This is an old subject but it is pretty pathetic how XM Navtraffic flow in the Cayenne PCM doesn't show major highways here on Long Island. This is a high population area and of the 8 major highways, XM shows traffic for 3 of them. I got several XM representatives calling back after I called to see if it was truly that limited, they verified that they do not cover those major roadways.
Those with smartphones probably already access Google Maps which shows the traffic flow on countless roads. I like the way the traffic flow display looks in the PCM and having it there instead of a smartphone would be real nice.