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Do map updates know about temporary road closures?

Yesterday I drove along MS Hwy 4 from Senatobia to Holly Springs MS. My Drivesmart 61 lmt-s wanted me to get off of Hwy 4 at Hwy 309 and go to Hernando Road then Holly Springs. This is a 12 mile detour from what is normally a 34 mile drive. All the while I'm driving prior to the junction of 309 I'm trying to figure out why Garmin wants me to drive further than necessary. However shortly after passing where my GPS wanted me to turn, I find that I am on a brand new bridge that surely would have had that section of road closed for a few months.

So that experience added to more than a few other experiences I've had where my gps seems to know about stuff happening even though it is not given access to traffic info via fm receiver or phone app. In some cases the routing given by my GPS has been spot on as was a routing south and east of Birmingham AL due to construction and closures along the more direct route going almost into Birmingham and up the northeast side. Yet others experiences leave me puzzled why it avoided the usually faster and more direct route.

Maybe as a user of GPS devices I'm supposed to accept my proper role as "navagationally challenged" and blindly accept the directions given to me by Garmin, Google or what ever. But I can't and don't. I win often enough to feed my ego as superior to the dumb machines others think smart.

From my viewpoint, I'd rather Garmin let me know that it is detouring me and for what reason. Even if all they could tell me is that their data shows that section of Hwy 4 being closed. At least I wouldn't have been potentially dangerously distracted while driving by checking alternate sources for why and I should go a much longer route than a more direct route.

Have any of you any knowledge of how Garmin implements this behavior?

Are sections to be closed temporarily just seen as unusable for the entire time you have that particular map version or does the map data contain the scheduled dates and times?

Is this info actually in the map file or is it in an ancillary file that may be updated during one of the other times the device might be connected to Garmin Express?

Certainly something I'll ponder on while driving. And it certainly adds to the ambiguity in routing sometimes seen when troubleshooting issues posted by others.


  • Tim 1500 Points
    I don't know about the data structure of where this is stored, nor the exact scenarios of when it does or does not get updated. However I do know that the map data does allow for a schedule of road closures. This could be something seasonal in nature, like a particular road is typically closed from November 1–April 1, or it could be for a scheduled more temporary closure.
  • privet01 231 Points
    Thanks for the information. Do you happen to know if the data-set also contains info about preferred routing around some large congested metropolitan areas?

    Sometimes I seem to be taken a longer way around when the old and direct way are faster, shorter and often less congested. Though I don't do them often enough to say that it may not have been due to scheduled closures that may not have happened on that particular day.
  • Tim 1500 Points
    The map databases do contain data relative to the expected travel speed at various times of various days of the week. That would impact the route generated around larger cities.

    Also, longer routes are calculated by using what could be thought of as a series of pre-calculated intermediate routes. So in a route from A to Z the map already knows (sort of, like precompiled) the best way to get from F to H (via G) so it can skip doing that "by hand" so to speak.
  • The mapping data in Garmin like most other stand-alone GPS units come from the company "Here" and the roads are updated from a variety of sources including volunteers like myself. Some volunteers are quite zealous and mark temporary closures, but the update interval of Garmin and then the end-user are random (best case 6 monthly) it is possible to get closure updates after they have reopened. I personally leave temporary closures alone.

    If you log into 'MapCreator" you too can update the source database and the more that do, the closer to the real world the data gets. It still comes down to how long since Garmin updated from Here and how long since you updated from Garmin, then it comes down to what preferences (fastest, shortest etc) and what avoidances (unpaved roads, toll roads etc) you have set.

    Of course, if you use the less popular Google maps, (yes Here is several times bigger in the mapping information world and provide most offline mapping), then the update is totally different and invariably online, so you see the latest Google information.
  • Boyd 2033 Points

    The mapping data in Garmin like most other stand-alone GPS units come from the company "Here"

    Can you give some examples of "most other standalone GPS units"? ;) I thought Garmin and TomTom were about all that's left today, and TomTom has their own data.
  • Not in the market today, being happy with what I have, but what happened to Hema, Magellan, Alpine, Navman, Becker, Rand McNally, Navigon, DeLorme, Mio, Braketron, Axion plus the 21 vehicle manufacturers.
  • Boyd 2033 Points
    edited December 2019
    Mio was bought by the company that owns Magellan and discontinued many years ago. Magellan makes some fleet devices and an off-road device, AFAIK there are no regular automotive units and they also discontinued their handhelds. DeLorme and Navigon were bought by Garmin and their devices were discontinued. I thought Bracketron just made mounts, did they also make GPS devices? As for the rest.... no idea, you can Google those yourself. ;)

    But it's all about Garmin today, with TomTom making a few devices. The dedicated GPS market is all but dead today, just look at what's happened to this site which is basically a ghost town compared to 10 years ago. And your own statement sums it up pretty well "not in the market, being happy with what I have".

    I would be interested to see the source of your claim that HERE is "several times bigger in the mapping information world" as that doesn't sound quite right to me, although they probably do provide most offline mapping, by virtue of the fact that Garmin uses them. AFAIK, Google does not provide offline mapping to third parties, their whole business model is based on online use so they can scrape information about their users.

    I'm a registered HERE developer and use their maps on my own site at Also a registered Bing developer, but pulled their maps from my site. I just don't care for their restrictive terms and conditions, and HERE seems like a much more relaxed and friendly place. As for Google, I registered with them long ago, built a site with their API and shut it down after a few years. Google only allows their map data in their own user interface, which I don't like. My own site is built with open source software and HERE has no problem with that.
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