Arrival Times misleading

 

With the download to the 2010 maps it seems that my estimated time of arrival is predicated on driving slightly over the limit. With the 2008 maps, I usually picked up some time over the long haul as I generally travel 5-10% over limit. Now I seem to lose time over the long haul.

It would be great to be able to adjust the system to allow for my driving habits.

Anyone know how I can change the driving preferences as a percentage of posted speeds? It may be that the 2008 maps had older speeds but not sure. (Nuvi 360)

--
Tom

recent experience

I have not seen the 2010 maps, still using the last 2009 update. On a recent trip I observed that the arrival time seems to be based on driving at exactly the speed limit across the entire route. If I held to the limit, whatever it was in any given state or stretch of road, my ETA held steady. If I drove under the limit (traffic, road construction, weather conditions or so on) the ETA began to move towards a later time.

Of course, the device made no allowances for stopping for gas or food, after such a stop you simply had a new, later ETA. That makes sense to me.

What did surprise me was that the nuvi also seems to make no allowances for red lights. I drove through a major section of West Virginia that has perhaps a dozen red lights along it (US 19 north of Beckley). Each time that I had to stop for a light (or even slow down for one) I lost time from my ETA. If I were coding this and the data knew where the red lights were I would have allowed for some average delay at each light and factored it into the ETA. If you just caught the light and were stopped longer (or worse, if you had to wait for multiple cycles) then the ETA would move out, but if you caught the light when it was green then you would gain a little on the ETA. Over the long run things should average out. But the nivi does not allow for any delay at lights in it's ETA calculation, so the number is unrealistically optimistic. This same holds true for stops at toll booths, which can take a while if there are a few cars in front of you.

There is no way to adjust the nuvi calculation, at least not in my 250. You just learn to use it as a first estimate and factor in your knowledge of the route and expectations of road construction and your own driving habits. In my case it was off by about an hour for a 9 hour trip, with only a stop for gas and grabbing a burger to eat while driving at the same time.

I'd love to see seconds

I'd love to see seconds displayed in the ETA, just for fun, so you can watch them go backwards or forwards, depending on your speed.

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Nuvi260

Anyone comment on TomTom IQ Routes?

Are there any TomTom owners who could comment on the IQ Routes that TT advertises? The advertisements say that IQ takes into account historical speed and time of day. They go on to say that you will get a very different route at midnight vs during the day in cities with heavy traffic. But they're not really talking about just traffic avoidance.

Just wondering if it works in practice as well as it sounds. One would think that this would result in more accurate arrival time estimates, too.

Hmmm

Xmech2k wrote:

I'd love to see seconds displayed in the ETA, just for fun, so you can watch them go backwards or forwards, depending on your speed.

That would be interesting to see. Sometimes even when you speed up a bit it doesn't change the time. I was coming from PA to MD and was playing with the arrival time. It was interesting to see how much time you could shave off of a trip.

times

Yea, on a recent trip the wife commented on the arrival time and how accurate was it. So, I told her to watch and I slowed down for a minute and the time increased, and she was amazed at how it knew that. LOL

I've noticed that the Nuvi doesn't account for winding roads, or slower roads (typically under 50mph). Some recent driving showed that even going 40-45 (speedlimit) on some roads resulted in the arrival time increasing by a few minutes, but then driving 50+ on the same roads did not, or not enough for it to increase by minutes for me. And hte stop lights are true, they do not accommodate for traffic, stop lights, accidents, potty breaks, etc.

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Nuvi 660 owner.

Would that be another feature?

I was thinking you would have to add another choice in there like car,bike,ped. This one could be labled "Bladder" and could have levels like Trucker, Man Possesed, Normal, Woman, >6yo Daughter, Multiple Daughters! mrgreen

I am kidding!

Although the family will be driving to the Jersey coast in a month, myself the wife and the 6 year old and 1.5 year old. I forsee a lot of stops. smile

Now one feature that I would really like is the fuel feature from the Zumos, plus add the mileage function.

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Nuvi 3790LMT, Nuvi 760 Lifetime map, Lifetime NavTraffic, Garmin E-Trex Legend Just because "Everyone" drives badly does not mean you have to.

Time

rgroves wrote:

Yea, on a recent trip the wife commented on the arrival time and how accurate was it. So, I told her to watch and I slowed down for a minute and the time increased, and she was amazed at how it knew that. LOL

I've noticed that the Nuvi doesn't account for winding roads, or slower roads (typically under 50mph). Some recent driving showed that even going 40-45 (speedlimit) on some roads resulted in the arrival time increasing by a few minutes, but then driving 50+ on the same roads did not, or not enough for it to increase by minutes for me. And hte stop lights are true, they do not accommodate for traffic, stop lights, accidents, potty breaks, etc.

Way back when, I used to teach my Rescue workers and Firefighters in driving class that a 10 mph increase in speed over a 10 mile drive will only decrease the travel time by 1 minute.

In my observations of the GPS ETA, slow downs do make a difference in ETA in a short time, because they are usually significant changes below the AVERAGE speeds. Going faster results in a slower ETA change response, because you have to get signifcantly above the AVERAGE speed for the road type for a pretty good length of time to make the ETA change.

Just remember, the GPS figures ETA and travel time by the AVERAGE speed for the road types, not actual speed limits.

As and example, next time you take a long trip, take note of the time you leave and the time you arrive, barring any overnights stops, and divide that time into the miles traveled. I'd be willing to bet that unless you hit the Interstate and drove sustained speeds without stopping, you would be hard pressed to get much over a 50 mph average.

I drove from Denver, CO to my homw in VA in one straight stretch. I stopped only for fuel, (I had a cooler for food). Even driving at sustained speeds 8 mph over posted limits, I was only able to average 62 mph.

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Frank Nuvi 3597LMT 37.322760, -79.511267

yes it uses the actual speed limits

phranc wrote:

Just remember, the GPS figures ETA and travel time by the AVERAGE speed for the road types, not actual speed limits.

I don't believe this is correct. Do you have a source for your "information", or is it just your opnion?

I don't believe it because I saw exactly the opposite on the road. I was on Interstate highway through several states for most of my trip. The states had different speed limits by state for the Interstate highways, basically the same type road. If I did 65 on a stretch of Interstate marked 65, my ETA did not change. If I did 65 on Interstate where the limit was marked as 75, my ETA grew. What kept the ETA from growing was driving at whatever the posted limit was (not allowing for reduced speed limits in work zones), not some overall average.

Look at it another way. If you go 70 in a 65 mile zone, and maintain that long enough (without stopping to discuss it with an officer), your ETA slowly and slightly improves. If you go that same 70 in a 75 mile zone your ETA drifts backward. There is no way that this supports a claim that the gps ETA isn't based on actual speed limits as the nuvi understands them.

My nuvi does not have the speed limit display feature. But some do and apparently that information is in the map database. It is not at all unrealistic to think that the nuvi is using that speed limit by each segment of road to calculate ETA. It seems unreasonable to say that it isn't, based on observation.

ETA countdown

Xmech2k wrote:

I'd love to see seconds displayed in the ETA, just for fun, so you can watch them go backwards or forwards, depending on your speed.

I know this works on the 265w.
While enroute, tap the top "next turn" bar to get to the turn list. On that screen click "Show map". On the bottom right of the map screen is an ETA countdown in hours:mins:secs till arrival. On the bottom middle is a distance countdown.
Not quite the ETA arrival time, but a countdown with seconds nonetheless.

You can

Xmech2k wrote:

I'd love to see seconds displayed in the ETA, just for fun, so you can watch them go backwards or forwards, depending on your speed.

if is is less than a 1 hour trip

tap the green bar and go to the list of turns and such and then the last one is destination and it will show the time in min & sec there.

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Garmin nuvi 2455LMT (wife uses nuvi 255w) (sold C330)

I said

The Average for the road type. The Garmin knows what the speed limit is in each state and adjusts it accordingly.

I also have about a million miles under my belt using GPS. I know what I speak about.

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Frank Nuvi 3597LMT 37.322760, -79.511267

I concur.

phranc wrote:

The Average for the road type. The Garmin knows what the speed limit is in each state and adjusts it accordingly.

I also have about a million miles under my belt using GPS. I know what I speak about.

From my observations, some research, and accumulated knowledge - the arrival time is calculated based on a formula that takes into account the speed limits on the route, and an average speed for the road type, as well as individual's driving habits by taking into account deviations from the averages on a particular route

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*Keith* MacBook Pro *wifi iPad(2012) w/BadElf GPS & iPhone6 + Navigon*

Hmm

I find that my arrival time gets adjusted if I drive over the limit or change my route. The time is always correct when I arrive at my destination. I like to see the minutes get shaved off when I drive 10 mph over the posted limit (freeways). It also adjusts when traffic delays are present and are removed or when stopped at a light or are in heavy traffic.

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JRoz -- DriveSmart 55 & Traffic

Seconds

That would be great! It would almost make getting somewhere into a game. Lose some seconds here, go faster and make up some seconds there. Maybe they could even integrate it into a game!

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southland

Just My Observation...

On my frequent 120 mile drives between St. George, UT and Las Vegas, NV, the speed limit is 75. I gain about 5 minutes on my Nuvi ETA by driving between 70 and 75, which leads me to believe that the Nuvi utilizes a " standard" (65mph)?) rather than the posted speed limit in its calculations

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- Hugh -

I Agree

phranc wrote:

The Average for the road type. The Garmin knows what the speed limit is in each state and adjusts it accordingly.

I also have about a million miles under my belt using GPS. I know what I speak about.

i have experienced the same, but not nearly as many miles as phranc.

--
No matter where you are "Life is Worth Living".

Great comments but not to my point. help - please!

I travelled 7 hours mostly highway over the weekend. I wrote the time I started, the ETA by the Garmin. While I stopped enroute, i kept the Garmin on. Stopped time agreed with my watch. My over all average was 8% HIGHER than the limit of the higheays travelled. My actual arrival time, after deducting stopped time was IDENTICAL to the original ETA. My actual time should've been 8% less than the ETA - but it wasn't.....why?

--
Tom

Seconds

Xmech2k wrote:

I'd love to see seconds displayed in the ETA, just for fun, so you can watch them go backwards or forwards, depending on your speed.

I'd like to see seconds included in the regular time, let alone the ETA.

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

ETA

kch50428 wrote:
phranc wrote:

The Average for the road type. The Garmin knows what the speed limit is in each state and adjusts it accordingly.

I also have about a million miles under my belt using GPS. I know what I speak about.

From my observations, some research, and accumulated knowledge - the arrival time is calculated based on a formula that takes into account the speed limits on the route, and an average speed for the road type, as well as individual's driving habits by taking into account deviations from the averages on a particular route

I think you may be crediting the navigator with too much 'intelligence' (per se).

I suspect it just adds up the time required to cross each link in the present route.

A link is a section of road between two nav points which have common attributes based on that link's length and the link's speed limit (among other factors). Each map is made up of millions of links. As you traverse each link I believe it adjusts the ETA based on the remaining time to cross all of the links left to cross, PLUS the time to reach the end of the current link based on the speed limit.

They MAY have amended the travel time in the mapping based on historical speed data for road sections or in the navigators, based on driving habits, but I don't work for Garmin and I don't work in Cartography so I have no idea how they've implemented it (though I have been associated with the AVL industry since 1986).

Nothing would prevent them from projecting ETA based on your rate of speed relative to the speed limit over the current link or even over the entire route, but I just don't think it is all that 'smart' about it.

I just don't believe that they've done it.

And nothing would prevent them from keeping ongoing stats to tailor the ETA values based on your historical propensity to speed (or go slow for that matter). Obviously some reasonability would have to be applied to the calculation, because if you always go 10 over and it is factored as a ratio, driving 40 in a 30 over long periods would push the unit to project you to drive at an average of 80 in a 60.

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

ETA

birchtree wrote:

I travelled 7 hours mostly highway over the weekend. I wrote the time I started, the ETA by the Garmin. While I stopped enroute, i kept the Garmin on. Stopped time agreed with my watch. My over all average was 8% HIGHER than the limit of the higheays travelled. My actual arrival time, after deducting stopped time was IDENTICAL to the original ETA. My actual time should've been 8% less than the ETA - but it wasn't.....why?

Were you using the navigator's speedo or were you using the car's? Car speedometers can be optimistic, some by a pretty fair margin.

Or, as has been suggested, Garmin may have adjusted the ETA values based on historical speeds over the highways in question.

In other words, your navigator may have EXPECTED you to go 8% over the limit.

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

~

bramfrank wrote:

I think you may be crediting the navigator with too much 'intelligence' (per se).

I suspect it just adds up the time required to cross each link in the present route.

It does exactly that... and also takes into account your deviations from the expected norm and calculates an arrival time for the present route.

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*Keith* MacBook Pro *wifi iPad(2012) w/BadElf GPS & iPhone6 + Navigon*

ETA

kch50428 wrote:

It does exactly that... and also takes into account your deviations from the expected norm and calculates an arrival time for the present route.

Route? Or link?

And, if the route, do they project based on absolutes (10 over) or percentages (perhaps in the case of starting out by travelling 40 in a 30, projected over a trip that then takes you for hundreds of miles on the interstate, for example)?

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

ETA Calculation

The Garmin device and method calculates estimated time en route and estimated time of arrival if you input a plurality of variables, including identity, cartographic data, final destination. Upon receiving the inputs, the GPS determines from cartographic data the estimated distance to the final destination and the type of thoroughfare the inputted trip will traverse. During operation, the GPS will recall the average driving velocity for the inputted driver over each different type of thoroughfare traversed. Using prestored average velocity data, the Garmin GPS calculates an initial estimated time en route and an estimated time of arrival for a desired route. The device continues to receive GPS data as to the driver's position and velocity and updates the average velocity record for that driver on the specific type of thoroughfare. As the average velocity fluctuates, the device adjusts the estimated time en route and the estimated time of arrival. The GPS further has control processes for potentially erroneous sampling. The GPS has a predetermined threshold in which data inputs below that threshold will not be averaged into the memory. The second control process of the present invention allows for zero velocity sampling without necessitating a reset of the entire system. If the GPS samples a zero speed, it will not average that velocity into the system as explained above. Rather, a stop time measured by a counter will be added to the estimated time en route and estimated time to arrival.

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Garmin Nuvi 260W Garmin Nuvi 1490T If you think knowledge is expensive, try ignorance.

Search

kch50428 wrote:
bramfrank wrote:

I think you may be crediting the navigator with too much 'intelligence' (per se).

I suspect it just adds up the time required to cross each link in the present route.

It does exactly that... and also takes into account your deviations from the expected norm and calculates an arrival time for the present route.

If you will do a search of this forum, you will find that the newer models do have adaptive routing. It does learn YOUR driving speeds on particular roads as well as the routes you tend to use. I know the 7x0 units do, and there should be others.

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Frank Nuvi 3597LMT 37.322760, -79.511267

ETA

MY driving speeds?

What about my wife? My sons? My daughter? All of whom drive my car.

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

It doesn't know who is

It doesn't know who is driving, but it will average out all the driving styles.

I think that one should use the GPS as a tool, and routes and ETAs are merely suggestions and estimates. The ETA is an ESTIMATED time of arrival, not a dead line.

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Frank Nuvi 3597LMT 37.322760, -79.511267

ETA

Can anyone point me toward any Garmin documentation on the topic? I'd be interested in reading up on it.

I love statstics.

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

Here is some info on the

Here is some info on the subject. http://www.gpsreview.net/train-your-nuvi-eta/

--
Charlie. Nuvi 265 WT and Nuvi 2597 LMT. Android Here WeGo - Offline Maps & GPS.

I agree

phranc wrote:

It doesn't know who is driving, but it will average out all the driving styles.

I think that one should use the GPS as a tool, and routes and ETAs are merely suggestions and estimates. The ETA is an ESTIMATED time of arrival, not a dead line.

From my Army days, ETA = "Estimate Time of Arrival",no more, no less. Some here are trying to make it a science project.

I fine that my 750 is always on the ETA time or very close to either, no matter what traffic or lights I hit.

--
Nuvi 50LM Nuvi 2555LM

ETA

frainc wrote:
phranc wrote:

It doesn't know who is driving, but it will average out all the driving styles.

I think that one should use the GPS as a tool, and routes and ETAs are merely suggestions and estimates. The ETA is an ESTIMATED time of arrival, not a dead line.

From my Army days, ETA = "Estimate Time of Arrival",no more, no less. Some here are trying to make it a science project.

I fine that my 750 is always on the ETA time or very close to either, no matter what traffic or lights I hit.

No one making it a science project here. Its not complicated as you thought. Its just not as simple as using the distance speed travelling to get the time.It uses a bit more usefull variables. Its not like an plane ride in the sky with little or no impediments

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Garmin Nuvi 260W Garmin Nuvi 1490T If you think knowledge is expensive, try ignorance.

IQ Routes Work

johnc wrote:

Are there any TomTom owners who could comment on the IQ Routes that TT advertises? The advertisements say that IQ takes into account historical speed and time of day. They go on to say that you will get a very different route at midnight vs during the day in cities with heavy traffic. But they're not really talking about just traffic avoidance.

Just wondering if it works in practice as well as it sounds. One would think that this would result in more accurate arrival time estimates, too.

I've had my GO 930 for almost one year now, and have been very satisfied with the routings and ETAs. The accuracy depends upon how much feedback TomTom has had on the route. Around the Dalls/Fort Worth area, from the first estimate to the actual arrival it is usually good to within five minutes (assuming there are no unusual traffic dealys like an accident or really bad weather). On some routes, where apparently there is more data, I have seen the initial estimate good to within two minutes. However, since it is constantly recalculating the ETA, it is almost always within two minutes as I get near the destination. I suspect some of this is due to not having actual speed limits for the smaller roads, and under estimating (say using 25 or 30 mph instead of 35 or 40 mph).

On longer trips (say 500 miles), I generally don't compare the initial estimate to my actual arrival time because I know I will be making several stops of varying duration. That said, once I start from my last rest stop and head toward my destination, I have found it to be good within five minutes, and good to within two minutes as I get closer.

There are times when it is right on the money, but variations due to stop lights and traffic make that more difficult.

--
Shooter N32 39 W97 25 VIA 1535TM, Lexus built-in, TomTom Go

Average is average

phranc wrote:

It doesn't know who is driving, but it will average out all the driving styles.

I think that one should use the GPS as a tool, and routes and ETAs are merely suggestions and estimates. The ETA is an ESTIMATED time of arrival, not a dead line.

Since the GPS adjusts it's ETA by your driving habits, this helps in the original ETA. If you have many drivers, you could do a factory reset prior to your trip, then it should go by the speed limits. However, this is only one factor that contributes to your actual arrival time. The GPS does not take into consideration stop signs, traffic lights, or other traffic delays in the original ETA calculation. However, I believe that at any point in the trip, it has "forgotten" the earlier portion of the trip and recalculated your ETA from current position.

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Garmin StreetPilot c530, Mapsource

A Bet

I'll say this, no matter how fast or slow you drive, no matter how many times you stop, or for how long you stop, when you arrive at your destination, I'll bet a weeks pay that the ETA time will exactly match the time on the menu screen, Any takers?

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Frank Nuvi 3597LMT 37.322760, -79.511267

IQ Routes Use Historical Traffic Data

mkahn wrote:

The GPS does not take into consideration stop signs, traffic lights, or other traffic delays in the original ETA calculation.

I believe the point of TomTom's IQ routes is to take into consideration HISTORICAL traffic delays (submitted by users who chose to participate every time they connect their GO to TomTom Home) due to stops signs, traffic flow & etc. That is why you will get a different ETA for different times of the day. With the TomTom units using IQ routes, if you are planning a route, not just "Navigating to...", you can select a specific day of the week and time of day and get a different ETA based upon historical traffic patterns.

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Shooter N32 39 W97 25 VIA 1535TM, Lexus built-in, TomTom Go

I'll Take That Bet!

phranc wrote:

I'll say this, no matter how fast or slow you drive, no matter how many times you stop, or for how long you stop, when you arrive at your destination, I'll bet a weeks pay that the ETA time will exactly match the time on the menu screen, Any takers?

Pick me, pick me! grin Sometimes my ETA will be one minute off when I get to my destination. I suppose it is due to rounding (it does not show seconds).

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Shooter N32 39 W97 25 VIA 1535TM, Lexus built-in, TomTom Go

Well then, you should slow

Well then, you should slow up a half a minute to allow for that.

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Frank Nuvi 3597LMT 37.322760, -79.511267

Time of Arrival

I usually add 9 minutes to my time of arrival--due to traffic and red lights.

Arrival Times - ETA?

This is great information and very much appreciated. In my youth I competed internationally in car rallies and thus I'm really interested in the ETA calcs versus the ATA (Actual time of Arrival). Interestingly, since I updated the maps and software, my ETA AT THE START OF THE TRIP, always matches my ATA within 1 or 2 minutes after deducting stops enroute.

Yes I'm fully aware that the ETA will always be correct when I ARRIVE, what's interesting is that it is now correct when I LEAVE/START! Adaptive learning is a great answer...wonder if I can adjust so that the ETA will include my bio stops......fun to get it right as I enjoy calling frineds two provinces away and saying I'll be there at x and arrive precisely at x.

--
Tom

ETA / ATA

Great discussion... how do I change the learnings.....leave unit on when I stop for instance?

--
Tom

Here is Some info on the

charlesd45 wrote:

Here is some info on the subject. http://www.gpsreview.net/train-your-nuvi-eta/

Great link. Thank you

--
Tom