Estimated Arrival Times - How are they calculated?

metroace

When I had a ViaMichelin, one could enter the speeds you estimated you drove at on various road types and it used those to calculate an estimated time of arrival for any planned journey.

How does the TomTom ONE calulate an estimated time of arrival?
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TomTom XL Europe
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Andy_P · Posted: Sun May 27, 2007 9:55 pm Post subject:

Old TomTom Navigator software had a similar function, but by the time the hardware models arrived, they'd removed it. They still use the same method, but don't give the user the chance to customise it.
I've never seen the actual figures they use published, but looking at what speeds are used when it performs a "Demo Route" would probably give you a good idea.

Oldboy · Posted: Sun May 27, 2007 10:01 pm Post subject:

The TT uses a similar method, only different in that you can't attach your own speeds to a particular road.

Each segment of road, from one junction to the next, has a time tag allocated to it.

The software just aggregates all the time segments of the Route left to travel.
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Richard

TT 910 V7.903: Europe Map v1045
TT Via 135 App 12.075: Europe Map v1120

DennisN · Posted: Sun May 27, 2007 10:11 pm Post subject:

I once tried to get at this by setting a route entirely along a motorway and seeing what the distance and time turned out to be, then dividing or somesuch sums to get average speed. A conveniently easy result would have been the same minutes as miles, but that's not my luck!! I had the idea of doing this with several routes. But I simply couldn't be bothered (or face the maths - sums isn't one of my strengths).
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Dennis

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Noman · Occasional Visitor Joined: May 15, 2007 Posts: 8

Would be interesting to now. As it works now its totally useless. A typical 1 hour drive holding the speed limits on non motorways calculates appr 1:30

Oldboy · Posted: Sun May 27, 2007 10:51 pm Post subject:

It used to be that a 70mph road was calculated to about 62mph. Presumably to allow for holdups. Laughing

Problem is, if they get the actual speed of the road wrong, (several posts on this in the Forums) this will change the perceived time of travel, which will make a nonsense of the ETA.

Having said that, in most of the long journeys that I've made in the UK, the ETA seems to be over estimated by 10%. Not a bad thing to arrive early. Smile

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Richard

TT 910 V7.903: Europe Map v1045
TT Via 135 App 12.075: Europe Map v1120

DennisN · Posted: Sun May 27, 2007 11:13 pm Post subject:

Robin2 · Posted: Mon May 28, 2007 12:39 am Post subject:

My experience is that on motorways I can't gain on TomTom, even when driving at the limit for extended periods on quiet motorways. However, when I come off the motorway, I travel considerably faster than TomTom predicts, particularly on single carriageway A roads. My feeling is that TomTom uses something like 40mph on single carriageway A roads but nearly 70mph on motorways
A journey I do quite often is from Peterborough to Swansea. On the first part, A14 (dual), M6, M42, M5, M50 my ETA stays almost constant, but when I leave the A449 and take the A465 the ETA comes down visibly
Robin
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metroace · Posted: Mon May 28, 2007 8:53 am Post subject:

Thanks for all your replies.

I'll be taking my first motorway journey with TT today. Just a quick run out to Reading to take Mrs M to Costco. That journey is mostly motorway.

After that, we may head out in the Hare Hatch direction to have a spot of lunch somewhere. That will be totally off motorways.

After that, I'll get a hang of the ETA situation in relation to my own driving style.

Edited once for typos - metroace
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TomDavison · Posted: Mon May 28, 2007 9:48 am Post subject:

I use the limited speed option, and set it at 60mph. On non-motorway routes, there is little if any difference from fastest. When long motorway routes are involved, the limited speed is more accurate.

Set to fastest for a journey, I did about 20 miles along a motorway, at 70mph on the satnav, using cruise control, and my arrival time at the end had extended by a minute. Clearly, the motorway cruise speed is assumed to be just over 70mph.

Daggers · Posted: Mon May 28, 2007 10:28 am Post subject:

DennisN · Posted: Mon May 28, 2007 10:44 am Post subject:

metroace · Posted: Mon May 28, 2007 10:55 am Post subject:

Calm down, calm down! Laughing

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TomTom XL Europe
Apple iPhone 3GS

TomDavison · Posted: Mon May 28, 2007 11:16 am Post subject:

Just done a route demo on motorways, and it's driving at a steady 69mph. Looks like my cruise control isn't absolutely accurate, but there's no way you can average 69 on our motorways without exceeding 70.

sweepdog · Occasional Visitor Joined: Mar 14, 2007 Posts: 51

Are you guys saying that the speed limit info on non motorway roads has now been removed on TomTom GO maps? Before I updated my maps, I used to get a very accurate represenation on the A roads (eg when it changes from 40 to 50), but now I only get 70 on motorways

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