I have a 3590 and that option is not available but noticed that it is available if I reset the unit and then select a European country. My problem with that was that the speed limit sign changes from the rectangular one like we have in the US to the round one they use in Europe and other countries I think.
I would have lived with that but there is no way to set the warning to other than one mph or kph over the speed limit. I usually drive 3-5 miles over the limit and would like the alert to sound at 6 mph over but there is no way to do that.
Of course, your model may not have it at all but if it does I hope this helped