Since the lateral control problem for heavy vehicles (HVs) consists of lane following and lane changing, switching between these operating modes gives the closed-loop system a hybrid nature. The lateral controller is designed using H_infinity loop-shaping method to ensure the robust performance under model uncertainties. It is designed to regulate the lateral deviation of the sensor output to zero under a lane following mode or make the lateral deviation to track a desired trajectory under a lane changing maneuver. Discrete states are given to represent different closed-loop systems for different operating modes. Worst case simulations are conducted to give the reachable sets for the lateral deviations on both nominal and perturbed plants. The results show that the reachable sets are in the safe region where the difference between the desired lateral deviation and the real lateral deviation is less than 0.2 m in consideration of the limit lane width and physical geometry of HVs.