This research focused on the SAE level 3 and 5 of autonomous driving system. The purpose of this research clarified the driving characteristics when the vehicle control change from the system to manual driving. Two experiments were carried out in order to clarify the characteristics of manual driving in this situation. The first experiment was a lane change situation in the merging lane, and the other vehicles merge into the lane which the host vehicle is driving from the left side of highway intersection. This experiment focused on the level 3 of system, and the driver was the low alertness situation. This experiment simulated the functional limit of the system. When the forward vehicle changed the lane in front of the host vehicle, the driving task changed from the system to the driver. The second experiment was a situation that the driver drives the city road with manual driving after the driver used the system in a state of sleep on highway. In this experiment, a pedestrian rushes out from the blind spot in the city road, the driver should carry out the emergency braking action after the driver awaked from the sleeping. In the first experiment, the driver cannot respond to control the vehicle when the driving task change from the system as the low alertness situation. In the second experiment, the timing of braking action was long, and the driver's brake pedal force decreased. As the results, (1) The autonomous driving system has to detect the driver’s state, and the system has to activate the warning which notify the driver the changing of the driving task (level 3). (2) If the driver use this system in a state of sleep, the driving task change to manual driving after the driver awake from the sleeping completely (Level 5).