I've tweaked mine to 73 mph on the highway, 46 mph on main streets/highways, and 37 on city streets. For my general area of travel, these provide very accurate estimates of my actual drive times. No doubt, your results will vary depending on your area and congestion on the roads you drive as well as the time of day you travel.utah said:If you have NAV, and you've set a destination, it will give you an ETA based on the average speeds you've got set in your nav options. I haven't really tested it though to see how accurate it is.