a process of acquiring information on an environment around the vehicle, the information on the environment around the vehicle includes information on a state of a road after paving or covered with snow;

a process of acquiring information on a running state of the vehicle;

a process of generating a deviation boundary line such that the deviation boundary line is set at a position indicative of a boundary where a time-to-collision of the vehicle to a recognized object around the vehicle is a predetermined value or less;

an approach determination process of determining whether the vehicle is traveling in a direction to approach the deviation boundary line or not, where a posture of the vehicle faces the direction toward deviation boundary line and a speed of the vehicle is detected from the information on the running state;

a process of generating a reaction force to an operation on a steering device of the vehicle by a driver in the direction to approach the deviation boundary line such that the reaction force corresponds to a relative position of the vehicle to the deviation boundary line, the process being executed in a case where an affirmative determination is made in the approach determination process;

a first operation determination process of determining whether the operation on the steering device in a direction to separate from the deviation boundary line is performed or not;

a second operation determination process of determining whether or not an operation amount of the operation on the steering device in the direction to approach the deviation boundary line is equal to or more than a predetermined threshold; and

a process of controlling steering of the vehicle such that the vehicle does not cross the deviation boundary line, the process being executed in a case where an affirmative determination is made in the approach determination process and a negative determination is made in the first operation determination process and the second operation determination process.