Anyone know what speed the Nav uses to calculate time? Does it know the speed limits on each of the roads? With my Infiniti Nav, I can usually knock about 10min/h off of the time it tells me. Also, in Europe with the Euro Nav disk, does it just use the upper Autobahn speeds to calculate time? I'ave always been curious about this.
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My uneducated guess is that the average speed of any road section is coded on the DVD. How that average speed determined and its accuracy are probably Navteq's little secret.
At any rate I've noticed that the NAV is permanently adjusting the estimated arrival time based on how you're proceeding in reality. I.e. if you get stuck for 5 minutes in some traffic jam, it will add those 5 minutes to the estimate.
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I was wondering this also as we cruised for a couple of hours in Germany averaging 175kph and the nav destination time was always accurate. I guess it assumes you will be driving fast while in the no limit zones. In the US the arrival time is always accurate with 70mph speed limits. This is with a Nuvi 350
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It's pretty good for highway driving, but once you get into city streets with red lights and what not - it has no clue (naturally). At least that has been my experience, I would trust the highway part, and then add ~15 min for the city streets for example
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Quote: | Anyone know what speed the Nav uses to calculate time? Does it know the speed limits on each of the roads? With my Infiniti Nav, I can usually knock about 10min/h off of the time it tells me. Also, in Europe with the Euro Nav disk, does it just use the upper Autobahn speeds to calculate time? I'ave always been curious about this. | In my case it is something fictional because the only time it is accurate is at 4 a.m. And then, only until about 4:30 a.m. It hasn't heard about "traffic jams," slow speeds, or even speed limits on non-freeway streets. The ETA is essentially useless to me except to piss me off.
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How does the Nav calculate time to destination?