XPost: rec.arts.sf.written, rec.arts.sf.science   
   From: jclarkeusenet@cox.net   
      
   In article , gossg@gossg.org says...   
   >   
   > Doc O'Leary  wrote:   
   >   
   > >Probably.  Many mapping apps have traffic congestion overlays.  The   
   > >sooner you can get them that information, the better.  The real problem,   
   > >like I said, is when you wait to give it to them until it is so late   
   > >that they feel inclined to do something stupid in reaction to it.   
   >   
   > My wife has a fairly recent GPS in her car.  Once, we had programmed   
   > the destination into the unit because we needed it for the final   
   > navigation -- we knew the way for the first fifteen miles.  But, with   
   > very little warning, it abruptly told us to take an exit three miles   
   > before the obvious one, and adjusted the time-to-destination   
   > accordingly.  As we turned onto the overpass, we saw traffic backing   
   > up from something further down the road.  At other times, it's given   
   > us a "congestion ahead" warning without changing the routing.   
   >   
   > How is traffic information sent to GPS units?  Is it sent via the same   
   > satellites?  Other satellites (ex XM)?  Via the cell networks?   
      
   Most common is FM sideband from local broadcast transmitters.  However   
   it may go by the cell network, HD radio, or other means.  The major   
   provider is a company called "Inrix" .   
      
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