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But the top comment at the /30 URL is not the actual answer either...

• KennyBlanken 4y ago
  Yep. Hilariously it was literally the first reply, which was promptly ignored by everyone. https://boards.straightdope.com/t/what-are-those-dents-in-i-90-outside-seattle/422061/2 https://boards.straightdope.com/t/what-are-those-dents-in-i-...
  • mike_d 4y ago
    Because the original poster replied in #3 that it wasn't that. I asked someone at WADOT about the very same thing and was told they were to create an irregular surface in one or two of the lanes (notice the street view from down thread they are only in the right most/truck lane) to prevent perfect ice sheets from forming.
    • zerocrates 4y ago
      Seems awful coincidental that they'd be exactly at the joints between the concrete, as they are in that Street View, if they were added just to make an irregular surface as you say. Maybe it's both things: they're holes from dowel bar retrofits as their look and placement sure seems to indicate, but they're only visible in one lane because the lane was purposely re- (de-?) surfaced. Or alternatively only the slow lane needed the retrofit at the time it was done just because it carried more of the heavy loads.
• dang 4y ago
  What is the best URL?