After testing these units, two must-haves for us are live traffic updates (without a paid subscription) and the posted speed limit. The speed limit information is drawn from map data, and in our testing proved very accurate. It reflects changes on the same road, which we often miss and Roscoe P. Coltrane takes advantage of. The traffic feature identifies traffic delays on your route. It also gives an indication of how long the delay is-we found this to be very optimistic, but helpful nonetheless.