The Obstacle Collision Avoidance System - OCAS - is an obstruction marking and warning system using advanced 3D radar technology. OCAS provides both visual and audible (optional) warnings to aircraft on potential collision course towards obstructions such as wind turbines, power lines or communication towers. OCAS improves flight safety and the environmental profile of obstructions by eliminating light pollution. OCAS can be integrated with all known obstruction lights and has central automated operation and supervision with 24/7 service.