https://boards.straightdope.com/t/what-are-those-dents-in-i-90-outside-seattle/422061/30

Straight Dope Message Board

What are those dents in I-90 outside Seattle?

Factual Questions
Mister_Rik October 12, 2007, 4:59am #13
# whiterabbit:


    I have to agree that they seem oddly placed for reflectors - and
    I just drove that stretch of road earlier today.

Yeah, reflectors are usually installed on the lines, not in the tire
ruts. There are so many of these divots, so close together, for such
a long stretch of road, as to make reflectors highly doubtful. A
reflector in each dent would make the road surface blinding. (True
story: I was riding with my sister one night, returning home from a
concert in Puyallup, and we came around a curve in the highway and
entered a construction area. There were so many reflectors that my
sister literally could not see the road.) And reflectors only in the
right lane?

    I thought maybe they had something to do with traction in snowy
    conditions?

But, again, only in the right lane? The right lane is, of course,
where an extremely slow-moving piece of equipment would travel. A
construction vehicle with the type of wheels I described would indeed
be traveling very slowly. <Forensics hat on> Logic dictates that in
ordinary circumstances, the distance involved would make it sensible
to load such a slow-moving vehicle onto a flatbed truck, and
transport it to the work site that way. My theory that the vehicle
was instead driven to the site under its own power suggests that it
was too big to load onto a truck - big and heavy enough to leave
dents in the pavement as it went. </forensics hat off>

Pork_Rind October 12, 2007, 5:11pm #14
# racer72:


    Think what you want, I got it straight from the horse's mouth.

I gotta believe that there's been some miscommunication about which
divots are being dicussed. I was talking about this with some Seattle
natives last night and no one remembers reflectors ever being in
those slots. Plus, the fact that some of the recent I-5 construction
also exhibits these marks leads me to think this has to be
construction-machinery related.

Cervaise October 12, 2007, 5:27pm #15
# Mr2001:


    with this layout, you'd have to follow the reflective path like
    it's the yellow brick road.

The following answer is speculative, based on the information
provided by racer72's brother:

Consider a snowy highway. Three lanes in each direction, or two lanes
for the mountainous stretches of I-90. What's more efficient, running
a plow up one side, then back down the same side to clear the snow
off all the pavement, and then repeat both moves on the other side of
the highway for traffic running the other direction (or have two
plows running simultaneously); or running the plow once up the middle
of each side?

Obviously, it's a lot faster and more efficient to run a single plow
once in each direction. But this gives you a single plowed track up
each side of the highway, rather than clearing both (or all three)
lanes entirely.

It seems reasonable to me that if the plow goes up the middle of each
side, the resulting track will basically disregard the original lane
markings, and will instead follow the middle track represented by the
parallel-to-traffic-flow divots described. In snowy conditions
requiring plowing, there won't be a huge amount of cars on the road,
so a single lane should suffice until more extensive work can be
scheduled; and even if there is increased traffic in the single lane,
you don't want them going at freeway speeds anyway, so the volume
packing the lane will slow things down. And what's more, the "path"
of reflectors is more easily seen below the one or two inches of snow
that will still cover them, as they're recessed in the divots and the
plow won't scrape off every last millimeter of snow above the
reflective plastic.

Also: Why would the reflectors be "blinding" just because they're in
divots and there are a few more of them side to side? Just make them
a slightly different color and post some signs, and make sure the
regular lane markers are distinct, and there shouldn't be any
problem.

Again, this is just my WAG, and I await correction by more informed
posters, but as long as we're just speculating, my description makes
sense to me.

(For the record, I drive that highway also, and have wondered about
this myself.)

Gulo_gulo October 15, 2007, 6:07pm #16

I asked a friend who works for the City of Yakima about this and she
asked her boss (who used to work for the road dept) and this is what
the response was:

    The road is a concrete road, it was pored in sections. As it
    dried and over time each section started settling a little
    differently. As it settled the road started getting really rough
    and started buckling, so between each section they drilled down
    and added "ties" to bind the sections together so they couldn't
    settle in different manners, then filled in those drill areas so
    that they could be easily found if there was a problem.

Mister_Rik October 15, 2007, 10:28pm #17

I think we really need somebody to take a picture of these dents, so
that it's absolutely clear what we're talking about.

whiterabbit October 16, 2007, 12:13am #18

Unfortunately I'm now home in Idaho, so somebody else is going to
have to do it. I agree that pictures would be a good idea.

I know less than nothing about snow removal equipment, really (I just
moved to Idaho!), but my first thought was that if they're related to
that they're some sort of guide for the plows to stay nice and
centered in the right lane. I could be totally, completely wrong,
this is a WAG.

Gulo_gulo October 16, 2007, 4:42pm #19

I'm usually in that area (Yakima & on the I-5) so I'll try to
remember to have a camera with me AND get in a safe position to take
a shot. :smiley:

This won't be happening in the near near future though.

Robot_Arm October 16, 2007, 4:47pm #20
Gulo gulo:


    I'm usually in that area (Yakima & on the I-5) so I'll try to
    remember to have a camera with me AND get in a safe position to
    take a shot.

You're from California, aren't you?

Gulo_gulo October 16, 2007, 5:18pm #21
Robot Arm:


    You're from California, aren't you?

Eastern WA. But I escape a lot.

Old_Goat October 17, 2007, 2:48am #22

Yaaagh!!! They're spreading. I see them on I5 southbound going up
Southcenter Hill toward Kent, second lane fronm the curb. I noticed
they look like cuts in the concrete and they are placed at each
expansion joint. I don't think they are there stritly because the
concrete is swelling or tilting because the road is even worse at the
top of the hill and they are only on the steep slope.

The cuts are so narrow, I suspect they are some kind of inspection or
test in preparation for repaving. Anybody recall a late night lane
closure on Southbound 5 at Southcenter Hill? Funny there are no cuts
or whatever they are on the Northbound side.

Pork_Rind October 24, 2007, 5:04am #23
Old Goat:


    Yaaagh!!! They're spreading. I see them on I5 southbound going up
    Southcenter Hill toward Kent, second lane fronm the curb. I
    noticed they look like cuts in the concrete and they are placed
    at each expansion joint. I don't think they are there stritly
    because the concrete is swelling or tilting because the road is
    even worse at the top of the hill and they are only on the steep
    slope.

How about some empirical data? I was actually stopped in traffic for
a bit on southbound I-5 just before the S. 188th Street exit, in the
second lane, right over the marks. For the first time, I saw that
they did in fact cross each joint in the concrete, and were only in
the second lane as the other lanes didn't have the same visible
joints. They were clearly cut out, had some sort of rod placed as
noted in an earlier post, then refilled with concrete. As soon as
that type of expansion joint was no longer used, the marks
disappeared.

Mr2001 November 3, 2007, 8:20pm #24
Phase42:


    I think we really need somebody to take a picture of these dents,
    so that it's absolutely clear what we're talking about.

My friend drove to Seattle last weekend and I convinced him to take
some pictures. Looks like scr4 was right all along.

DSYoungEsq November 3, 2007, 11:13pm #25
# racer72:


    Finally got the answer from my brother, he is a supervisor for
    the state of Washington DOT. He works in Puyallup and originally
    wasn't sure himself. He contacted the someone that works that
    stretch of I-90, the slots were originally for recessed
    reflectors. The area gets plowed in the winter and regular glued
    on reflectors would get scraped off. The state installed the
    recessed variety about 10 years ago but have not maintained them
    due to budget constraints. There is nothing magnetic and it
    wasn't a rebar retrofit. Sorry the answer wasn't more high tech.

Well, your brother was wrong. Which is a classic example of why a
picture is worth a thousand words; I think what your brother thought
you were describing was recessed reflectors, but that's not what was
actually under discussion.

    Think what you want, I got it straight from the horse's mouth.

Well, even with a horse's mouth, garbage in is garbage out...
:stuck_out_tongue:

Good job, Mr2001!

Mister_Rik November 4, 2007, 12:01am #26
# Mr2001:


    My friend drove to Seattle last weekend and I convinced him to
    take some pictures. Looks like scr4 was right all along.

Awesome! Now I can see that I was wrong. Traveling at highway speeds
(and maybe because I wasn't wearing my glasses), I didn't notice that
the "dents" were on expansion joints, and they're not as close
together as I thought. But those still photos make it nice and clear
:slight_smile: Thanks to your friend for the photos, and thank you
for asking him/her!

Gulo_gulo November 5, 2007, 11:32pm #27

Sweet. Better photos than I could have taken. Lovely day too!

G2Jim December 2, 2013, 5:06am #28

Okay, it makes perfect sense now that those repetitive recessed areas
in the Freeway are from dowel bar retrofits to maintain the level of
the mating road sections, but it's my understanding that they were
originally filled up to the level of the surrounding road surface and
relatively smooth. I assume they have been worn away over time by the
constant beating of vehicle tires, studs, etc. to make the sunken
divots we experience today, so why can't they be refilled to level so
they're not so annoying to drive on?

If there's no other cars around I frequently drive in the left lane
to avoid them, but that's technically illegal. Also, I would think
that being lower than the surrounding surface they would accumulate
water, freeze, and cause more of a hazard and further deterioration
than otherwise. Does anyone have a contact that works for the State
that might know why they don't refill these annoying things, if they
are indeed dowel bar retrofits? They're a total pain.

Gulo_gulo December 3, 2013, 4:10pm #29

Here's some footage of the hot -n- heavy action of dowel placement.

WSDOT 1-82 Dowel Bar Retrofit

However the one time I saw it in action, it was more of an assembly
line process. There was a large flatbed with the dowels driving
slowly along the closed lane with a pack of workers scooping up
handfuls and dropping them into the pre-cut slots. A concrete pourer
brought up the rear. Not nearly as precise as the video shows.

Vm9740 June 14, 2022, 7:37pm #30

I drive to Yakima frequently from Seattle to visit family. I cannot
upload pictures to show because I am a new user to this site. My 16
year old is driving to Yakima this afternoon and was asking so we
looked it up and found this site. I will upload a picture when site
allows me to do so.

jjakucyk June 14, 2022, 9:09pm #31

I was wondering why nobody posted a Google Street View but then I saw
this is a zombie thread. Nonetheless, it looks like this is what
everyone's talking about:

And yes, those are retrofitted dowel bars. Maybe they didn't use the
best grout and that's wearing away faster than the surrounding
concrete. Regarding @racer72's comment, there are ALSO recessed
reflectors, but only along the painted lines. So there's two
different things going on.

Chronos June 14, 2022, 9:19pm #32
# Vm9740:


    I cannot upload pictures to show because I am a new user to this
    site.

Welcome to the SDMB! Actually, no users can upload pictures to this
site, even the crusty old-timers. We usually deal with this by
uploading them to imgur or the like instead, and then linking them
from there.

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