed for the Automated Highway Systems (AHS). In the simulation model, each unit of a heavy vehicle system is considered as a free body with 6 degree of freedom unless constrained by the hitching mechanisms. The roll and pitch coupling due to constraints between connected units is investigated from the geometric point of view, and the dynamics of the hitching mechanisms are incorporated. A simplifed control model is obtained independent from the simulation model. By the proper application of Newtonian and Lagrangian mechanics to the different parts of the simplified model equations, the holonomic constraint forces are eliminated from the dynamic equations of motion. The control model is given in a closed form. As a special case, an open-loop simulation of tractor-semitrailer simulation model is presented.