Driving assistance apparatus

1. A driving assistance apparatus for a vehicle, comprising:

a grip state detection section configured to detect a grip state of a steering wheel in a compartment of the vehicle;

an image acquisition section configured to acquire a captured image of the compartment that covers a possible action range of a person who is seated in a driver's seat;

a position specification section configured to specify, based on a captured image acquired by the image acquisition section, a position where a non-grip hand exists, the non-grip hand being a hand that is separate from the steering wheel, on condition that (i) the grip state of the steering wheel is in a hand-free state, in which at least either of two hands is separate from the steering wheel as a result of detecting of the grip state detection section, and (ii) a travel state of the vehicle is within a stipulated travel state, which is predetermined;

a danger derivation section configured to derive a danger degree such that the danger degree comes to have a greater value as a degree of a danger against driving of the vehicle becomes higher because the non-grip hand exists in a position specified by the position specification section; and

a warning section configured to execute an output of a warning in a weaker state as the danger degree derived by the danger derivation section comes to have a smaller value,

wherein:

the danger derivation section

classifies a plurality of positions in the compartment in the vehicle based on danger degrees, and

defines previously a low danger position within the positions classified, wherein the danger degree has a value smaller than a reference value when the non-grip hand exists in the low danger position; and

the danger derivation section derives the danger degree such that when the non-grip hand exists in the low danger position, the danger degree has a value smaller as compared with a case that the non-grip hand exists in a high danger position, which is within the positions classified in the compartment and is other than the low danger position.

2. The driving assistance apparatus according to claim 1 , wherein

the danger derivation section derives the danger degree such that the danger degree comes to have a smaller value as a non-grip hand existence duration for which the non-grip hand continues to exist in the low danger position becomes shorter.

3. The driving assistance apparatus according to claim 2 , wherein

the danger derivation section derives the danger degree such that when the non-grip hand existence duration relative to the low danger position, where the non-grip hand exists, is shorter than a predetermined value, the danger degree has a minimum value.

4. The driving assistance apparatus according to claim 1 , wherein

the danger derivation section derives the danger degree such that when the non-grip hand exists in the high danger position, the danger degree comes to have a greater value as a non-grip hand existence duration, for which the non-grip hand continues to exist in the high danger position, becomes longer.

5. The driving assistance apparatus according to claim 1 , wherein

the danger derivation section derives the danger degree such that when the non-grip hand exists in the high danger position, the danger degree comes to have a greater value as the high danger position is farther away from the driver's seat.

6. The driving assistance apparatus according to claim 1 , wherein:

the high danger position is a position, where a target object manipulated by the non-grip hand exists; and

the danger derivation section derives the danger degree such that when the non-grip hand exists in the high danger position, the danger degree comes to have a greater value as a duration, for which the non-grip hand manipulates the target object in the high danger position and then grips the steering wheel, is estimated to become longer.

7. The driving assistance apparatus according to claim 1 , wherein:

the high danger position is a position where a target object manipulated by the non-grip hand exists; and

the danger derivation section derives the danger degree such that when the non-grip hand exists in the high danger position, the danger degree comes to have a greater value as a duration, for which the driver moves a sight line away from a heading direction of the vehicle when manipulating the target object in the high danger position, is estimated to become longer.

8. The driving assistance apparatus according to claim 1 , wherein

the position specification section

determines whether a position where the non-grip hand exists is the low danger position, and

defines a high danger position, which is within the positions classified in the compartment and is determined not to be the low danger position.

9. The driving assistance apparatus according to claim 1 , wherein

The danger derivation section defines as the low danger position, at least one of (i) an armrest provided in the vehicle, (ii) a window frame in the vehicle, and (iii) a driver's upper thigh.

10. The driving assistance apparatus according to claim 1 , wherein

the warning section prohibits an output of a warning when the danger degree derived by the danger derivation section is equal to or less than a predetermined value.

11. The driving assistance apparatus according to claim 1 , wherein

the stipulated travel state includes a travel state where the hand-free state during driving of the vehicle is evitable.

12. A program product, stored in a non-transitory computer readable storage medium, comprising instructions for execution by a computer, the instructions including a computer-implemented method in a driving assistance apparatus for a vehicle for deriving a danger degree to warn against driving manipulation of the vehicle, the driving assistance apparatus including:

a grip state detection section configured to detect a grip state of a steering wheel in a compartment of the vehicle; and

an image acquisition section configured to acquire a captured image of the compartment that covers a possible action range of a person who is seated in a driver's seat,

the instructions for implementing the steps of:

specifying, based on a captured image acquired by the image acquisition section, a position where a non-grip hand exists, the non-grip hand being a hand that is separate from the steering wheel, on condition that (i) the grip state of the steering wheel is in a hand-free state, in which at least either of two hands is separate from the steering wheel as a result of detecting of the grip state detection section, and (ii) a travel state of the vehicle is within a stipulated travel state, which is predetermined;

deriving a danger degree such that the danger degree comes to have a greater value as a degree of a danger against driving of the vehicle becomes higher because the non-grip hand exists in the position specified; and

executing an output of a warning in a weaker state as the danger degree derived comes to have a smaller value, wherein

in the deriving step,

a plurality of positions are classified in the compartment in the vehicle based on danger degrees, and

a low danger position is defined previously within the classified positions, wherein the danger degree has a value smaller than a reference value when the non-grip hand exists in the low danger position; and

in the deriving step,

the danger degree is derived such that when the non-grip hand exists in the low danger position, the danger degree has a smaller value as compared with a case that the non-grip hand exists in a high danger position, which is within the positions classified in the compartment and is other than the low danger position.