Controller and control method of rider support system

A control method for a rider support system (1), the rider support system (1) configured to assist a rider in driving a motorcycle (100), the control method comprising:

• acquiring, using a controller (20), a surrounding environment information while the motorcycle (100) travels, the surrounding environment information that is information about an environment surrounding the motorcycle;
• and
• causing, using the controller (20), the motorcycle (100) to execute an adaptive cruise control operation based on the surrounding environment information acquired by the the controller (20), wherein
• the controller (20) is configured to cause the motorcycle (100) to execute
• a first operation as the adaptive cruise control operation when a group ride mode in which the motorcycle (100) travels together with at least one motorcycle (200) in a group is inoperable;
• and
• a second operation as the adaptive cruise control operation when the group ride mode is operable, the second operation is different from the first operation, and
• the controller (20) is configured to cause a notification device (50) to provide different notifications in the first operation and the second operation respectively, wherein the notification is given to the rider.