Driving assistance apparatus and driving assistance apparatus processing method

A driving assistance apparatus for performing vehicle speed assist control for driving a host vehicle at a predetermined set vehicle speed, the apparatus comprising:

• a memory storing a program;
• and
• a processor configured to execute the program to:
• determine whether a roundabout has been detected in front of the host vehicle based on a captured image of a front camera of the host vehicle, or position information of the host vehicle and map information,
• acquire lane widths of a plurality of lanes in a case where a road on which the host vehicle travels toward the roundabout includes the plurality of lanes,
• acquire a curvature of the roundabout based on the captured image of the front camera or the position information and the map information,
• when the road on which the host vehicle travels has four or more lanes and the curvature of the roundabout is equal to or greater than a predetermined value, acquire an entrance width of the roundabout based on only two of the four or more lanes that are closest to a center of the road as an entrance of the roundabout;
• calculate, for each of the plurality of lanes including a traveling lane of the host vehicle, a lane width passing time in which an other vehicle traveling on the roundabout passes a lane width, based on the captured image of the front camera, wherein the lane width passing time includes a time until a tip of the other vehicle passes across lane lines for each of the plurality of lanes;
• estimate, for each of the plurality of lanes, a lane-corresponding vehicle speed of the other vehicle based on the entrance width and the lane width passing time, and calculate a weighted mean of the lane-corresponding vehicle speeds, wherein a weight assigned to the lane-corresponding vehicle speed for the traveling lane of the host vehicle is greater than weights assigned to the lane-corresponding vehicle speeds for other lanes;
• and
• set a set vehicle speed for the host vehicle to travel on the roundabout based on the weighted mean of the lane-corresponding vehicle speeds.