A method of activating the use of a low-definition map by a driver assistance system of an autonomous vehicle, said low-definition map being assessed for reliability, said autonomous vehicle traveling on a road and comprising a navigation system and a perception system, the navigation system comprising said map and providing mapped data, the perception system providing measured data of the autonomous vehicle and/or the external environment of the autonomous vehicle, said method being updated periodically when said autonomous vehicle is traveling on a road and comprising the steps of:
- receiving data mapped by the navigation system, the mapped data comprising at least a mapped slope of the road around the autonomous vehicle, at least one mapped curvature of the road around the autonomous vehicle, and a mapped list comprising a list of mapped road signs, the mapped list further comprising, for each road sign, a location and contextual information;
- receiving data measured by the perception system, the perception data comprising a measured slope of the road around the autonomous vehicle, a measured path of the road around the autonomous vehicle, and a measured list comprising a list of road signs measured, the measured list further comprising, for each road sign, a type, a location, and contextual information;
- determining a mapped path of the road from the mapped curvature;
- calculating a road correlation value from the at least one mapped slope, the mapped path, the measured slope, and the measured path, such that the closer the match between the mapped data and the measured data, the greater the correlation value is;
- calculating a sign correlation value from the list of mapped road signs and the measured road sign list, such that the closer the match between the mapped data and the measured data, the greater the correlation value is;
- determining a reliability indicator, wherein the reliability indicator is determined, from the road correlation value and the sign correlation value, on at least 4 levels:
- a first level indicating good reliability of a current speed limit, good reliability of a past speed limit, and good reliability of the road geometry, said first level defined by the sign correlation value being greater than a first threshold and the road correlation value being greater than a second threshold;
- a second level indicating good reliability of the past speed limit, good reliability of the road geometry, and insufficient reliability of the current speed limit, said second level defined by the sign correlation value being greater than a third threshold, said third threshold being less than said first threshold, and the road correlation value being greater than the second threshold;
- a third level indicating good reliability of the road geometry, insufficient reliability of the current speed limit, and insufficient reliability of the past speed limit, said third level defined by the sign correlation value being less than the third threshold and the road correlation value being greater than a second threshold;
- a fourth level indicating insufficient reliability of the current speed limit, insufficient reliability of the past speed limit, and insufficient reliability of the road geometry, said fourth level defined by the sign correlation value being less than the third threshold and the road correlation value being less than the second threshold;
- activating the use of low-definition map by the autonomous driving system if said reliability indicator is determined to be at said first level.