Systems and methods for alerting to traffic proximity in the airport environment. Knowledge of the geographic position, speed, rate of change of speed, heading (or track-angle) and/or altitude of own-aircraft (or vehicle) and another, potentially conflicting aircraft (or vehicle) are used to calculate a predicted distance between the two aircraft (or vehicles) at given point of time in the future. If separation distance is predicted to be less than a predetermined acceptable value, then an alert message (aural, visual or both) is issued to the pilot or operator of the vehicle.