Travel assistance method and travel assistance apparatus

1. A travel assistance method that is performed by a computer including at least one processor, the travel assistance method assisting travel of a subject vehicle and comprising:

setting a start point and an end point of a route where the subject vehicle travels along a curve;

assuming a triangle in which a remaining vertex is determined such that the triangle is formed by the start point, the remaining vertex and the end point;

setting a control point on each of two sides of the triangle to determine a quadrangle including the two control points, the start point, and the end point as four vertexes;

calculating a route line accommodated in the quadrangle; and

assisting the subject vehicle in traveling along the curve following the route line,

wherein:

assisting the subject vehicle in traveling along the curve following the route line includes turning right or left at an intersection;

the travel assistance method further comprises acquiring position information of a no-entry area within the intersection; and

the quadrangle is determined by setting the control points so as to cause a distance between a line segment connecting the control points and the no-entry area to be larger than or equal to a a threshold.

2. The travel assistance method according to claim 1 , wherein:

assisting the subject vehicle in traveling along the curve following the route line includes turning right or left at an intersection; and

at the assuming of the triangle, the remaining vertex of the triangle is located at an intersection point of a half line extending from the start point in a direction of entering the intersection and a half line extending from the end point in an opposite direction to a direction of exiting the intersection.

3. The travel assistance method according to claim 1 , wherein:

assisting the subject vehicle in traveling along the curve following the route line includes turning right or left at an intersection; and

the travel assistance method further comprises setting a waiting position of the subject vehicle on the route line at a position nearer to the start point than a position where the route line crosses an opposite lane.

4. The travel assistance method according to claim 1 , wherein:

assisting the subject vehicle in traveling along the curve following the route line includes turning right or left at an intersection; and

the travel assistance method further comprises

determining the route line as a first route line,

determining the start point as a first start point,

determining a second start point on the first route line straightforward away from the first start point by a predetermined distance,

calculating a second route line passing the second start point, and

setting a waiting position between the first start point and the second start point, the waiting position being for a case of travelling the second route line.

5. The travel assistance method according to claim 4 , further comprising,

determining whether an oncoming vehicle exists,

wherein,

at the assisting of the subject vehicle in traveling along the curve,

in response to a determination that no oncoming vehicle exists, the travel of the subject vehicle along the curve following the first route line is assisted, and

in response to a determination that the oncoming vehicle exists, the travel of the subject vehicle along the curve following the second route line is assisted.

6. The travel assistance method according to claim 4 , further comprising:

determining whether an opposite lane exists; and

suspending calculation of the second route line in response to a determination that no opposite lane exists.

7. The travel assistance method according to claim 1 , wherein:

assisting the subject vehicle in travelling along the curve following the route lines includes changing lanes;

the travel assistance method further comprises

setting a departure point and an arrival point for lane change, and

setting a passing point where the subject vehicle passes on a line connecting the departure point and the arrival point;

at the setting of the start point and the end point, the departure point is set as a first start point, the passing point is set as a first end point and also as a second start point, and the arrival point is set as a second end point;

at the assuming of the triangle, a first triangle including the first start point, the first end point, and a point on a half line extending forward from the first start point in a traveling direction as three vertexes is assumed, and a second triangle including the second start point, the second end point, and a point on a half line extending backward from the second end point in the traveling direction as three vertexes is also assumed; and

at the calculating of the route line, a first route line between the first start point and the first end point is calculated, and a second route line between the second start point and the second end point is also calculated.

8. The travel assistance method according to claim 7 , further comprising:

determining whether a half line extending forward from the departure point in a traveling direction crosses a half line extending backward from the arrival point in the traveling direction; and

calculating the route line in which the departure point is the start point and the arrival point is the end point in response to a determination that the half lines cross each other.

9. The travel assistance method according to claim 8 , wherein,

the calculating of the route line is performed to calculate the first route line and the second route line in response to a determination that the half lines do not cross each other at the determining whether the half lines cross each other.

10. The travel assistance method according to claim 7 , further comprising,

calculating a cancel route line in which the subject vehicle changing lanes returns from the route line to a travel route before the lane change.

11. A travel assistance apparatus comprising:

a point setting section that sets a start point and an end point of a route when a subject vehicle travels along a curve and assumes a triangle in which a remaining vertex is determined such that the triangle is formed by the start point, the remaining vertex and the end point;

a route line calculation section that sets a control point on each of two sides of the triangle to determine a quadrangle including the two control points, the start point, and the end point as four vertexes, and the route line calculation section calculates a route line accommodated in the quadrangle; and

a curve assistance section that assists the subject vehicle in traveling along the curve following the route line,

wherein:

assisting the subject vehicle in traveling along the curve following the route line includes turning right or left at an intersection;

the point setting section is configured to acquire position information of a no-entry area within the intersection; and

the quadrangle is determined by setting the control points so as to cause a distance between a line segment connecting the control points and the no-entry area to be larger than or equal to a threshold.

12. A travel assistance apparatus comprising:

at least one processor connected to a memory,

wherein:

the at least one processor sets a start point and an end point of a route when a subject vehicle travels along a curve and assumes a triangle in which a remaining vertex is determined such that the triangle is formed by the start point, the remaining vertex and the end point;

the at least one processor sets a control point on each of two sides of the triangle to determine a quadrangle including the two control points, the start point, and the end point as four vertexes, and the at least one processor calculates a route line accommodated in the quadrangle; and

the at least one processor assists the subject vehicle in traveling along the curve following the route line, causing the subject vehicle to follow the route line,

wherein:

assisting the subject vehicle in traveling along the curve following the route line includes turning right or left at an intersection;

the at least one processor further configured to acquire position information of a no-entry area within the intersection; and

the quadrangle is determined by setting the control points so as to cause a distance between a line segment connecting the control points and the no-entry area to be larger than or equal to a threshold.