An apparatus comprising at least one processor and at least one memory (60, 62) including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least perform: identify each of a plurality of paths through an intersection from map data; identify signal phase and timing data for each traffic light associated with each path through the intersection; receive probe data for vehicles approaching or traversing the intersection; estimate a number of vehicles in a queue, to traverse the intersection along a path of the plurality of paths through the intersection, during a red phase of a traffic light controlling the path through the intersection, based on the signal phase and timing data and the probe data by map-matching at least a portion of the probe data received for the path through the intersection and estimating a number of vehicles in the queue, to traverse the intersection along the path through the intersection, during a red phase of the traffic light controlling the path through the intersection; identify a green phase of the traffic light controlling the path through the intersection, based on the signal phase and timing data, wherein the green phase of the traffic light is subsequent to the red phase of the traffic light; estimate a number of vehicles of the vehicles queued, during a next red phase of the traffic light subsequent to the green phase of the traffic light, that failed to traverse the intersection during the green phase of the traffic light, based on the signal phase and timing data and the probe data; estimate a congestion status of the path through the intersection based on the number of vehicles that failed to traverse the intersection during the green phase of the traffic light; and cause the congestion status to be provided to permit updating of a map, to reflect the congestion status, for use by a navigation system. identify each of a plurality of paths through an intersection from map data; identify signal phase and timing data for each traffic light associated with each path through the intersection; receive probe data for vehicles approaching or traversing the intersection; estimate a number of vehicles in a queue, to traverse the intersection along a path of the plurality of paths through the intersection, during a red phase of a traffic light controlling the path through the intersection, based on the signal phase and timing data and the probe data by map-matching at least a portion of the probe data received for the path through the intersection and estimating a number of vehicles in the queue, to traverse the intersection along the path through the intersection, during a red phase of the traffic light controlling the path through the intersection; identify a green phase of the traffic light controlling the path through the intersection, based on the signal phase and timing data, wherein the green phase of the traffic light is subsequent to the red phase of the traffic light; estimate a number of vehicles of the vehicles queued, during a next red phase of the traffic light subsequent to the green phase of the traffic light, that failed to traverse the intersection during the green phase of the traffic light, based on the signal phase and timing data and the probe data; estimate a congestion status of the path through the intersection based on the number of vehicles that failed to traverse the intersection during the green phase of the traffic light; and cause the congestion status to be provided to permit updating of a map, to reflect the congestion status, for use by a navigation system.