How Does the TT1 LE Calculate ETA?

[lateknightucd]

So I just had a weird experience when using my TT1 LE for the first time. I was driving down to my father in law's hunting camp and figured I'd give TT a little workout. Everything seemed to function well, but I noticed that the ETA and time remaining in the trip was always a lot later than I expected. On the drive home I realized that TT seems to be calculating the ETA based on driving 30 MPH regardless of how fast I'm going or how fast the speed limit is. Anyone have any ideas? For instance, I was doing 75 MPH on the freeway (speed limit of 70) with about 20 miles left on the trip and it said I had 40 minutes left. This error was consistent throughout the trip in both directions regardless of speed and/or speed limit. Thoughts? Thanks so much!!

 

[adagio]

That's the one thing I don't like about my unit. It almost always estimates way too long. I just expect it and adjust in my head accordingly. I haven't seen any solution so far. I keep hoping one of the new updates will allow it to be adjusted.

 

[lateknightucd]

Kind of disappointing, but so far I like everything else about it. Doesn't seen like it should be that hard to just average your speeds on freeways/highways/residential roads and then use that average accordingly to calculate ETA's based on your driving habits. Oh well...maybe in the next update.

 

[Three3]

Purely a guess (an educated guess?), but TomTom appears to know speed limits, or at least it's able to describe roads by some sort of speed category. This is what allows it to calculate "fastest routes," to sound speeding alarms if you've enabled that feature, and to calculate your initial ETA before you've even started driving. So, my theory is that this is all that goes into its ETA calculation. How many miles of what kind of roads remain between you and your destination, and how long would it take if you drove them at the speed limits. I don't think it factors your current speed into the equation.

Only a guess.

 

[lateknightucd]

Purely a guess (an educated guess?), but TomTom appears to know speed limits, or at least it's able to describe roads by some sort of speed category. This is what allows it to calculate "fastest routes," to sound speeding alarms if you've enabled that feature, and to calculate your initial ETA before you've even started driving. So, my theory is that this is all that goes into its ETA calculation. How many miles of what kind of roads remain between you and your destination, and how long would it take if you drove them at the speed limits. I don't think it factors your current speed into the equation.

Only a guess.

I considered this also, but the ETA seemed to be calculated based on a speed of 30 MPH both on the second half of way to hunting camp (mostly 45 MPH county roads) and on the second half of the way home (70 MPH) freeways...so I'm not sure that it really is taking speed limit into account.

 

[Pedro2NR]

Maybe this thread may help
http://tomtomforums.com/showthread.php?t=3052&highlight=arrival+time