Fast is not always faster

Actually it usually CAN factor in the lower speed limits and more stops on a 2-lane road.

It can NOT, however, factor in you driving a LOT over the posted speed limit on the freeway.....or a little over for a long way. Think that might have been a factor ??

I'll leave it for the Garmin users to address "forcing" a route but the other way is to use your EYES and follow the road signs.

Then there is the obligatory......are you sure it is set for "fastest"?

Ignoring the GPS for a moment, be very very careful while driving on local highways southwest of Jacksonville. The area is renowned for speed traps and the local specialty is a sudden drop in speed limit on a four lane highway where you don't expect it and the lone sign is easy to miss. The cop will be watching for immediate ticketing.

Certainly highway driving is likely to be more consistent, barring any huge delays due to construction or accidents. What I've found with my TomTom and with Google Maps is that they usually suggest a "Fastest Route" that mostly sticks to the major highways. However, when I choose the "Avoid Freeways" alternate route the estimated time is often just a couple of minutes longer (e.g., only 5 or 6 minutes on a 3-hour trip) and the distance is considerably shorter. In that case I usually take those routes because the major highways are so boring.

It's the same route as the Garmin.

As far as I can tell, going to Tampa is quite a detour. I'd have to agree with ka1167 that the higher speeds are probably what made the trip 'quicker'.

Try it at the speed limit next time and see...

The GPS knows the speeds for each road and can calculate for that but it doesn't know how many red lights that you may pass along the way.
I have found the "fastest route" still is the best choice for me.

I think you have that exactly backwards.

All the reports I have seen indicate that the mapping indeed DOES know about stop signs and traffic lights BUT........there is no way for it to know AHEAD OF TIME what speed you are actually going to drive.

You are more likely to exceed the speed limit by a significant amount on an Interstate than on a two lane road.

The speed for each road shows on the screen by a speed icon. That speed is embedded into the map. If your unit has traffic, you will see that speed icon. The GPS uses this to calculate the fastest route. And yes, the unit will not know how fast you intend to drive that route.
The unit does not know where or how many red lights that exist as they are not a part of any map.

Also, I have found that when on a divided highway, it doesn't know about each left-hand-turn that exists thru the median. That's why sometimes it tells you to go past your destination (if it is on the left) and has you make a "U turn" ahead and come back to your destination.
I think there are others here that will verify all this.

I live in southeastern PA and my wife's parents live in northeastern PA, with my Garmin set for the "fastest" route it takes almost all interstate type roads, set the same destination for the "shortest" and it takes a more direct route through lots of small towns about halfway into the route.

The "shorter" route is about a half hour quicker in total time, and a good bit shorter in milage.

Doesn't make sence but that's the deal.

I simulated driving to the post office. It blew through all 3 stops signs at 30 MPH.
And the speed limit on side streets in my town is 25, but that info is not on the 1490 so it calculates at 30.

Garmin seems to have no concept of stopping at stop lights, ETA is apparently based on the assumption that you never get to one when it is red. And I've often seen Garmin pick a longer or slower route when my GPS was set to shortest/fastest respectively. So the best advice is to use common sense, and go the way that you expect to work out the best for your driving style, you might be smarter than a few ounces of electronics.

It would be interesting to see Garmin put a feature on the GPS for routing; give simultaneous routing on the 'Go' screen for fastest, shortest, ECO route etc.

Then let the chips fall where they may, and let the user decide.

And you know that exactly HOW ??
Just because it doesn't show that information doesn't necessarily mean that it isn't there.

The map certainly knows how many intersections that there are along a given route. If it doesn't know specifically which ones have traffic control devices, it should be using some kind of algorithm (average) to gestimate how many there are along the way and what impact it likely will have on your average speed.

Then again, after reading some subsequent posts, maybe I give the programmers WAY too much credit. I must admit that I've never really paid close enough attention to the ETA to see if it looks reasonable or not on a non-Interstate route.

Traffic data is only available near BIG cities.....and I quite assure you that it is NOT available for most of the route(s) that started this discussion, if any at all.

So, it's all a bunch of guess work, and none of us has access to enough real information to actually know exactly how it works.

The estimate for an Interstate should be more accurate, if you follow the speed limit, because there are fewer variables to contend with.

Which all just goes to prove that a consumer grade GPS device is just a "crutch" and like a real crutch, is no substitute for walking on your own two healthy legs !!

GPS' are just more convenient crutches, that's all. However, in heavy traffic, in a new place, it's a God-send for the lost and confused!

That would include me.

I agree with what you have said, however..

On many interstate trips I tend to drive a bit spiritedly, and my initial ETA has consistently been within 5 minutes of my actual arrival time. This has happened quite a few times on 300-500+ mile trips. When I was traveling at 70 MPH, my ETA will actually increase if I maintain this speed for a period of time.

When I first got the unit, my ETA estimate was well over, but after a few trips it seems to predict my arrival quite well.
Now, if I stop for a redlight, then the ETA will increase depending on how long I stop.

Shrifty wrote:

Are you speeding at 70? Does the prediction keep changing to a sooner time, or later time?

Are you saying that your unit remembers how you drove the route last time? My 1490 does not.

I agree with this statement.

All my Garmin GPSs have been 'right on the button' as far as the arrival time reflected on the screen. Upon arrival at my destination, the reflected arrival time is ALWAYS correct. Never once has it been incorrect.

[Think about that for a moment.]

Gary Hayman
Garmin Tricks & Tips
http://bit.ly/garmin_gps_tricks

But then the end point according to the unit was incorrect and further up the road.

Highest speed limit around here is 65, and the ETA keeps getting pushed back to a later time at 70MPH. This includes driving in a 55 zone as well. As for the question am I speeding, I will plead the 5th

When set to 'fastest', if I am driving down Interstate 66W in Virginia, my Nuvi wants me to leave the interstate, drive through a town with multiple stop lights, and then re-enter I66 5 miles down the road.

So where it would take me 5 minutes to get there if I stayed on the interstate, it takes 25 minutes to go through the town.

If it is set to 'shortest', it stays on the interstate.

Who knows why.

I'm making a quick assumption that you are refering to US29 near Centreville. Without traffic lights, it is possible that this route could be faster (not by much though) if you were able to maintain your speed. It would be nice if Garmin took traffic lights into consideration when calculating ETA.

The weird thing is the shortest route should also be 29 for this period as it is straighter and more direct of a route.

I've noticed this before. I went to Niagara Falls last summer and it was telling me to go a way that Google Maps didn't. I took the Google way, and it immediate dropped 35 minutes off of my ETA. So obviously it wasn't the fastest route (since it was 35 minutes longer) and it wasn't the shortest route either.

This is why I have a tendency to look at Google Maps first instead of just relying on my (albeit old) SP550.

the computer brain has its limits, your own fastest way will always be more logical

Of course

But at least I know with the GPS that I will get there. Left to my own devices or paper maps I am iffy at best

I now see the humor in my typo there, and need to clarify

I was refering to the INITIAL ETA that was given, just prior to starting a trip and comparing that to my ACTUAL ETA.

On a recent 400+ mile non-stop trip from CT to Western PA (almost 100% Interstate), the INITIAL ETA was within 3 minutes of my ACTUAL ETA, and my speed did not drop below 75MPH (traffic was light).

It seems that the GPS would have to be able to predict or estimate the speed at which you will travel in order for the INITIAL ETA to be that accurate. If it had relied on the speed limits, then the INITIAL ETA would have been off by about an hour or so.

This is strange considering I'm using a c340.

Have I not read here somewhere our GPS's do keep track of our actual speeds?

When I put in faster, my GPS always takes highways no matter if it takes me out of my direct route. When I put in direct, it takes side roads.

I always refer to Google maps before any long trips and do a simulation on the GPS for the exact same route. If the Google directions are better, I just simply download that route to the GPS.

I know that when I first set up my TomTom it asked me if it could collect the travel times I encountered and relay them back to TomTom as input for their IQRoutes feature. However, I don't think that individual GPS units "learn" the driving habits of their users and adjust the link times.

You may be thinking of this ... http://www.gpsreview.net/train-your-nuvi-eta/

I'm convinced their routing algorithm doesn't consider all roads. Sometimes it will try to get me off the highway and take some local roads. When I ignore it, and stay on my route, it then re-calculates and five minutes disappears from the arrival time. In this case, it clearly knows that my route is faster, but for some reason, didn't consider it.

The 3760 does better than my old 350, though. The 350 would often try to put me on a local-access highway with lots of red-lights, when the interstate is at least 5-10 minutes faster.

I think the real issue here is that solving the problem is very computationally intense. Even with perfect information such as 100% accurate traffic reports everywhere and redlight coding, it has to take some shortcuts, somehwere. There's no point in taking 15 minutes to calculate a better route that saves you 2 minutes.

Bottom line - if there's a better route available, take it. If not, then you're none the wiser!

You guys don't remember the thread from a year or so back that the Garmin units actually remember your habits. The average speeds you drive as opposed to the actual speed limits, and uses this as a factor when determining the ETA. This was confirmed by Garmin, also.

I know that my 760 has remembered my average speeds from using it on my school bus everyday for months at a time. Anytime I use it for a real trip, the ETAs are way off, due to me only averaging 30-35mph for days and days on end. Sometimes it's so far off, I have to do a reset on it to start anew.

Thanks for the reminder, I'll have to look it up. This would make a lot of sense on my unit, as I've programmed the same route into my sister's c340 sitting a foot apart (same software/map/firmware) and they showed completely different ETAs.

http://www.gpsreview.net/train-your-nuvi-eta/

That's interesting. I didn't consider the option of just noting that the user tends to drive x% above the limit... or something like 20 km/h over the limit on the highway, 10 km/h over the limit on arterial roads, etc.....

It makes sense though. There - I learned something today.

Thanks for the reminder. I was fairly certain that others had determined that our Garmin units were using data based on our particular habits over the time since a hard reset (if any).

I have had my GPS route me out of the way on interstates, which was more miles and slower - it'll get you there, and if you are not familar with the area, it works - but local knowledge is not programable.

My 2460LMT does the same thing on one of my routes back home. It chooses what *appears* to be the fastest route, but if you happen to hit the first light, you're screwed. That light stays red forever.

I guess that's not taken into account in their calculation.

Exactly what phranc states.

https://support.garmin.com/support/searchSupport/case.faces?caseId={c499adc0-9bb3-11dd-e87e-000000000000}

I programmed a destination, first fastest then shortest. I performed a hard reset then repeated both ways. Now my Nuvi predicts a quicker ETA on the shortest route via back roads, & remains about the same on the fastest route via the interstate.

value you get after initial route calc is just that. No way will the GPS know about the length of stop lights, etc. that's why your eta always changes enroute.

Yes, they do. They also keep track of a lot of the other things you do, and many companies use/sell that data to their "marketing partners."

I'd suggest reading your GPS manufacturer's Privacy Policy, you might be quite surprised...

I don't so much mind that they do this, but I feel VERY strongly that I should have the right to opt out and not share my personal information with them without my knowing about and expressly agreeing to it.

NP

but that won't work...my 765T will just recalculate the imported route, UNLESS you force a route with waypoints

I have noticed when I slow down, the ETA will change to a later time. It will also change to earlier time if I drive faster than speed limit.

My guess is, the GPS is recalculate the ETA all the time if the average speed is changed.

Last time I looked, my Garmin GPS doesn't transmit anything to anybody. Has your tin foil slipped?

My Magellan doesn't either....as it has no WIFI capability and never gets connected to the Internet.

Anyone who does "Web Updates" however, can never be sure what might be transmitted.

Here is the privacy statement http://www8.garmin.com/privacy/

Note in particular this sentence:

"This Policy does not address our practices regarding information that we collect through our products or applications, when you register a product on my.Garmin.com, or when you interact with our support personnel."

This is Garmin's Privacy Policy relative to the information they collect and store about us through their software and devices: http://www.garmin.com/garmin/cms/site/products/home/products...

NP