Driving assist system

1. A driving assist system that assists driving of a vehicle, the driving assist system comprising:

a memory configured to store driving environment information indicating a driving environment for the vehicle; and

a processor configured to execute driving assist control including at least one of deceleration control and steering control for avoiding a collision with a target ahead of the vehicle based on the driving environment information, wherein

the driving assist control operates when the target exists within an assist area and does not operate when the target exists outside the assist area,

a roadway area in which the vehicle exists is an area between a first roadway boundary located on a first side as viewed from the vehicle and a second roadway boundary located on a second side opposite to the first side as viewed from the vehicle,

a crossing target is the target that crosses the roadway area ahead of the vehicle from the first side toward the second side,

the processor is further configured to divide the assist area for the crossing target into a plurality of divided assist areas based on a direction of movement of the crossing target,

the plurality of divided assist areas include a first assist area located on the first side as viewed from the vehicle and a second assist area located on the second side as viewed from the vehicle,

the processor is further configured to determine in which of the plurality of divided assist areas the crossing target exists, and to execute the driving assist control with a control strength according to a result of the determination, and

when the crossing target exists in the second assist area of the roadway area, the processor decreases the control strength of the driving assist control as compared with a case where the crossing target exists in the first assist area based on the direction of movement of the crossing target from the first side towards the second side, wherein

the control strength of the driving assist control includes a magnitude of an assist control amount including a deceleration in the deceleration control and a steering angle in the steering control,

the assist control amount is expressed as a function of a relative relationship parameter including a relative position and a relative speed between the vehicle and the target, and

decreasing the control strength includes reducing the assist control amount corresponding to the same relative relationship parameter.

2. The driving assist system according to claim 1 , wherein

the processor is further configured to set a risk area around the crossing target and to execute the driving assist control such that the vehicle avoids the risk area,

the control strength of the driving assist control includes a size of the risk area, and

decreasing the control strength includes narrowing the risk area.

3. The driving assist system according to claim 1 , wherein

the plurality of divided assist areas further include a center assist area between the first assist area and the second assist area, and

when the crossing target exists in the first assist area or the second assist area, the processor decreases the control strength of the driving assist control as compared with a case where the crossing target exists in the center assist area.

4. The driving assist system according to claim 3 , wherein

the deceleration control when the crossing target exists in the center assist area is set at a default deceleration.

5. The driving assist system according to claim 3 , wherein the processor is further configured to set a first dividing boundary of the center assist area at a position apart from a first nearby lane marking toward the first side by a first distance and set a second dividing boundary at a position apart from a second nearby lane marking toward the second side by a second distance.

6. The driving assist system according to claim 1 , wherein

each of the first assist area and the second assist area is further divided into a nearby assist area and a distant assist area,

the nearby assist area is located between the vehicle and the distant assist area in a direction of travel of the vehicle, and

when the crossing target exists in the distant assist area, the processor decreases the control strength of the driving assist control as compared with a case where the crossing target exists in the nearby assist area.