This interface should be implemented in order to receive traffic merge warnings. Note: The traffic merge warner is a point warner, which means that for a traffic merge there will always be 2 warnings emitted, with the TrafficMergeWarning.distance_type set to DistanceType.AHEAD and DistanceType.PASSED which is given when the location of the traffic merge is reached. A TrafficMergeWarning will not be given until the previous warning of that type has been passed. For example, a route with TrafficMergeWarning 120 meters and TrafficMergeWarning 160 meters ahead, the first TrafficMergeWarning.distance_to_traffic_merge_in_meters is 120 meters and the next TrafficMergeWarning.distance_to_traffic_merge_in_meters is then 40 meters, since that is the distance between the first and second warnings.