Many researchers have tried to study the effect of preview sensors or time delay on suspension system performance using quarter car models. This paper is directed to study the effect of road and wheelbase preview sensors on the performance of the active suspension system performance using a longitudinal have vehicle model. The road input is assumed to be measured at a certain distance in front of the have vehicle. Optimal control theory is used to formulate the problem and the resulting equations of motion are solved by using Pade approximations. Results are obtained in terms of body accelerations, suspension working space and dynamic tyre load for either the front or rear wheel. The results indicate that there are some improvements hich can be gained hen the heelbase preview is modelled. On the other hand, a significant improvement is obtained when the wheelbase and road preview sensors are included in the half vehicle model.