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I read the following ETAs:

Why does Google Maps say that driving from San Francisco to Seattle via Portland is 28 minutes faster than driving from San Francisco to Seattle?

I would have thought that adding a connecting city would increase the estimate time, not decrease it.


Screenshots (taken at the same time):

GMaps: San Francisco to Seattle (mirror): 13h23min: enter image description here

GMaps: San Francisco to Seattle via Portland, Oregon (mirror): 12h55min: enter image description here

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    If you look at your own screenshots, one reads "the usual traffic", the other one "no traffic". Clearly adding a stop causes it to change its algorithm somewhat. Maybe taking traffic into account is too complicated when there are stops.
    – Relaxed
    Aug 18 '21 at 21:57
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    @Relaxed thanks good catch! Didn't expect the addition of the stop to switch it to no traffic. Aug 18 '21 at 21:59
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    Note that your screenshots are reversed
    – jcaron
    Aug 18 '21 at 22:54
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    @MichaelHarvey this I can understand in case of a path asymmetry due to eg asymmetrical traffic or one-way roads. Aug 19 '21 at 8:03
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    Am I the only one noticing that San Jose is not San Francisco?
    – NPSF3000
    Aug 19 '21 at 22:10
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The primary difference is traffic.

When you ask for the route from San Jose to Seattle, the website displays the "Leave now" option and calculates a real-time prediction based on current traffic (in this case, "the usual traffic" meaning that traffic is roughly around normal levels). You can see this because the numbers are in green; they'd turn orange or red if there was a major delay due to traffic. For such a long drive, this is only so meaningful, as traffic conditions will inevitably change and you'll surely make some stops along the way, but you can adjust the setting and it will display different time estimates (albeit within large ranges like "typically 12 hr - 15 hr 10 min").

But when you ask for directions for a multi-stop trip, it doesn't use real-time traffic information and is displaying the time "without traffic." Note that the numbers are in white (or black using light mode theming) instead of colored. Presumably, it's doing this because it has no idea how long you might stay in Portland and so has no idea even what traffic to estimate for the Portland—Seattle segment (you may be doing it at rush hour or in the middle of the night).

Furthermore, you've asked for directions to "Portland," which Google Maps has decided is a particular point around the I-5/I-405 interchange. As such, it's routed you through the city. If ask for directions to Seattle, you'll pass through Portland, but will stay on I-5, a shorter route that avoids some of the city traffic.

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    (+1) In fact, multiple destinations are not available if you chose another setting than "leave now". Changing the time or adding multiple destinations causes it to switch to a simpler algorithm than that used for a request with "leave now" between two points.
    – Relaxed
    Aug 18 '21 at 22:01
  • I believe it uses traffic for now until stop 1? Also, if you are driving, when you continue to the next destination, it reevaluates the route using current traffic at the time you leave.
    – Yakk
    Aug 19 '21 at 18:08
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    PSA: When you drag (with a mouse) the route to include a 'via' point it will keep including traffic. Super confusing. Aug 20 '21 at 6:25
  • @DavidMulder That is because 'Via' points are not stops. They are "I want to drive past here, but not stop" as far as mapping providers are concerned.
    – Justinw
    Aug 20 '21 at 7:43
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    The accident was that just south of Tacoma may have made a difference (technically that's part of "traffic", but may be worth pointing out). If you take a look at it now San Jose to Seattle shows 12 hrs 44 min.
    – Rob Watts
    Aug 20 '21 at 18:33
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When you entered the direct route, google maps suggested the route that takes you through Portland by using the highway that seemed most "direct" to Seattle and it made sure to avoid making you "enter" Portland:

enter image description here

However, when you added Portland as a stop, google maps took the liberty of finding the best route within Portland which resulted in avoiding a nasty traffic in the same "direct" highway that was suggested in the direct route:

enter image description here

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    Also google keeps track of traffic in real time. Right now I'm seeing 14H6m for the direct route and 13H3m for the indirect route. Different to the OPs times
    – Peter M
    Aug 18 '21 at 21:56
  • @peter I forgot to switch-on the traffic in the first screenshot, now I changed the first screenshot. Aug 18 '21 at 22:05
  • What's even weirder is that the route google is showing me for the "via portland" route is totally different to your screen grab. It goes via the downtown section and then loops back across the river before getting back on the 405
    – Peter M
    Aug 18 '21 at 22:08
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    @PeterM somehow I am less worried about the rise of the AI, at least for now. Aug 18 '21 at 22:11
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    Adding a stop in "Portland", without specifying an address, means stopping in the center of Portand. That's why the route has to go through the center.
    – Sulthan
    Aug 19 '21 at 13:38

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