TRAVEL CONTROLLER, METHOD FOR TRAVEL CONTROL, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM CONTAINING COMPUTER PROGRAM FOR TRAVEL CONTROL

A travel controller detects a vehicle traveling behind a host vehicle from situation data depending on the situation around the host vehicle; controls travel of the host vehicle to maintain a predetermined distance or more between the host vehicle and the detected vehicle behind; causes the host vehicle to perform a first action when the distance between the host vehicle and the vehicle behind is greater than a distance threshold; causes the host vehicle to perform a second action when the distance is less than the distance threshold, the second action contributing to safe travel of the host vehicle more than the first action; sets the distance threshold at a first value when a travel situation around the host vehicle does not satisfy a predetermined short-distance condition; and sets the distance threshold at a second value smaller than the first value when the travel situation satisfies the short-distance condition.