I have bought the very high priced 3597 with HD traffic thinking the traffic info would be better than the standard traffic in the analogue models. Sadly, that's not the case. The Garmin subscription service as already mentioned is based on your cellphone's internet/data connection. When travelling outside your own country roaming data plans are very expensive so that is not a viable option for many. For within your country, I think you're much better served by subscribing to free twitter traffic feeds and free web based traffic cams then paying for a subscription or traffic service from Garmin. I now won't be bothered trying to get TTN on my 3597.