TMC Traffic Receiver Does the Job

Preface
This review is written based on this product's use on the Garmin Nuvi 360 GPS unit. The use of this product is isolated to the Washington DC area where I live. Details regarding use on other GPS products and locations will not be discussed.

Introduction
GTM12 is a traffic receiver for Garmin GPS products to allow the GPS to identify and optionally avoid areas where there is increased traffic. The information is obtained from Clear Channel's Total Traffic Network service which is a subscription based service costing about $60 per year limited to various specific locations in the US:

http://www.garmin.com/products/gtm11/coverage.jsp

Compatible Garmin GPS units can be found here along with company information:

http://www.garmin.com/products/gtm12/

Hardware
The antenna is basically a long wire with a mini-USB connector on one end. This end connects to the Nuvi 360 (and other compatible Garmin units) USB port. The antenna is active ONLY when there is an external power source, otherwise a warning message flashes stating antenna use has been deactivated. There are 2 suction cups that one can use to anchor the antenna to the windshield. The manual states that vertical orientation works best and the wire is only just long enough to connect to the unit and be oriented from the bottom to the top of the windshield.

Activation
The initial activation involves plugging the antenna in, being in an area where service is provided, and activating the service. Activation requires a few stepts:

First getting a code specific to the Garmin unit which one than writes down. This is accomplished by going to the toolbox menu on the Nuvi 360 and entering the traffic sub-menu. One than follows the step-by-step instruction provided at which point in the end, a code is shown.

Next, you need to enter the code on Garmin's website specific for this purpose at:

http://www.garmin.com/fmtraffic/

Follow the step-by-step instructions provided which ultimately ends in an subscription activation code.

Finally, one takes this activation code back to the Garmin unit and enters that code in where prompted.

Usage
It's pretty much plug-and-play once the subscription is activated. At least in the Washington DC area, the antenna starts working within the I495 beltway which is really too bad since traffic does extend out into the entire Northern Virginia area where I live and work. As soon as traffic info is received, the unit displays the various problematic areas as yield caution signs on the map. Various symbols represent different causes of traffic congestion:

Road Condition
Road Construction
Congestion
Accident
Incident
Information

By touching the yield sign on the GPS unit, a list of all the traffic information is listed along with severity. Severity is broken down into different color codes:

Green (low severity)
Yellow (medium severity)
Red (high severity)

How does the severity translate? Well, from personal experience, green is pretty mild where one is going essentially at the speed limit with occasional brake taps. Yellow is when one is averaging 10-20mph slower than the speed limit with multiple break taps. Red is bad and I usually wish I rode the bike instead.

Not only does it show areas of traffic with these yield signs, it also displays on the map the stretches of roads affected.

Conclusion
Why did I purchase the GTM12 over the others? Well, basically 2 reasons. I only had 2 options for the Nuvi 360 and this was the only one I could install myself. The other antenna, the GTM10, requires professional installation. The antenna itself seems to work fine. Clear Channel's traffic information is more or less accurate once taking into consideration that traffic is a dynamic state... Overall satisfaction with the service is probably C+. The antenna itself is an B-. Ideally, it would be nice to make the antenna less obtrusive.