In the uneven terrain such as landfill, there are drainage ditches for draining rainwater. Width and depth of the ditch considerably varies depending on position in it. Therefore, it is important to choose appropriate position and approach angle toward the ditch for the car-like robot to traverse the ditch without slip or stuck. We have proposed a navigation method in which the car-like robot follows the straight line across the ditch to realize the appropriate position and approach angle using the path-generating regulator functionality. In this paper, we applied the method to an autonomous all-terrain vehicle and discussed the experimental results. We found out the following results. At the moment that the robot started to follow the straight line, if the magnitude of the attitude angle error to a target value was small, it was able to track the straight line before reaching the ditch. If not, it tended to be difficult to reach the ditch before reaching. We made some proposal for improvement about this issue as well.