Assuming you live in a city that has all the sensors and cameras to see the traffic data. If you don't (which is the majority of the cities in the US) then you are at the mercy of those people who write the reports and push it out to the system. In most cities there are no magical automated systems on the roads that can see the accidents, road closures, etc. It is all typed into the system by a human. If they don't bother to enter the data then those with xm traffic won't get the reports.

 

Correcctttttt.

And just to clear things up for everyone else:

NAVTEQ Traffic utilizes all available data from departments of transportation, police and emergency services, government and private traffic sensors, cameras and airborne reports.

Accident reporting relies on human interaction for details such as location and severity as well as verification of reported incidents. The time span from when an accident occurs to when it is displayed on the navigation system will vary by time of the occurrence as well as location. Traffic icons may also remain on the navigation display for a period after the accident has cleared.

(From the XM FAQ)

 

oh, and how I want infiniti to support this: http://www.xmradio.com/weather/ground.xmc

:X

 

Funny you should mention this... I live in the DC metro area (Northern VA), and while I can see traffic information like congestion and accidents, I have been wondering why the hell the nav isn't suggesting alternate routes if it knows traffic is heavy on the route it calculated.

A short while ago, there was a tanker that spilled 5500 gallons of antifreeze or something on I-95 south and I'll be damned if the nav system didn't plot me a course right INTO the congo line.

I clicked through the settings and turned on everything I could and manually choose "detour" and manually set the range to 5 miles and then it came up with a detour that I was already thinking it should have.

Is this thing really supposed to AVOID heavy traffic or will it only re-route you if the road is closed OR only if you manually choose "detour" and set a distance?

I was really hoping that this was going to be more or less an auto-pilot scenario here, but it seems as though it isn't. I'm sure this area is heavily covered by XM Nav traffic since it's one of the top 3 or 4 congested areas in the country with a huge population to boot.