This site uses cookies to offer you a better browsing experience. Find out more about how to manage cookies, or dismiss this message and continue to use cookies.

Why does the Nuvi keep trying to take me on back roads?

1568101116

Comments

  • the 760 and 765T both work basically the same. I do like the 765T better as you have lane assist and traffic alerts. Tho we do get "Heavy Traffic Ahead" alerts while setting in the garage. Either one works... basically. But don't depend on either one for correct routing.

    There now is that clear as mud?

    Thats about what Garmin tech support says when they can't really answer your questions.
  • Boyd 1998 Points
    Does resetting the nuvi clear the favorites? I have lots of them that I do not want to loose.
    Not really sure about this, but even without resetting your unit, if you don't want to lose your favorites then you'd better back them up. Connect the Nuvi to your computer and locate the file Current.gpx on the Nuvi. Should be someplace like \Garmin\GPX\Current.gpx. Copy that file to your computer and your favorites will be backed up.

    If you need to restore them, or move them to a different Nuvi, rename the file temp.gpx and drop it into the same folder. Restart the Nuvi and they should be added to the favorites.
  • gatorguy 326 Points
    Yes, doing a hard reset will dump your favorites. And Boyd's solution for it is correct.
  • aslg 0 Points
    edited November 2009
    Finding the faster route has a lot to do with congestion.

    True, which is what live traffic receivers are for. Otherwise,
    "[a] vehicle would normally expect to achieve as an average" applies which in determining classification will take into consideration lights, lanes, etc.
    I am starting thinking that Garmin's classification of certain roads is wrong (too optimistic). We are talking here about millions and millions of road segments (segments because you can have different speed limits on the same road).

    How does Garmin acquire the information to compute the classification?

    We know that TomTom uses the real speed average for each specific road stored in the device and aggregates the results from all the users that allow Tom Tom to retrieve this data. The aggregation is not per road class, it is per specific segment and per time of the day.
    THIS IS GOOD, REALISTIC DATA.

    I followed Marc's recommendation and ran the simulator over the Austin-Corpus Christi route. On the small roads my speed was always +- 2 mph compared to the speed limit.

    Is that possible that when Garmin does not have realistic speed average of certain road segments, it bases the classification on the speed limit, when available, otherwise on the road type?
  • Tim 1482 Points
    Is that possible that when Garmin does not have realistic speed average of certain road segments, and it bases the classification on the speed limit, when available, otherwise on the road type?
    Absolutely.
  • I would just like to throw in my 2 cents worth.

    It seems to me that Garmin and other GPS makers should offer an option whereby someone can specify "fastest route" but also direct "major highway preference." Such an option would not take someone off a major highway just to save a few minutes of time. This way if someone really is willing to take a 2 lane back road that can save 5 minutes they wouldn't select the highway preference.

    If they really want to get sophisticated, I suppose they could ask for a percentage such as "Stay with major highways unless the time saving is more than xx% or perhaps xx minutes." I think this would solve most of these issues.
  • Tim 1482 Points
    There are still a couple of models that do that-- but that was also a feature on older Garmin StreetPilot devices. In the push for fewer settings to cater to more mass market users many of those customizations have dropped.
  • aslg 0 Points
    Is that possible that when Garmin does not have realistic speed average of certain road segments, it bases the classification on the speed limit, when available, otherwise on the road type?

    Absolutely.
    Another idea...
    I was intrigued by the fact that some users complain that older devices works better than newer ones. Others that older maps work better than new ones.

    Was the coverage of speed limits across all the roads 100% from, let's say, 2006 or does garmin increase coverage at each map revision?

    Let's consider this scenario: a small road does not have speed limit, it's classification based on road type is low. When compared to a highway in the proximity, it will lose. Everyone is happy :)
    At a certain map revision, the speed limit is added to that small road and its classification is increased. Now, in certain cases, that small road could win against the highway.

    The problem here is that using speed limits as a surrogate for average speed for small roads can lead to very wrong conclusions!
  • Tim 1482 Points
    Was the coverage of speed limits across all the roads 100% from, let's say, 2006 or does garmin increase coverage at each map revision?
    A few years ago there wasn't any speed limit data in the Garmin devices. That has increased quite a bit in the last couple of years in the Navteq data. What you describe is certainly plausible as a cause-- but difficult to prove.
  • aslg 0 Points
    edited November 2009
    I would just like to throw in my 2 cents worth.

    It seems to me that Garmin and other GPS makers should offer an option whereby someone can specify "fastest route" but also direct "major highway preference." Such an option would not take someone off a major highway just to save a few minutes of time. This way if someone really is willing to take a 2 lane back road that can save 5 minutes they wouldn't select the highway preference.

    If they really want to get sophisticated, I suppose they could ask for a percentage such as "Stay with major highways unless the time saving is more than xx% or perhaps xx minutes." I think this would solve most of these issues.
    Best of all would be using the TomTom IQRoutes mechanism to increase the accuracy of the average speed of the roads. Even better would be adding the time variable for the selection of the average speed.
    But maybe there are TomTom patents that could be infringed...

    I hope Garmin will understand that using speed limits as a surrogate for average speed is a bad decision but my expectation is low considering it did not do anything about this issue for at least two years.

    I like your pragmatical solution based on flexible preferences. If the data used for influencing the routing decisions is bad and nothing can be done to make it better, Garmin should give the user the capability to change the weight of that data.
  • gatorguy 326 Points
    The equivalent of TomTom's IQR on TeleAtlas mapping would be Traffic Patterns on Navteq. Some devices using NAVTEQ'S maps have begun offering it. I suspect Garmin soon will be too.
  • Tim 1482 Points
    Something else to keep in mind is that Navteq does have a product called "Traffic Patterns" which is essentially the same technology as IQ Routes. Tele Atlas has been gathering data for a longer time and thus has more data than Navteq Traffic patterns-- but the data is available for Garmin to purchase. To my knowledge there is just one GPS using Navteq Traffic Patterns data in the Magellan line... it might be interesting to see what it picks for the same route.

    But I'd also caution that while this explanation of speed limits/classifications is plausible, it could be something else entirely so we shouldn't expect that Navteq Traffic Patterns is the answer. (Although it would certainly be welcome in the Garmin lineup.) Perhaps Garmin doesn't think the amount of data Navteq has collected so far is worth the additional data cost.
  • I still would like to know why my *OLD* SP 2610 does an almost perfect route every time?

    It's a Garmin. Why would technology go backwards???



    bob
  • aslg 0 Points
    The equivalent of TomTom's IQR on TeleAtlas mapping would be Traffic Patterns on Navteq. Some devices using NAVTEQ'S maps have begun offering it. I suspect Garmin soon will be too.
    Do you think this will require new garmin devices or it will come with new map updates?
  • aslg 0 Points
    I still would like to know why my *OLD* SP 2610 does an almost perfect route every time?

    It's a Garmin. Why would technology go backwards???

    bob
    Do you have speed limits in the maps of your old SP 2160? Maybe the speed limits screwed up the routing decision for the routes that you take.
  • I still would like to know why my *OLD* SP 2610 does an almost perfect route every time?

    It's a Garmin. Why would technology go backwards???

    bob

    Do you have speed limits in the maps of your old SP 2160? Maybe the speed limits screwed up the routing decision for the routes that you take.

    I don't know wht you men by speed limits but the 2610 had advanced routing options with a variable slider for highway/med/slow roads (have to check wording)

    I left it on default, equal weighting for all 3 and fastest route always seems to be best.

    I just remembered that the 2610 had a "good/better/best" route preference and oddly, me and friends and Family that all own this unit found better worked better than best!


    bob
  • There are still a couple of models that do that-- but that was also a feature on older Garmin StreetPilot devices. In the push for fewer settings to cater to more mass market users many of those customizations have dropped.

    My Magellan 1475T has a "mostly" freeway setting that does what it says.

    bob
  • Boyd 1998 Points
    Ah yes, I really liked the routing preferences on my old 2620. But them days is gone forever....

    image
  • aslg 0 Points
    Ah yes, I really liked the routing preferences on my old 2620. But them days is gone forever....

    image
    FANTASTIC!
    I would fire the designer that decided to get rid of this flexible weighting interface and hire the designer of this interface back.
    Is this too complex for the average user? Use the avoidance settings in the primary dialog and show the complex settings only when pushing on the "Advanced" button.
  • aslg 0 Points
    Ah yes, I really liked the routing preferences on my old 2620. But them days is gone forever....

    image
    Now I am getting curious :)
    What settings are available in the Guidance, Time and Safety tabs?
  • Boyd 1998 Points
    It's been a long time... the safety tab lets you lock out most of the GPS functions when the vehicle is moving. The time tab lets you set the time. I guess guidance had something to do with spoken directions. Basically, this screen is like the settings menu on the Nuvi.
  • My question seem pertinent to this discussion. I haven't yet noticed any sort of route preview mode in my wife's new Garmin 265WT. (I just assumed that route preview was a standard feature since it is on most TomToms.) The way I feel about this is if it is going to take me on goofy "shortcuts" I want to be able to preview this in advance so I san set a wayby to get around the shortcut.

    If there is a preview, where do I find it?
  • SergZak 340 Points
    @JeepLover

    After you've selected your route's destination and hit the Go! button, press the green status bar at the top of the map screen. You'll be presented with a turns list. If you press the Show Map button, you'll be able to see the entire route on the map screen where you can also zoom in and scroll to inspect the route in more detail.
  • gatorguy 326 Points
    I could use an assist from a couple members please.

    Do any of the posters in this thread have a bonafide problem route, one that the error is repeatable for others with the same model device? Not looking for one where you simply disagree with the route or think some other way may be faster. What I would love is one where you've been routed off an Interstate ramp only to be put right back on within an exit or two, which would be a very obvious problem.
  • Marc 301 Points

    I hope Garmin will understand that using speed limits as a surrogate for average speed is a bad decision but my expectation is low considering it did not do anything about this issue for at least two years.

    I think you have to be careful about what you are assuming. I find the Garmin ETAs overly optimistic because they are assuming you are travelling well above the speed limit on certain roads. This is with a new GPS that has not learned my driving speeds. On a road where the speed limit is 45 mph, when I simulate the the route, it shows a speed of 52 mph. In fact I often drive this road during commuting hours, and the the true speed is more like 40 mph. During off peak hours 52 may be closer to average, but at no time do I see my device assume speeds close to the speed limit on this particular section of road.
  • xjack 0 Points
    We are losing focus here! this discussion is not about traffic lights or eta or other things - its primarily about bad routing options! Like the title says - "Why does the Nuvi keep trying to take me on back roads?"
    Ofcourse no doubt all the discussions about the details of navigation and calculations are interesting - but lets focus on the real issue - bad/ridiculous route selection by Nuvi.
  • gatorguy 326 Points
    One of the reasons I asked for the help of some of our members two posts back :)
  • Marc 301 Points
    I don't think we are losing focus. Somebody hypothesized that the reason for bad routes is that Garmin is using speed limits for average speed on a road when determing routes. I said I think that is a bad assumption.
    I do agree with gator that people that are yelling about bad routing should take him up on his offer of collecting bad routes so he can do something constructive with them.
  • xjack 0 Points
    Ok, I see how this discussion has progressed. I havent used my Nuvi for a while now. The last time was a couple of months back, I was travelling from Camarillo, CA to SFO. I checked the route on Google and saw that it was a simple straight road - US 101 N - no diversions, no exits...nothing! Just keep going on straight north and there is SFO.

    (So although there was no need for a GPS on this trip i wanted to play around with it so i turned it on)

    For me after I hit 101 it told me to take some exit after 15-20 mins on road...and i was thinking google map did not say anything about it...but eventually i decided to go ahead with Nuvi's directions....and i was lost in some small town there!!!! (i dont recall any names now). So i stopped at a gas station and asked or directions to 101...and on the whole trip every other exit it was telling me to take some exit!!!

    The other route to SFO is taking I-5 N....I am not sure if my Nuvi was forcing me to take I-5 N by routing me on those smaller back roads (I am trying to be optismistic)

    So anyways a normal trip which should take about 6-6.5 hours took me around 8...and all that extra time was spent driving on the narrow back roads.

    I also stopped my car a couple of times inbetween and changed the settings from fastest route to shorest route to eco drive and it still kept telling to take those exits. I am sure there are no other shorter routes there.

    If you tell me i did something wrong or missed something then i would love it and will definetly work on it...but untill then i would still maintain Nuvi has bad routing.

    The only thing i missed doing before my trip was to stimulate the route on the gps... i found it very tedious (maybe i dont know how to do it correctly)

    Anyways this was my experience with it...hope it helps in any way.

    Mine is Nuvi 1200.
  • gatorguy 326 Points
    Unfortunately, without route specifics such as start and end, map version, app version and model, there's nothing that others can try on their devices to see if they get the same results, and thus it's not very helpful. If you have that and can share it then that's the type of route info I need.
  • I don't find any of these problems in the UK. I rarely get routed off of major motorways/trunk roads.

    Could well be related to Navteq map data in the USA.
  • aslg 0 Points

    I hope Garmin will understand that using speed limits as a surrogate for average speed is a bad decision but my expectation is low considering it did not do anything about this issue for at least two years.



    I think you have to be careful about what you are assuming. I find the Garmin ETAs overly optimistic because they are assuming you are travelling well above the speed limit on certain roads. This is with a new GPS that has not learned my driving speeds. On a road where the speed limit is 45 mph, when I simulate the the route, it shows a speed of 52 mph. In fact I often drive this road during commuting hours, and the the true speed is more like 40 mph. During off peak hours 52 may be closer to average, but at no time do I see my device assume speeds close to the speed limit on this particular section of road.
    You reasoning is flawed because Garmin does not use ETA and driving learning for the calculation of the route. It uses road types and average speeds (some of them wrong because based on speed limits) hard coded in the maps. This, of course, creates another issue: even if your driving habit is to drive on highways at 200 mph, and at 5 mph on minor roads, (these are purposely exaggerated to make the point clear) Garmin will still select the route with minor roads :)
  • Marc 301 Points
    So you are telling me that the 52 mph I observe on a new GPS running in simulation mode in not the average speed it assumes. Why should I assume it is the speed limit, as you say? My point is you made an assumption that average speeds are around the the speed limit based on running the simulator. I have shown you a counter example where average speed was not around the speed limit. I make no further claims about how it's routing, only that your assumption may not be true. Yes this also results in inaccurate ETAs in this case, but I am not linking them as cause and effect. I am not claiming I know why in some cases it picks minor roads and in others it does not. I do not think we have sufficient information for that.
  • aslg 0 Points
    edited November 2009
    So you are telling me that the 52 mph I observe on a new GPS running in simulation mode in not the average speed it assumes.
    Yes, correct. Or, based on your example, we should arrive to the conclusion that even when Garmin has the average speed for a road, also that speed is completely wrong!
    Why should I assume it is the speed limit, as you say?
    I said some of them, not all. Tim confirmed on the previous page my assumption that when Garmin does not have good average speed for a road, it defaults it to the speed limit or nothing when not even the speed limit is available. In the last case the road classification is solely based on the road type.
    My point is you made an assumption that average speeds are around the the speed limit based on running the simulator.
    I never said that in such absolute terms.
    I found this happening on the bad route from Austin to Corpus Christi. It is consistent with everything I am saying. Garmin does not have realistic average speed for the roads on that route and defaults it to the speed limit.
    If it had good, realistic average speeds it would select the same route that GoogleMaps, MaqQuest and TomTom select.
    Conclusion: I will get a TomTom 920 or 930. The garmin lovers can wait for Garmin supporting the Traffic Patterns data in its maps.
  • Tim 1482 Points
    Tim confirmed on the previous page my assumption that when Garmin does not have good average speed for a road, it defaults it to the speed limit or nothing when not even the speed limit is available.
    I don't believe I said that. I have no knowledge of what is absolutely in Garmin's algorithms. I know roads are assigned road classifications. I know classifications are used to estimate a speed. I know some roads have speed limit data and some don't. Beyond that everything would probably fall into an assumption-- some based on good consistent evidence and others just guesses. Garmin has confirmed to me based on our testing that they adjust ETAs for different road classifications based on previous driving patters so we know that too.
  • aslg 0 Points
    Tim confirmed on the previous page my assumption that when Garmin does not have good average speed for a road, it defaults it to the speed limit or nothing when not even the speed limit is available.

    I don't believe I said that.
    Sixth post on page 8 from the top.
  • Tim 1482 Points
    Sixth post on page 8 from the top.
    Right. You said "Is that possible". Yes, it is possible. There is a big difference between "possible" and "confirmed".
  • gatorguy 326 Points
    Apparently a misunderstanding or mispost since Tim has clarified himself. BTW, can you give me the beginning and end points for your problem Austin route? Remind me what device too if you don't mind. That route won't be the best example, but I still want to look at it on a couple of different devices.
  • Marc 301 Points
    The thing I find ironic about all this is that if I were to post a complaint about routing, based on my local use of my 755, it would be :
    Why is my Nuvi trying to drag me back to the interstate when I know that going by back roads will get me there quicker. On my daily commute, whether I go by interstate or back roads the commute times are very close. During busy periods the secondary roads that take me to the interstate are always busy, resulting in a slower commute time if I take the interstate during that particlular time. I think people make too many assumptions based on their personal experiences. I know that the average speed on the roads that lead to the interstate are over estimated, and unless the interstate is totally jammed, my Nuvi will pick the interstate route. Undoubtedly there are some bad estimates in terms of average speeds on maps, also roads may be misclassified and maybe there is even a bug in the routing algorithms. Bitching and moaning will do little to correct this. Gator has offered a constructive way to improve things by collecting specific routes with obvious routing problems and delivering them to Garmin. Those of you that are really unhappy with the routing decisions of your Nuvi should take him up on his offer.
  • aslg 0 Points
    Sixth post on page 8 from the top.

    Right. You said "Is that possible". Yes, it is possible. There is a big difference between "possible" and "confirmed".
    I said you confirmed my assumption.
    An assumption is a proposition that is taken for granted, as if it were true based upon presupposition without preponderance of the facts
    In logic, natural deduction systems are defined as an assumption is made in the expectation that it will be discharged in due course via a separate argument.
  • I was travelling from Camarillo, CA to SFO. I checked the route on Google and saw that it was a simple straight road - US 101 N
    When I tried this route on Google maps and simulated it on my 765T, they both take me off 101 once: in Santa Barbara they have me take CA154 through Los Padres National Forest to cut off about 12 miles from the route.

    The only reason I could get my 765T (CNNAv2010.20, GPS v2.9, set to "Faster Time" with avoidances of U-turns, traffic, carpool lanes, and unpaved roads) to route me on "back roads" is if I "accidentally" got on CA1 (by setting a via point on that road). At that point, it would try to get me back onto 101 as soon as it had a chance.

    My 765T never tried to take me over to I-5 once I was on 101.
  • aslg 0 Points
    edited November 2009
    I really do not understand what else we need to discuss here.
    I came here few days ago knowing nothing about routing and thanks to all of you know I think to know enough to understand where the problem lies, at least in my case.
    Garmin does not have realistic average speed data for several road segments in its maps.
    Because the average speed of road segments is one of most relevant parameters for the calculation of routes, no good result can be achieved when the input is bad. Did you ever hear about the "shit in/shit out" principle? :)
    This is enough for me to look somewhere else. Are there other problems? It will convince me even more to look somewhere else.

    Thanks to mvl for the reference to TomTom IQRoutes on page 3.
    Thanks to darrengsaw for the reference to Navteq Traffic Patterns on page 5.
    Thanks to Boyd for the excerpt on routing calculation on page 7.
    Thanks to Tim for the http://routes.tomtom.com URL
    Thanks to all the rest of you for the frank discussion.
  • Marc 301 Points
    I really do not understand what else we need to discuss here.
    This discussion is not mandatory for anybody. If you see no need to participate in it, don't. You apparently have made your decision to move to another brand of GPS, which is certainly a valid thing to do. For those of us who want to keep our Nuvi, but would like to see things improved, this discussion may be of use.
  • gatorguy 326 Points
    ASLG, if you know where the problem lies, then you're doing much better than I am. :?

    I'm still asking for obvious and verifiable problem routes. If you do have one it would be helpful. I also understand if you'd rather just move to a different brand of gps. In any case, I'd like to move the thread in a positive helpful direction.
  • I don't have an instance where the route takes me off the highway and back on... however, there are specific routing issues posted earlier in the thread. I've posted at least three of them.
  • Gatorguy, I have one here for you that is a small example and easy to disect. All nuvi's we tried do exactly the same thing so I say it is a map/destination location quirk.
    Tried on Nuvi 760, 2010.3,4.9; 760 2009, 4.8; 750 2009; 255W 2010.2... you get the idea.

    The route for testing: Set location at N 52deg 09.010', W 122deg 08.620'
    destination 1730 Broadway Ave S, Williams Lake B.C. Canada. (the destination is the poi>entertainment>Bar>Laughing Loon Neighbourhood Pub

    You will see that the Nuvis' route you off of Hwy 97 and get you onto Broadway ave N as soon as possible all the way to your destination. Oops, correct me already, it does all sorts of weird routing depending if you enter the poi or it's address taken right from the info on the poi address, and if you have faster or shorter enabled. Sometimes even to the wrong side of the highway.(neither faster or shorter)


    My point is: Broadway ave is a frontage road that has stop signs every few hundred meters for every street and access point it crosses, it is narrow and rough and slow. Right beside it is a 4 lane highway with right of way and exits at every needed spot.
    Why are we routed off the highway in most cases to this terrible choice of route? This may shed some light as to why the Nuvi may misdirect some peoples best route scenerios.
    The kicker to all this is if you have a different destination farther down the highway it just stays on the highway as it should.
    I have had this quirk selecting cities and getting a weird detour, and I think it may have something to do with a 'line of sight' type of 'pull' that makes the nuvi head straight at it's destination if the distances are close, but then ingnoring the main highway route in favour of a secondary back road.
    See what we can do with it. :)
  • gatorguy 326 Points
    Thanks DCNuvi :)

    That still may not be the type of route I'm looking for, but we'll see.
  • I should clarify what I meant: use the POI of the Laughing Loon to test route, I used the address supplied with that POI and it routed different(more proper actually) than before.
    I guess the gps coordinates given for the Loon and the actual address are a bit off from each other, but they both go to the front door of the establishment so it is a bit puzzling.
  • [From] N 52deg 09.010', W 122deg 08.620' [to] 1730 Broadway Ave S, Williams Lake B.C. Canada.
    Running this route in MapSource (on 2010.20 mapset), it wants to get on Broadway Avenue at Proctor.

    Forcing the route to stay on HWY 97 (by adding two via points) takes the estimated time from 5:43 to 8:08 which led me to wonder if speed limits might be playing a factor.

    I simulated this route on my 765T ("Faster Time"; avoidances of U-turns, traffic, carpool and unpaved roads), and it too wants get on Broadway Avenue at Proctor.

    Simulating driving in the area shows that it thinks speed limits on various stretches are:

    1. 97 from Fox Mountain Rd to 52 08.683N 122 08.325W: 45mph

    2. 52 08.683N 122 08.325W to the pub: 35mph

    3. Avenue from Toop Road to Proctor: 25mph

    4. Avenue from Proctor to the pub: 45 mph.

    Since it thinks Broadway Avenue has a higher speed limit than HWY 97, it takes that road.
  • gatorguy 326 Points
    DCNuvi, can you post a starting address in addition to coordinates?
Sign In or Register to comment.
↑ Top