Technology Review – XM’s NavTraffic

By Kevin Gordon


At 5:04pm on Friday you start your car to embark on your trip home. You have spent the last three hours watching the clock, waiting for the school bell to release you. Once you finally escape the confines of your office, the last thing you want is to be snarled traffic, doubling the time of your commute. As you glance at your navigation screen, you see your typical route home peppered in yellow triangles connected by red lines. Your future has been predicted, and you are screwed. Or are you?

This is often the quandary you are presented with if you have up-to-the minute information on what traffic is doing ahead of you. In this instance, the dilemma presented by a navigation system that has the ability to gather and present traffic data. For the past two years, I have had the chance to live with one of the better implementations of these systems, in a 2007 Acura RDX.

During those two years I have seen red (a bad sign for traffic flow) on almost a daily basis. Initially, when my navigation system would alert me to slow moving traffic ahead, I would avoid the highway in question. Instead, I would jump on my favorite back road, and smugly assume that everyone else was stuck suffering in bumper-to-bumper traffic. The thing I learned as time passed? More often than not, I was better off heading for red and waiting through it, as I had before I was enlightened by technology.

Before I go too far in this story, allow me to lay some foundation. I live in the Philadelphia area. On a daily basis, I drive on the busiest road in Pennsylvania, which is rarely anything but a 15-mile-long parking lot. This is especially true on a Friday night. When I started shopping for my most recent car, I decided that I had to have navigation. Once I found out that I could receive live traffic updates overlaid on top of the map, I added that feature to my ‘must have’ category.

There are a number of players in the traffic information market, and it is a matrix of technologies, services, and information gathering. To start, a number of services gather and disseminate traffic information. For the purposes of this review, I’ll stick to the three largest services; NavTeq, Inrix, and Total Traffic. In addition there are five ways for receivers to gather traffic information. Information flows from Satellites, FM radio transmitters, Cellular towers, car-to-car, and over the internet (most likely over cell towers). Please note; the newest stand alone systems, like the Dash Express are starting to explore car-to-car, cellular, and Internet information delivery. The others are coming down from above or over the airwaves with your FM signal. The ways the three service providers capture information are similar, and comes from a variety of sources. These sources include (but are not limited to): commercial traffic services, road sensors, traffic cameras, historical information, and emergency services. So we have three services, five ways of delivering information, and five ways to gather traffic information. This is getting a little complex, so let’s focus on the system in the car that I chose.

In Acura’s RDX, traffic information is provided by XM’s NavTraffic service. This service is available on a large number of cars and trucks from Acura, Cadillac, Chevy, Infiniti, Lexus, Nissan, and even the 2009 Porsche Cayenne. In addition, you can buy aftermarket navigation systems from Alpine, Garmin, and Pioneer that have the capability to subscribe to the service. The XM NavTraffic Service is sold as an additional subscription charge on top of a standard satellite radio subscription, or as a stand alone service at a higher cost. XM delivers the service from their satellites, and it is received by the same XM antenna that acquires XM radio.

So does it work? It depends on your definition of working. And in the next few paragraphs, I plan to further hedge my bets! Unfortunately, a few conditions and rules apply to determine your potential success.

First, you need to allow a freshly-started car a few minutes (5-8) to pull down fresh information from the satellites. Any information you see on your screen instantly is most likely historical data flow information. While useful, it is giving you the average speed on a road for a particular time, on a particular day. This rule partially applies to how close you are to the traffic in question. I have found that while taking long trips through an area that has coverage, (for example, driving past Washington, DC) you need to get reasonably close to the roads in question before making an informed decision on which route to take.

Second, you need to know your traffic symbols. Traffic flow covered roads are one of three colors. Green is free flowing traffic, in theory, 45MPH average speed or higher. Yellow is mild congestion, again, in theory, 25MPH-45MPH. Finally, red is heavy congestion or anything less than 25MPH. Realize that an average speed of 25MPH or even 20MPH might seem slow, but in comparison to smaller side roads with traffic lights and stop signs, it will get you to your destination as well as any secret route you may know. The real magic is the traffic alerts and symbols. When you see that red road ahead, make sure you scan for alerts, (shown as yellow triangles in Acura’s RDX) and make sure you take the time to read them. They are very good about stating that a lane is blocked or that an accident has just been cleared.

Finally, and most importantly, you have to live in an area with traffic coverage, and not just traffic incident coverage, but traffic flow coverage. Just because you live near a city that has it, does not mean that you are good to go. Make sure that roads you frequently travel are covered by service. I cannot stress this enough, shelling out the extra cash for the system or service is worthless if you spend less than 10% of your time in an area that has detailed coverage.

So does it work? For me, in a word, yes. I have a few minutes of driving before I hit a major route on my daily commute. I live in a well covered area. Finally, I have had enough experience to know when to stay the course and when to look for an alternative route. The NavTraffic services has saved me hours, if not days, in the past two years. Those times that you know more about what is ahead than the rest of the drivers on the road can be priceless.

My final thought would be that this technology is only going to improve, and being an early adopter comes with minimal penalty. The future is flowing green for traffic information incorporated into navigation systems.

Stay tuned for future review of some of the competing technologies detailed here. 

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Author: Kevin Gordon

Kevin is Autosavant's owner and Editor-in-Chief, responsible for setting the overall strategy and editorial direction of Autosavant. He's also the primary contributor to Autosavant's YouTube channel ( where you can find a comprehensive library of new-car reviews.

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  1. I hope then the XM’s NavTraffic won’t have some “glitches” then the GPS had when some tourists in Rio de Janeiro in Brazil, followed the direction in their GPS and ended in one of the less safest area of the city.

    Speaking of NavTraffic, GPS and to a latter extent, StreetView, there a good rant about StreetView at

  2. Stéphane, I can attest to the fact that XM’s NavTraffic has no ability to weigh the quality of an area before routing you through it. I can’t imagine the amount of problems with the political correctness police it someone attempted to build in some type of logic to do so.

  3. Thanks for the review–I purchased the Nav traffic for my Acura as it seemed a good value. I simply want it for traffic incidents –for example when I95 on the way to the Phila airport is congested more than usual. And I want traffic alerts; the roads I travel are major ones. Thanks again.

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