It happens me quite often, that when riding in a city, cars folowing me are not detected. I search for cause and find out, that when cars comming from side road and not exceed my speed by 5(or 7mph) are not detected. I know that something similar is mentioned in manual, but did not realize that its not limited for cyclist or low speed, but only for speed difference. Its then common that big fast moving cars follows me and are not detected. I tried that with my friend, who was comming from side road and following me in big Q7, driving close behind me and driving fast - up to 50mph downhill and varia was unable to detect that. It is very unpleasant, because it is quite common situation and it lowers usefulness of Varia Radar device, it definitely should be fixed, I am loosing my trust in Varia Radar detection and it doesnt improve my traffic awareness.
if it bothers you, send please feature request on www.garmin.com/ideas or www.garmin.co.uk/support
Its only way, because I think that Garmin doesnt read this forum