Arousal level determination device

1. An arousal level determination device that determines an arousal level of a driver driving a vehicle, the arousal level determination device comprising:

a detection part configured to detect an amount of body movement indicating a magnitude of movement of a body of the driver; and

a determination part configured to determine the arousal level of the driver, wherein

the determination part determines that the driver is in an initial stage of decline in the arousal level when the amount of body movement has a decreasing trend, and

the determination part determines that the driver is in a progressive decline stage in the arousal level when the amount of body movement is changed from a decreasing trend to an increasing trend.

2. The arousal level determination device according to claim 1 , wherein

the detection part performs differential processing on an image obtained by imaging the driver along a time series to detect an amount of movement of the driver on the image as the amount of body movement.

3. The arousal level determination device according to claim 1 , further comprising:

a decision part configured to decide whether the determination part has determined the arousal level of the driver based on the amount of body movement based on at least one of a traveling state information of the vehicle and an operation information for the vehicle.

4. The arousal level determination device according to claim 3 , wherein

the decision part decides not to determine the arousal level of the driver when a vehicle speed of the vehicle is equal to or less than a predetermined threshold value.

5. The arousal level determination device according to claim 3 , wherein

the decision part decides not to determine the arousal level of the driver when a steering angle of the vehicle is larger than a predetermined threshold value.

6. The arousal level determination device according to claim 1 , wherein

the detection part corrects the amount of body movement by subtracting a value estimated as a magnitude of a movement caused by a driver's appropriate operation according to surrounding situation of the vehicle from the amount of body movement detected based on a magnitude of an actual movement of the driver.

7. The arousal level determination device according to claim 1 , wherein

the detection part corrects the amount of body movement by subtracting a value estimated as a magnitude of a movement of the driver caused by a behavior of the vehicle from the amount of body movement detected based on a magnitude of an actual movement of the driver.

8. The arousal level determination device according to claim 1 , wherein

the progressive decline stage is a stage that occurs after the initial stage of decline.

9. A computer-implemented method for determining an arousal level of a driver driving a vehicle, the computer-implemented method comprising:

detecting an amount of body movement indicating a magnitude of movement of a body of the driver; and

determining the arousal level of the driver, in which the driver is determined to be in an initial stage of decline in the arousal level based on the amount of body movement having a decreasing trend, and the driver is determined to be in a progressive decline stage in the arousal level based on the amount of body movement changing from a decreasing trend to an increasing trend.

10. The computer-implemented according to claim 9 , wherein

the progressive decline stage is a stage that occurs after the initial stage of decline.