Warning system

1. A warning system, comprising:

an angle-detector that indicates a steering-angle of a hand-wheel of a host-vehicle;

a curvature-detection-means that detects a curvature of a portion of a roadway traveled by the host-vehicle, said portion characterized as ahead of the host-vehicle in a current direction of travel;

an alert-device; and

a controller-circuit in communication with the angle-detector, the curvature-detection-means, and the alert-device, the controller-circuit configured to:

determine an average-steering-angle in accordance with the steering-angle indicated by the angle-detector;

determine an expected-steering-angle based on the curvature detected by the curvature-detection-means;

determine a steering-angle-deviation based on the average-steering-angle and the expected-steering-angle;

determine whether the steering-angle-deviation is greater than a predetermined deviation-threshold;

in accordance with the determination that the steering-angle-deviation is greater than the deviation-threshold determine a frequency of the steering-angle-deviation; and

activate the alert-device when the frequency of the steering-angle-deviation exceeds a change-threshold.

2. The warning system in accordance with claim 1 , wherein the curvature-detection-means is a digital-map that detects the curvature based on a location of the host-vehicle on the roadway.

3. The warning system in accordance with claim 1 , wherein the curvature-detection-means is a camera that detects the curvature based on lane-markings on the roadway.

4. The warning system in accordance with claim 1 , wherein the change-threshold is greater than three counts of occurrences of the steering-angle-deviation.

5. The warning system in accordance with claim 4 , wherein the change-threshold is exceeded in less than five-minutes of continuous drive-time.

6. The warning system in accordance with claim 1 , wherein the deviation-threshold is greater than 15-degrees of steering-angle.

7. The warning system in accordance with claim 1 , wherein the deviation-threshold is based on a speed of the host-vehicle.

8. The warning system in accordance with claim 7 , wherein the deviation-threshold is decreased when the speed of the host-vehicle is less than a dynamic speed-threshold.

9. A warning method, comprising:

indicating, with an angle-detector, a steering-angle of a hand-wheel of a host-vehicle;

detecting, with a curvature-detection-means, a curvature of a portion of a roadway traveled by the host-vehicle, said portion characterized as ahead of the host-vehicle in a current direction of travel;

alerting, with an alert-device, an operator of the host-vehicle;

determining an average-steering-angle, with a controller-circuit in communication with the angle-detector, the curvature-detection-means, and the alert-device, in accordance with the steering-angle indicated by the angle-detector;

determining an expected-steering-angle based on the curvature detected by the curvature-detection-means;

determining a steering-angle-deviation based on the average-steering-angle and the expected-steering-angle;

determining whether the steering-angle-deviation is greater than a predetermined deviation-threshold;

in accordance with the determination that the steering-angle-deviation is greater than the deviation-threshold;

determining a frequency of the steering-angle-deviation in accordance with the determination that the steering-angle-deviation is greater than the deviation-threshold; and

activating the alert-device when the frequency of the steering-angle-deviation exceeds a change-threshold.

10. The warning method in accordance with claim 9 , wherein the curvature-detection-means is a digital-map that detects the curvature based on a location of the host-vehicle on the roadway.

11. The warning method in accordance with claim 9 , wherein the curvature-detection-means is a camera that detects the curvature based on lane-markings on the roadway.

12. The warning method in accordance with claim 9 , wherein the change-threshold is greater than three counts of occurrences of the steering-angle-deviation.

13. The warning method in accordance with claim 12 , wherein the change-threshold is exceeded in less than five-minutes of continuous drive-time.

14. The warning method in accordance with claim 9 , wherein the deviation-threshold is greater than 15-degrees of steering-angle.

15. The warning method in accordance with claim 9 , wherein the deviation-threshold is based on a speed of the host-vehicle.

16. The warning method in accordance with claim 15 , wherein the deviation-threshold is decreased when the speed of the host-vehicle is less than a dynamic speed-threshold.

17. A warning system, comprising:

a means for detecting a steering-angle of a hand-wheel of a host-vehicle;

a means for detecting a curvature of a portion of a roadway traveled by the host-vehicle, said portion characterized as ahead of the host-vehicle;

a means for alerting an operator of the host-vehicle;

a means for determining an average-steering-angle in accordance with the steering-angle indicated by the means for detecting the steering-angle;

a means for determining an expected-steering-angle based on the curvature detected by the means for detecting the curvature;

a means for determining a steering-angle-deviation based on the average-steering-angle and the expected-steering-angle;

a means for determining whether the steering-angle-deviation is greater than a deviation-threshold;

a means for determining a frequency of the steering-angle-deviation in accordance with the determination that the steering-angle-deviation is greater than the deviation-threshold; and

a means for activating the means for alerting the operator when the frequency of the steering-angle-deviation exceeds a change-threshold indicative of driver-fatigue.