So i was on the 5 in LA sitting in traffic in the 2000 TL-P i bought a few months ago, on my way to san diego. It wasnt ur basic move along bumper to bumper at 10 mph (if u live here u know what i mean), it was total dead stop. The navigation all of a suddenly says recalculating and has me get off the highway, take surface roads for about 3 miles, and get back on the 5, where it was now totally clear. Does anyone know if the navagation has some sort of traffic sensor for highways, maybe if theres a big accident it uses the radio signal that some stations send out, because ive been in many traffic jams while ive been driving here, but nothing has ever hapened like that before. I was seriously impressed and curious on how this system works

 

If you're on the interstate and come to a dead stop, the computer takes that as an indication of some sort of traffic problem. Simple.


I was traveling in a major road where speed limit is 50 and there was a big traffic jam. I was in my dad's Denali and the navigation system showed me a back road to the left, running parallel. I was like, sweet! Too bad I didn't get navigation on my car. Should've...

 

The 2nd generation navigation systems do not have any kind of input from external sources. Nor does the computer recognize a stop or crawl for an extended period of time as a traffic problem. The only way it will recalculate automatically is if it sees you (a) took a wrong turn, or (b) are no longer on a recognized road. Since the system uses dead reckoning more often than GPS queries for tracking, it's possible that a crawl can make it momentarily think you are not on a recognized road and recalculate. However, those are the only times it will do so. Unfortunately it is not that smart (yet).

 

Piano man-
Are you totally sure about that because it still told me to to exit the freeway, about 1/4 of a mile down the road at that. Additionally, dead reckoning is based on wheel speed and the gyro so it would not be any external source to let it know that you were stopped on a freeway.

 

Someone want to go out on I-15 or some other interstate at 3am and test this? :-)

 

Positive. The navi system only relies on the input from the driver regarding route choices (direct, easy, detour) and its pre-programmed mapping algorithms. Your sytem can detect when you're sitting still when a route is mapped because it is constantly calculating estimated time of arrival based on current speed and miles to travel. If you stop on the highway, the system ignores momentary stops in its calculations (red lights, etc). But if you suddenly stop in traffic or start crawling at 5 mph in a traffic jam, the system will eventually start recalculating the estimated time of arrival and you'll see the time remaining start to climb. It "knows" you're in a traffic jam only in the sense that your speed has slowed dramatically. As for it having you exit the highway, I can only speculate that for some reason the system thought you were no longer on the intended route and recalculated the route and figured that exiting the highway was faster at that point.