Travel assistance method and travel assistance device

A travel assistance device comprising:

• a sensor equipped in a subject vehicle;
• and a processor for executing a control process for supporting the travel of the subject vehicle, the processor is configured to:
• set a travel lane in which the subject vehicle travels based on detection information of the sensor;
• identify a preceding vehicle traveling ahead of the subject vehicle in the travel lane based on the detection information of the sensor;
• calculate, based on the detection information, a first evaluation value indicating a possibility that the subject vehicle can return to the travel lane from an adjacent lane adjacent to the travel lane after overtaking the preceding vehicle;
• calculate a shortening width of travel time shortened by overtaking the preceding vehicle based on a vehicle speed of the subject vehicle and a vehicle speed of the preceding vehicle;
• calculate a shortening width evaluation value comparable to the first evaluation value according to the shortening width;
• compare the first evaluation value with the shortening width evaluation value;
• and
• determine whether or not to overtake the preceding vehicle based on a result of comparison.