TRAVEL ASSISTANCE METHOD AND TRAVEL ASSISTANCE DEVICE

The present invention provides a travel assistance method for performing a lane change of a host vehicle using a determined route and vehicle speed. The travel assistance method includes: detecting an oncoming vehicle traveling in an opposite lane opposite to a lane in which the host vehicle travels when the host vehicle starts the lane change; determining a crossing point between a virtual advancing route and a linear advancing route in which the oncoming vehicle advances linearly, the virtual advancing route differing from the route and being a virtual extension of an advancing route of the host vehicle in an advancing direction during a period from start to end of the lane change; executing a lane change using the route and the vehicle speed in a case where a time difference between a first predicted time when it is assumed that the host vehicle reaches the crossing point and a second predicted time until the oncoming vehicle reaches the crossing point is outside a predetermined range; and when the time difference is within the predetermined range, executing a lane change by changing at least one of the route and the vehicle speed such that the time difference is outside the predetermined range.