Tran and Ha 2008 : On-line prediction of unmanned ground vehicle (UGV) behaviour during interactions with terrain is essential for autonomous and safe operations of skid-steering UGVs. This paper presents a fast and accurate algorithm for a new interaction model to predict performance of a UGV running on a particular terrain. By approximating nonlinear relations involved in the interaction between the vehicle and terrain, a closed form of the interaction model is obtained to enable on-line computation. The minimum absolute error criteria are applied to secure accuracy for the proposed method. The development is compared with the other models in terms of both computation speed and accuracy.