Travel Assistance Method and Travel Assistance Device

A travel support method for a vehicle comprises estimating a position of a subject vehicle, generating a subject vehicle traveling route, based on the estimated position of the subject vehicle and map information, calculating a degree of first reliability indicating reliability of the subject vehicle traveling route, detecting a preceding vehicle traveling ahead of the subject vehicle, generating a preceding vehicle traveling route, calculating a degree of second reliability indicating reliability of the preceding vehicle traveling route, based on the preceding vehicle traveling route, calculating, based on the degrees of the first reliability and second reliability, an integration ratio for integrating the subject vehicle traveling route and the preceding vehicle traveling route, calculating a target traveling route of the subject vehicle by integrating the subject vehicle traveling route and the preceding vehicle traveling route at the integration ratio, and controlling the subject vehicle based on the target traveling route.