How do maps apps (Waze, Google maps, etc) actually calculate best routes and time for distance travelled? Is it all from tracking?
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It’s partly from knowing the speed limits of the road, partly from mass tracking, and partly from having access to information about roads under construction.
* **Speed limits:** If you can get from Point A to Point B via a freeway or via a surface street in roughly the same distance, the app knows that the freeway will be faster because it has a faster speed limit.
* **Tracking:** The app’s server can determine from other people’s GPS data if there’s a traffic jam. If there are a bunch of phones moving slowly or sitting still in the middle of the road, then the server assumes there’s a traffic jam and tells the app to try find the next-best route. (Hilariously, [an artist took advantage of this last year by walking around with a little red wagon full of rented cell phones and “burner” SIM cards to fake a traffic jam](https://www.vice.com/en/article/9393w7/this-man-created-traffic-jams-on-google-maps-using-a-red-wagon-full-of-phones).)
* **Access to road closure information:** Sometimes Google is given or is able to access information on road closures. That way, even though the mass tracking doesn’t show any traffic jams on the closed road, the app won’t bother trying to route you that way.
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