Incorrect routing on 540 XXL

Discussion in 'Maps and Routing' started by vbaranov, Mar 17, 2011.

  1. vbaranov

    canderson Moderator

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    Of course not. Every hour or so, one might consider "Navigate to" "Recent Destination" to force a fresh look at the estimates. Requires no stops, just a couple of button presses.
     
    canderson, Mar 22, 2011
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  2. vbaranov

    vbaranov

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    To "canderson"
    A quote: "...IQRoutes is projecting arrival time based upon historical average speeds with 15 minute granularity. If you plan a 6 hour trip, do you plan to take a bottle along with you to [TMI] ... and a 50 gallon gas tank?
    <skip>
    Imperfection is assured."
    ---------------------------------------------------------
    Please review my initial post - it's a relatively small trip with less than 200 miles in distance. No need to have Stratotanker available for such trip, even the smallest car can drive 200 miles with no stops. For TT such trip is quite 'evident' to plan the route, assuming no stops along the way. I am not against IQRoutes, because it shows the really good results for the short trips, but it's nice to know when and how I may rely on TT route and do not over-assure myself with trip time and distance, but have the decent and reliable (!) expectations instead.
    Again, for less than 200 miles trip TomTom did not find the better route from the very beginning (200 mi and 3:28 is what TT declared as the first and best route), while manually entering a single waypoint (not on highway!) consistently resulted in less miles and less time on a road - either that point was rejected from the best route for a (unknown) reason, or TT even does not consider it as a waypoint.
    That would be good to find out how to deal with such situation in future and when/how to trust that "First route" (could it be an issue just for that route - quite possibly, but need to verify that). I do not consider 1,000+ mi trip, but the relatively small one, and want to know when/if I can use "Navigate to" option for an optimal trip (less miles, less time) or switch over to the planned trip/itinerary - probably, everyone may agree that, entering the destination address or use "Favorities" with route generated in seconds is much easier and simpler and is also more fan, than spending literally hours to find out, review, test and upload the best possible itinerary.
    If imperfection is assured, then its good to know at what level (distance, time, complexity, specific areas etc.) that imperfection starts to "make the difference" - just guidelines, so called "best practice".
     
    vbaranov, Mar 22, 2011
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  3. vbaranov

    vbaranov

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    To "MVL".
    A quote: "..If you post the specific start/end and forced via point of your route, I can try to debug it."

    Thank you for your proposal. :)
    I was able to "nail down" a shortest trip, when that 'effect' pops up.
    The following sub-route was tested (around one half of the whole trip), which, probably, introduces that issue:
    Lumberton, NC -> Myrtle Beach, SC.
    The 'best" route was 101miles, 1:55 hours trip.
    If entered a waypoint "Tabor City, NC", the trip is 84.9 mi, 1:47 hour (even better if avoid a center of city).
    The difference is 16 miles and 8 minutes for the initial 101 miles trip - not bad, heh? I was able to verify an effectiveness of an 'improved' route by driving via route in both directions.
    Am I wrong and could it happen that the results for a trip with "waypoint" are too optimistic? But why TT displays that route anyway?
    If these results are correct, why TT did not choose 85 miles trip as the best, based on both time and distance?
    I like an idea to drive 16 miles less on 101 mile trip - saving my time, fuel and car mileage. A question of how much more/less fuel will be required in both cases (101 and 85 miles) completely depends on driving speed along the interstate highway I-85: US Government Fuel Economy Guide
    http://www.fueleconomy.gov/feg/FEG2011.pdf
    includes a plot showing the (approx.) optimum between 47 and 55 mph for unspecified vehicle. At 75 mi/hour the fuel economy goes down by 24% - it's like paying on purpose $4.375 vs. $3.5 at pump for no reason (but, of course, it depends on the particular vehicle' economy).
    Under such circumstances, for a 'regular' vehicle to drive I may accept additional (not too many, though :) ) stops if driving along the interstate highways.
     
    vbaranov, Mar 22, 2011
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  4. vbaranov

    DavidS777

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    vbaranov - coming back to your original post...

    I'm just wondering - have you driven both routes??

    From your post - it is quite clear that you asked for an IQ route. You then requested an alternate route; and input a way-point forcing through the City. A more straight line gave you less miles. Shorter route. And reflected less travel time. You then drove that specific route; and arrived at your destination in less time than predicted. From that - you are assuming this is a better route...

    Have you driven the first route? Do you routinely drive this route? So that you are familiar with the idiosyncrasies??

    It would seem that a proper and true test of a specific route - would be to plan on leaving say on a Monday - at 9am.

    Then you make the trip leaving on a Monday at 9am - several different times.

    And you do the exact same thing - for the IQ or alternate route - leaving on a Monday at 9am - for several different weeks. Probably alternate each week - so that seasonal (longer day hours, etc.) are incorporated into each route...

    Just wondering if you have done this. Not sure. Because, I would think that this would be the only true way to know if the original IQ route was actually slower.

    You've stated that the alternate route was actually faster than stated. This could also be true of the first IQ route...

    But, not at all sure that you've driven both routes.

    However, all of your route experiments seem to be somewhat redundant. I rejoice the device works and exists; use my head to figure out how many days it will take to travel someplace cross country, etc.; and take the trip. So many road variables come up in real world - that I don't worry about which is the precise fastest route. I just use the device to get me where I don't know how to go; and am happy that it works; and I no longer have to have my wife next to me - with a bunch of maps spread out all over the place. Still have a map. Its in the glove box.

    And technically, 'fastest' is fastest with some caveats. For example - you can't have a truly 'fastest' route - while also being concerned about safety. And the TT routing algorithm definitely is also programmed to consider 'safety'. Or the number of intersections; left or right hand turns, etc.

    Obviously, just my 3 cents. :) But am wondering if you've driven both routes -a the same time, and on the same day of the week several different times...

    D.
     
    DavidS777, Mar 22, 2011
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  5. vbaranov

    canderson Moderator

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    Once the unit gets locked in on a route, traffic information can certainly cause it to start suggesting alternates, but apart from that, my own "best practice" has been as noted above -- to do a "Navigate to" using my "Recent destination" now and again (once an hour should be more than sufficient) to refresh things in an attempt to assure my schedule and the IQRoutes schedule for my arrival on various pieces of the route are still in sync. Best I can tell you Val is to give that a try on your next trip to see how it works for you.

    ? Something I don't think we ever asked you was which model of the XXL540 you have. Do you have a traffic receiver on your unit (a "T" suffix in your model or purchased separately)? That adds another whole layer of complexity to the problem of projections. "Least Cost Analysis" is a fascinating modeling problem with so many variables, isn't it?
     
    canderson, Mar 22, 2011
    #25
  6. vbaranov

    vbaranov

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    To "DavidS777": Yes-yes, I drove that way many times and have used different routes. Always started to drive at (approx.) the same time, always the same results via the certain route.

    A quote: "... I don't worry about which is the precise fastest route"
    O.K. then I do worry about that fastest route, which at the same time is the shortest one (or at least is close to that). With a 100 miles distance loosing 15 miles, while being not the fastest, seems to be an overkill and shows a heavily underoptimized route - it is acceptable if driving once, but it is 30 miles for round-trip, and that saves you during the entire year about 1,000 miles and 7 hours of your personal time if driving only each other week (how about 2 times a week? catch this). Are you willing to pay such price in terms of fuel cost, time spent on a road and your own vehicle excessive 'wear and tear' ? I don't like an idea to purchase the new tires sooner than needed and spend money for a regular service coming in too fast.
    The 'spouse' issue is a point, definitely, but it does not eliminate necessity to look for a shorter and (again "and") faster route. If such possibility exists, I will use it - no need to reject this definitely positive approach.
     
    vbaranov, Mar 23, 2011
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  7. vbaranov

    vbaranov

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    To "canderson": that is my second 540 XXL. The first one (TL) was stolen last September. This one is a gift 540S with lifetime map update, transferred from my previous unit, but no traffic anymore.

    I've used that technique you talking about (multiple times "Calculate alternative" or "Navigate to"), but the results are not clear (for me) - hard to explain and make then systematic. Maybe, I will collect more data to be a bit more certain, but using such approach seems to be not too convenient, because you should know for sure when to make such attempt and do not miss a 'point', but if you already know that, then, probably, GPS is no longer needed - everything has been already memorized as a well-known route :)
     
    vbaranov, Mar 23, 2011
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  8. vbaranov

    canderson Moderator

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    Forcing a recalculation every hour or so is a good idea for reasons discussed earlier. It does not require any special knowledge by the user, and would not be so inconvenient, I don't think. Making this a more deterministic system just isn't in the cards with current technology.

    SOME day (perhaps) there will be universal, immediate and detailed traffic information that can be used. However, even that information is dangerous when projected forward very far. I can picture a situation where the best route in one moment suddenly becomes the worst route in another, and the system would have the user "hunting" back and forth in attempts to maintain the best route. If you are familiar with a hysteresis curve, image it in those terms. It becomes a constant approximation, and never a direct best line.
     
    canderson, Mar 23, 2011
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  9. vbaranov

    vbaranov

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    ... 16 miles and 8 minutes for 101 miles trip ... Isn't it too high price? Is this common? If so, how common is it?
    Such difference should be 'felt' by the system immediately, the unit should not propose a route, which is 'a priori' neither the fastest, nor the shortest.
    TT declares 101 miles' route to be the fastest in presence of another route, which is 'shorter' by 15 miles and 8 minutes. Don't see another explanation for this, but the errors with either data or algorithm implementation, or both - verified and tested (as of today) via online TT route planner.
     
    vbaranov, Mar 23, 2011
    #29
  10. vbaranov

    canderson Moderator

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    I am just now reviewing your departure and destination, and what a fascinating mess it is. Lumberton to Myrtle Beach (no intermediate stop specified) is easily approached from three different routes, with mileages ranging from 79.5 to 93.9 miles, but with arrival times (NOT using an IQRoutes system) only six minutes apart (1:49 vs. 1:55). The slightest variation in average speed due to traffic at a specific time of day (in other words, interjecting IQRoutes into the process) could easily change the decision-making for "fastest" route, tipping it in any of the three directions of travel. You have a rather unusual situation there.

    Given that the distance difference is substantial (18% more miles between least and greatest distance) and the time differential using a "vanilla" average speed system is so relatively small (5.5% greater time from least to greatest), this would indicate that there is a substantial opportunity for traffic at a given time of day to play a major role in the results when computing best route for minimum ETA. The slightest difference in average speed on any of those routes could prove to be a tipping point.
     
    canderson, Mar 23, 2011
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  11. vbaranov

    vbaranov

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    Could happen, no doubts, but for me TT always (regardless of day, time, weekday, season, weather, humidity - what else? :) ) generated the "First route" as longer and slower than the other one. TT did never propose to drive via the "shorter and faster" route with less time whenever I use "Navigate to" option.
    As I said earlier, the "Lumberton-Myrtle Beach" trip I use as an example is a part (approx 60%) of my usual trip, because all the way down to Fayetville-Lumberton area it's just the interstate highway - not too much to play with, and because I tried to nail down where that mess starts to happen.
    A note: if driving between Lumberton and "North Myrtle Beach", then that issue did never occur, while changing the final destination back to "Myrtle Beach" immediately generates the longer and slower route, while visually it is more 'appealing' on a map.
    (BTW, the online "Route Planner" generates that route as 101 mi 1:55 hours all the time if no waypoints entered)

    The 'real-world' test drive is fully 'repeatable' at some level of precision and always confirms that the route with a 'waypoint' is better. The fastest fully-length "First route", which is 3:29 hours (as declared), is possible to 'squeeze" into 3:20 hours by driving faster, sacrificing the overall fuel economy, and the last trip via the most optimal - from my personal PoV - route, based on "multiple choice" approach, took 3 hours even and less miles - probably, the best possible case (could happened that I was lucky enough with the delays that day and time :) ).
     
    vbaranov, Mar 23, 2011
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  12. vbaranov

    GoD_GraveDancer

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    I have a similar problem on my One XL and have resorted to these forums in search for a solution.

    My One XL is roughly 4 yrs old and had never been updated until last night, when I installed version 8.010. I never had any issues with my TT until today.

    I was travelling in an strange city for my job and had to visit three different locations. I was travelling on an interstate highway and exited at the direction of TT. I was then taken through several different neighborhoods (industrial, family, etc). It seemed I was turning left/right every few hundred yards. After 12 miles of this, I came to a large highway that I was certain had to intersect the interstate. I proceeded down the highway to my destination and when leaving, asked if that road in fact connected with the interstate. It did.

    Im baffled as to why TT would not simply keep me on the interstate for a few more miles and direct me to the exit nearer my destination. After browsing through my options, I realized that "shortest route" was selected. I changed that to "fastest" and thought I had solved my problem. Wrong.

    I decided to test my "fix" and set course for the intersection of said highway and the interstate (keep in mind Im on one of the roads that I programmed into my destination and TT should only direct me to travel in a straight line). This was not the case.

    I was sent .5 mile south of the road I was on, through residential neighborhoods, PAST the interstate, told to make two lefts (which put me back on the road I was originally and roughly .25 mile PAST the intersection).

    Sorry for the winded tale, but my question is simply, "did my update to 8.010 screw with the IQRoute that you all are discussing?" If so, how can I fix this? :)

    Thanks
    Grave
     
    GoD_GraveDancer, Mar 31, 2011
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  13. vbaranov

    DavidS777

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    Grave -

    The update probably did not screw up your TT. .. I'm making this remark - because you had your unit set on 'shortest'.

    Since, you've had it for some time, not sure how it got set to 'shortest'. But shortest - almost by definition - attempts to create a straight line. If no direct straight line of road exists between you and your destination - it will attempt the straightest line possible - by use of numerous turns...

    After you set your unit to 'fastest'; did you clear your route? And ask for a complete new route? Completely clearing any routes; and then requesting a brand new route, from your current position - should have taken care of it... if you are still experiencing problems - you might try a soft reset of the TT.

    D.
     
    DavidS777, Mar 31, 2011
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  14. vbaranov

    mvl Moderator

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    The ONE XL is a 2007 model, and doesn't have IQroutes (even on app 8.010).

    Instead it uses a very old and poor road-class routing algorithm for "fastest".routes. It does all sorts of weird stuff because the "fastest" road classes are often the ones with traffic lights, etc, and not the true fastest roads.

    IQroutes uses a database of historical actual road speeds, and is much more accurate with directions.
     
    mvl, Mar 31, 2011
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  15. vbaranov

    tony22

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    Hmm, this is very interesting. Are there any differences in the routing algorithms for the models which do have QRoutes?
     
    tony22, Apr 1, 2011
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  16. vbaranov

    GoD_GraveDancer

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    Thanks for the input. I will test this again ASAP - probably Monday. Thanks again.
    Grave
     
    GoD_GraveDancer, Apr 1, 2011
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  17. vbaranov

    mvl Moderator

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    The difference is night & day with IQroutes.

    Tomtom used to give the worst directions of any brand prior to IQroutes.

    After IQroutes, it leapedfrogged the competition and offers far better directions than any other brand. Others are trying to catch up but no one has come close yet.
     
    mvl, Apr 1, 2011
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