A method is disclosed that includes, for a set of passages of a vehicle, where each passage is associated with at least one confidence level, applying at least one heuristic to confidence levels corresponding to the set to determine at least one score. The method also includes performing the applying at least one heuristic for a number of sets of passages of a number of vehicles and selecting a number of the sets based on their associated at least one scores. The method additionally includes outputting identifications corresponding to each of the selected sets. Apparatus and computer readable media are also disclosed.