Vehicle travel control method and travel control device

1. A travel control method for a vehicle for executing autonomous lane change control of the vehicle when, before performing the autonomous lane change control, presenting a driver with lane change information as to whether or not to accept execution of the autonomous lane change control and detecting, in response to presentation of the lane change information, an acceptance input made by the driver indicating that the driver accepts the execution of the autonomous lane change control, the travel control method comprising:

upon execution of autonomous control of two or more successive lane changes,

before performing the two or more successive lane changes, presenting the driver with first lane change information as to whether or not to accept the execution of the autonomous control of the two or more successive lane changes;

when detecting, in response to presentation of the first lane change information, a first acceptance input made by the driver indicating that the driver accepts the execution of the autonomous control of the two or more successive lane changes, executing first autonomous lane change control;

after executing the first autonomous lane change control, presenting the driver with second lane change information as to whether or not to accept execution of the autonomous lane change control after the first lane change; and

when detecting, in response to presentation of the second lane change information, a second acceptance input made by the driver indicating that the driver accepts the execution of the autonomous lane change control after the first lane change, executing the autonomous lane change control after the first lane change,

wherein an action load of the second acceptance input is set smaller than an action load of the first acceptance input.

2. The travel control method for a vehicle according to claim 1 , comprising:

detecting the first acceptance input with a predetermined input operation made by the driver; and

detecting the second acceptance input with an operation in which the driver makes no input.

3. The travel control method for a vehicle according to claim 2 , wherein

the first lane change information is information for encouraging to execute a predetermined input operation when accepting the autonomous control of the two or more successive lane changes, and

the second lane change information is information for encouraging to execute a predetermined input operation when not accepting the autonomous lane change control after the first lane change.

4. The travel control method for a vehicle according to claim 1 , comprising:

detecting the first acceptance input with a predetermined input operation that is made by the driver and involves a directional property of changing lanes; and

detecting the second acceptance input with an input operation that is made by the driver and does not involve the directional property of changing lanes.

5. The travel control method for a vehicle according to claim 1 , comprising:

detecting the first acceptance input with a predetermined number of input operations made by the driver; and

detecting the second acceptance input with a smaller number than the predetermined number of input operations made by the driver.

6. The travel control method for a vehicle according to claim 1 , comprising:

presenting the second lane change information before the vehicle completes the first autonomous lane change control.

7. The travel control method for a vehicle according to claim 1 , comprising:

presenting the second lane change information after the vehicle completes the first autonomous lane change control.

8. The travel control method for a vehicle according to claim 1 , wherein

the second acceptance input includes an acceptance input as to whether or not to accept (n+1)-th autonomous lane change control after the first autonomous lane change control and an acceptance input as to whether or not to accept (n+2)-th autonomous lane change control where n is a natural number, and

the action load of the acceptance input as to whether or not to accept the (n+2)-th autonomous lane change control is set equal to or smaller than the action load of the acceptance input as to whether or not to accept the (n+1)-th autonomous lane change control.

9. The travel control method for a vehicle according to claim 1 , comprising:

when not detecting the first acceptance input made by the driver, prohibiting execution of the first autonomous lane change control; and

when not detecting the second acceptance input made by the driver, prohibiting execution of the autonomous lane change control after the first lane change.

10. A travel control apparatus for a vehicle for executing autonomous lane change control of the vehicle when, before performing the autonomous lane change control, presenting a driver with lane change information as to whether or not to accept execution of the autonomous lane change control and detecting, in response to presentation of the lane change information, an acceptance input made by the driver indicating that the driver accepts the execution of the autonomous lane change control, the travel control apparatus operating to:

upon execution of control of two or more successive lane changes,

before performing the two or more successive lane changes, present the driver with first lane change information as to whether or not to accept the execution of the control of the two or more successive lane changes;

when detecting, in response to presentation of the first lane change information, a first acceptance input made by the driver indicating that the driver accepts the execution of the control of the two or more successive lane changes, execute first autonomous lane change control;

after executing the first autonomous lane change control, present the driver with second lane change information as to whether or not to accept execution of the autonomous lane change control after the first lane change; and

when detecting, in response to presentation of the second lane change information, a second acceptance input made by the driver indicating that the driver accepts the execution of the autonomous lane change control after the first lane change, execute the autonomous lane change control after the first lane change,

wherein an action load of the second acceptance input is set smaller than an action load of the first acceptance input.