
New Analysis Confirms Why the Skagit River Bridge Collapsed - curtis
http://gizmodo.com/new-analysis-confirms-why-the-skagit-river-bridge-colla-1785842162
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mannykannot
There is no mention of installing a sturdy beam across the road slightly lower
than the least clearance, just a suggestion that the least clearance should be
reported, and an extended discussion of the multiple (and rather unsurprising,
IMHO) ways in which the pilot car system failed.

I am reminded of the half-assed measures that were taken to mitigate the risk
of DC10 cargo doors blowing open, prior to the Turkish Airlines crash in
Paris. Am I missing something here?

~~~
ubernostrum
Sadly, there's not much that can be done to fix humans.

The elevenfooteight bridge now has a traffic light which goes red and stays
red on detecting an overheight vehicle, with a lit-up sign saying "OVERHEIGHT
MUST TURN". It's still getting hit by overheight vehicles.

And then there's the lengths that had to be gone to in Syndey to stop
overheight vehicles entering tunnels:

[https://www.youtube.com/watch?v=NoTMC-
uxJoo](https://www.youtube.com/watch?v=NoTMC-uxJoo)

~~~
mikeash
It depends on what you want to fix.

The 11'8 bridge does indeed seem a lost cause as far as preventing people from
ruining their overheight vehicles. But the problem for the _bridge_ has been
solved: they installed a beam in front of the bridge which takes the impact.

The same sort of thing could be done with this bridge. Install a sturdy beam
ahead of the structural bits. You won't stop people from driving overheight
vehicles onto the bridge, but you will stop them from destroying the bridge in
the process.

~~~
maxerickson
It depends on if you want to allow max height vehicles to use the center lanes
or not.

I guess you could have a mechanism to raise the warning beam and only activate
it after direct communication with the driver.

~~~
mikeash
You could have sacrificial beams in front of all the important ones throughout
the bridge, if you're worried about lane changes. That may not be worthwhile
though.

~~~
maxerickson
My (not well studied) understanding is that all of the beams are important on
this style of bridge.

That's sort of the other way of looking at the problem. The bridge isn't
overbuilt enough.

~~~
mikeash
Right, so you'd need a lot of sacrificial beams if you wanted to defend
against lane changes in the middle of the bridge. Probably easier to add
structural redundancy instead.

------
fnj
"The driver was following the pilot car too closely: more than half the
recommended distance for adequate response (400 feet, or a five-second
response time, instead of the recommended 865 feet, allowing for a 10-second
response time)."

Er, that's _less_ than half the recommended distance. How did the copy editor
let that through?

~~~
sverige
The braking distance increases with velocity. The measurement is in seconds,
not feet.

~~~
mikeash
Following time and following distance are linearly related. Either way, it's
less than half.

~~~
sverige
Braking distance is not linearly related to following distance. Braking
distance is what is being referred to here.

~~~
mikeash
They're pretty clearly talking about following distance there.

------
13of40
"that doesn’t account for the economic losses that the area felt because they
and visitors no longer had access to the interstate"

I've got a pretty awesome picture of me and my son standing in front of that
empty section of bridge from the detour route. They essentially routed I-5
traffic into the town and across another bridge. If I had to guess, the stores
in that area probably made more money during the detour...

------
6nf
The sheer number of things that had to go wrong for this disaster to happen is
impressive.

~~~
khuey
Indeed. The system works, most of the time.

------
PhantomGremlin
I haven't seen this image posted recently. It's wonderful:
[https://www.reddit.com/r/funny/comments/4ehaka/on_the_road_t...](https://www.reddit.com/r/funny/comments/4ehaka/on_the_road_to_success_there_are_no_shortcuts/)

    
    
       ON THE ROAD TO SUCCESS,
       THERE ARE NO SHORTCUTS.

------
hga
This is the first I've heard that the I-35W Mississippi River bridge in
Minneapolis was "fracture critical", and even if it was, the design flaw of
too small gusset plates would possibly make that moot when one of them gave
way, since others that were too small would then fail more easily.

------
sintaxi
> The authors recommend changing policy to report the lowest vertical
> clearance for bridges, rather than the highest

Common fucking sense.

~~~
techsupporter
> Common fucking sense.

No, it isn't, and this is one of the problems when the "general public"
comments on engineering things. It's not that people aren't _capable_ of
understanding; they lack the _experience_ to understand why something is the
way it is.

Someone on /r/seattle[0], where this was recently posted, put it more politely
than I:

===

It's because that extra two feet can be valuable when carrying oversized
loads. Frankly, this _all_ falls on the driver of the oversized vehicle, the
driver of the pilot car, and the hauling company.

\- The driver of the oversize vehicle is responsible for knowing his load
height. A hauler I've worked with before has it in their manuals that the
driver must personally measure the load if there is any question. That driver
must also stay far enough back of the pilot car to stop in case of a problem.

\- The driver of the pilot car fucked up royally by missing the sound of the
height-verification antenna hitting the bridge. That is a massive error that
should see that pilot car driver drummed out of the industry.

\- The hauling company erred drastically by not pre-running the route, or at
least the low clearance segments, to verify where the clearance exists. That
is "oversize hauling 101."

The article says the state "rubber stamped" an oversize permit. No, they
didn't. The hauler certified that the hauler had pre-run the route. It is
required that the hauler state that the route has been verified when the
permit is issued.

"It is the responsibility of the permit applicant to check, or prerun, the
proposed route and provide for safe maneuvers around the obstruction or
detours as necessary."

\- WSDOT bridge clearance tool
([http://www.wsdot.wa.gov/data/tools/bridgeclearance/](http://www.wsdot.wa.gov/data/tools/bridgeclearance/))

0 -
[https://www.reddit.com/r/Seattle/comments/50167q/new_analysi...](https://www.reddit.com/r/Seattle/comments/50167q/new_analysis_of_the_2013_skagit_river_bridge/)

~~~
TwoBit
What you are saying makes no sense and certifiably wrong because a team of
experts recommended changing the standard to ensure min height is always
reported, not max height.

~~~
ghshephard
Both heights should be available. If only _one_ number is to be reported, then
yes, report the lowest height. But, for more advanced scenarios, such as
electronic Maps, you should report the lane heights as appropriate.

