Abstract
A nonlinear stability analysis of a steady state horizontal and downhill straight line motion of a controlled truck- trailer system is given. Special emphasis is given to the modelling of the controller simulating the steering actions of the driver. The two different types of controllers both including the effect of the reaction time of the driver are used. The basic question to be answered is whether the truck- trailer system after loss of stability of the steady state still is controlable by the driver or not. I.E. Whether after loss of stability nearby stable states exist or not. A question which can only be answered by a nonlinear analysis. The answer is given for the variation of a number of parameters.