ETA / TTG

[Frits]

I drove yesterday a trip from +- 80 km.

TTG was estimated at 58 min.

While driving (most of them highway +- 60km) TTG was reduced by +- 20 min.

I drove at the right speed ( in Belgium 120/90/70/50 km/h).

When I see this differance in real and estimate TTG (+ 50%) then I wonder how navman can do an accurate routing (do they?).

[tcs17_tim]

I get this all the time, I think there is a gross assumption about speed which is a long way out on a 2 to 3 hour motorway journey.

[Frits]

Tested it again today .

Trip of 14 min. estimated at 20 min.

[gambitgander]

ETA's and TTG's are IMPOSSIBLE to calculate exactly, due to slowing traffic, road works, and a whole myriad of other unforeseen factors. As far as I can assertain, the TTG is calculated using only distance and road speeds, nothing else.
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Who's Your Daddy?

[Frits]

Ok but this morning 20/14 min. ther was no traffic jam no road works: a normal morning.

Also the trip of 80 km no traffic jam no road works.



I can accept of a estimated ttg that is shorter then te real trip but not 50 % longer.



Any idea what are the speed setting in navman?



You should also try tomtom2. Here you can adjust speedsettings. With this progam TTG is almost correct when there is no traffic jam or road works.

[tcs17_tim]

I find my 3 hour motorway journey at about 80mph is predicted as 4 hours but gradually falls until we are accurate at about 20 mins away.



I reckon they use about 60mph average, which is OK for single carriageway but not motorway.

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