Estimated time of arrival

[imagoodfella77]

Has anyone else had trouble with this. My tt completely overestimates the ETA on all distinations. Not just by a little bit either, more like double. On a two hour trip the tt says it will take 4 hours 30 minutes. I live in Canada and so have set things to metric. But its almost like it's calculating the ETA based on miles and not kilometers. Is anyone experiancing the same or even have a solution.

That said I really have enjoyed this unit. I find that I really can personalize it. I did try a Garmin 650 and returned it to keep this unit.

 

[drewcfknight]

Is it possible you have it set to Walking Routes? I know it sounds dumb, but it happens to the best of us--okay fine...just me.

-Drew

 

[canderson]

Has anyone else had trouble with this. My tt completely overestimates the ETA on all distinations. Not just by a little bit either, more like double. On a two hour trip the tt says it will take 4 hours 30 minutes. I live in Canada and so have set things to metric. But its almost like it's calculating the ETA based on miles and not kilometers. Is anyone experiancing the same or even have a solution.

That said I really have enjoyed this unit. I find that I really can personalize it. I did try a Garmin 650 and returned it to keep this unit.

We've done a bit of work, and down here in the US (probably yours as well), it seems that our units use fixed assumptions about speeds based upon road type, not speeds specific to individual roads. You could be on the Bonneville Salt Flats and the most you'd ever get factored into an ETA is 60mph, same as you would on every rural interstate in the US even though our speed limits vary considerably from that.

Since we've done the exercise in mph, I'll leave it to you to tell us what you see in kph.

For each of the following road types, plot a fixed and straight course. Review the km and the time for each, divide, and give us your 720's kph:

Major divided highway, rural (max speed you'll ever do legally!) (about 60mph)
National highway, rural, not divided (about 40mph)
In town street (not designated with a highway number) (about 25mph)

 

[will381796]

We've done a bit of work, and down here in the US (probably yours as well), it seems that our units use fixed assumptions about speeds based upon road type, not speeds specific to individual roads. You could be on the Bonneville Salt Flats and the most you'd ever get factored into an ETA is 60mph, same as you would on every rural interstate in the US even though our speed limits vary considerably from that.

Since we've done the exercise in mph, I'll leave it to you to tell us what you see in kph.

For each of the following road types, plot a fixed and straight course. Review the km and the time for each, divide, and give us your 720's kph:

Major divided highway, rural (max speed you'll ever do legally!) (about 60mph)
National highway, rural, not divided (about 40mph)
In town street (not designated with a highway number) (about 25mph)

What's weird is that I set my TT 720 to run though a cross-nation trip in "Demo" mode and it shows a maximum speed on interstate highways as 75 MPH, which is actually pretty realistic for most people that drive on an interstate. It doesn't make sense that they would use one speed in "Demo" mode and then use a completely different speed to calculate ETA. I'm sure there's a pretty complex algorithm used by the TT software to calculate GPA and it probably takes into account traffic delays, stops for gas, etc that a person is likely to make along their route.

For in-city drives I find the ETA to be very accurate (within 5 minutes).

 

[twistrman]

What's weird is that I set my TT 720 to run though a cross-nation trip in "Demo" mode and it shows a maximum speed on interstate highways as 75 MPH, which is actually pretty realistic for most people that drive on an interstate. It doesn't make sense that they would use one speed in "Demo" mode and then use a completely different speed to calculate ETA. I'm sure there's a pretty complex algorithm used by the TT software to calculate GPA and it probably takes into account traffic delays, stops for gas, etc that a person is likely to make along their route.

For in-city drives I find the ETA to be very accurate (within 5 minutes).

the TT ETAs are insanely off. this is my biggest gripe with it, right next to odd routing from time to time.

mine is almost always 2 to 3 times the real length. i mapquested a bunch of different places and compared to the tomtom. most of them were that amount more and a few were close. i often had to choose alternate route once to get the same mapquest route as well.

so i think it's something wrong with the TT's firmware and algorithm's and all that. i did a like 4 mile trip between 2 houses i know, it's normally a 10 mintue trip, it said 35. on a trip between 2 state's i do often, it is a 5.25 hour trip, it says close to 7. so this is the thing i hate, yes HATE about the TT.

i have ran other trips on demo mode, sped it up to maximum amount, i think it's like 4 or 5 times the speed. and watched it. on major highways it would say 75, so i think that's very realistic, but on some roads that are 55, it would say it was going 41. so that makes no sense at all. ETA is often how i choose what route i want, so that's why i dislike that part so much. and i don't know if it's going to be 2x more 3x more, or like 5 minutes off, so i can't even do the division myself.

It's something they seriously need to fix. my dad has an older garmin, and it's is right on with the ETA. If they fixed this i could excuse it's bad routing sometime (although why they're at it, why not fix that too).

 

[twistrman]

back with another comment on this already. so i just pulled up google maps (which i pretty much trust, although i know nothing is perfect) and my TT.

planned a route from indiana to michigan, a route i know really well because for 2 months my wife and i lived in different states because of work, so we drove this a lot.

same exact routes were planned by them. mileage varied by about a mile but that's just because google doesn't know where i live (one this i love about the TT, only thing that can mind my apartment, google, mapquest, and garmin can't find it...) Estimated time for each of them, google:3hr 11min and TT: 3hr 22min. So that's not too bad it's close, but that's because this was almost all expressway. the TT does an alrgiht job estimated expressway use.

So then i hit the alternative route button on TT, and then went through it step by step and modified the google route. milage varries by 1 or 2 miles again, not a problem. time google:4hr 2min and TT: 4hr 57min. So, almost an hour off by not taking the expressways.

Also as google updated my route as i told it where to go and would calculate the reamaining area, it went a different way as the TT, and i had to force it to go the TT way, but i do believe google had a better route, but that's besides the point.

So when i have some spare time tonight, i'm going to make some burgers now, or i would do more, i'm going to test this with abunch of different places and see how far it is off. for different ways involving different roads.

 

[canderson]

So when i have some spare time tonight, i'm going to make some burgers now, or i would do more, i'm going to test this with abunch of different places and see how far it is off. for different ways involving different roads.

As a test, just take one stretch of rural interstate anywhere in the country. Plot a route on it long enough to make the division of miles/minutes work well enough (30+ miles or more). I think you'll find that even if you avoid towns altogether, you won't be able to get more than a 60mph average.