In this paper, we propose a feedforward compensation method to enhance the performance of the lateral guidance system of heavy vehicles on automated highway systems (AHS). The feedforward controller blends well with the linear robust feedback controller. The proposed feedforward compensation is motivated by the analogy between a vehicle lateral control system on curved roads and a mechanical system with Coulomb friction. The sliding mode controller for vehicle lateral guidance is shown to inherently involve a feedforward compensation term. Performance of a tractor-semitrailer combination vehicle under linear robust feedback control is used as the base line to show by simulations the enhancement of performance by fixed gain and adaptive feedforward controllers. The tracking performance is further improved by sliding mode control. In view that the sliding mode controller is more complex than the linear controller, the combination of the linear feedback controller and the feedforward controller is at a mid-point between ease of implementation and control performance.