imabell - I might be old fashioned but there is something comforting about being on primary radar and controlled by a well trained air trafficer. The prospect of having another screen in the cockpit and using it to try and achieve increased traffic density sounds like a recipe for disaster. If it is only going to be used as a glorified TCAS then use TCAS instead but if it is going to let sensible separation minima be reduced ('at pilots discretion' no doubt) then we will see a lot more mid-airs and airproxes.