So today I saw something out of the ordinary... A speed sign that only turned on once you got about 15ft from it .. got my speed then shut off and displayed it... It was not a photo radar but wow very scary if stuff like this starts getting used everywhere. The redline gave me some alert time but only about 200yds there were cars passing it left and right to. So im guessing it was very low powered or very fast instant on trigger. It was k band btw.