The GTM 20 is an integrated FM TMC (Traffic Message Channel) traffic receiver, antenna and cigarette lighter adapter. Designed exclusively for the American version of compatible Garmin products, it receives digital information (where available) on traffic and road construction tie-ups that your compatible Garmin unit uses to offer an alternate route. TMC data, available in a fast-growing number of cities throughout North America, gives prompt, accurate notification of accidents, road construction, police, or emergency action, etc. — so you can visually monitor traffic flow and, if necessary, avoid traffic tie-ups.