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Big Dig light fixture comes crashing down
By adamg on Thu, 11/10/2011 - 7:41am
But not because it was held up with rusty paper clips but because a car on the top level of a car carrier knocked into a bunch of light fixtures, the Globe reports. And isn't it nice to see that Big Dig designers paid homage to Storrow Drive by designing a tunnel with height restrictions?
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Comments
What's with the screwy faux-ish headline/article?
I know this isn't the biggest gripe in the world, but the wording above seems to join in the sensationalism about what's just another traffic story. Sure, the fixture came down - but instead of implying that it did it on it's own, wouldn't a more appropriate one make it clear that it was knocked down?
And the snarky closing line about height restrictions - I can't recall the last time I was in a roofless tunnel, so I don't think it really should come as a shock to anyone that big cargo vehicles need to pay attention to details like clearance.
True, it was a standard-issue traffic accident
But it's noteworthy because of the tunnel's past issues with light fixtures. And yes, while tunnels have roofs, it's interesting that a $15-billion project was not designed to accommodate trucks that are otherwise roadworthy.
Meh.
Large cargo carriers are restricted or even outright prohibited from all sorts of passage - many bridges, intraurban streets, parkways. Tunnels too.
As far as cost goes, it's probably a reasonable first order approximation to imagine that construction costs for any large tunnel increase as some fraction of the square of the cross-dimension (ie height or width of roadway). For the sake of argument let's assume that two-thirds of the cost of the Big Dig was in design, overhead, and construction infrastructure, and only one-third was directly related to the cost of earth-moving and material construction.
That would mean making the tunnels 25% taller would be expected to increase the cost by ~17%. Think it would have been worth it to tack another $2.5B onto the final cost so that once a decade some moron with a two-story car carrier would get to drive through unhindered? (And yeah I know - IANACE.)
In other words, $15-billion
In other words, $15-billion doesn't buy what it used to.
Legal maximum height of trucks
in Massachusetts without requiring an overheight permit is 13'-6". The clearance in the I-93 Big Dig tunnels is posted at 13'-9", but that's from the roadway to the bottom of the overhead signs in the tunnel, and not to the light fixtures or the tunnel ceiling itself.
And Jeff F is correct. Increasing the tunnel clearance to even 14'-6", which would have required lowering the roadway further, and not raising the ceiling, would not only have increased construction costs and created additional ground water removal issues, but would have resulted in excessively steep grades for both the I-93 approaches as well as all the entrance and exit ramps connecting the tunnel system with the surface streets.
"Ducka You Head...
...lowla bridgeada" or tunnel in this case.
Given the fact that this was a car carrier, its actual height could have varied quite a bit depending on what was put on top (assuming it wasn't one of those car carriers that have a top rack around the cargo). This wasn't a U-Haul driven by clueless college students trying to trundle down Storrow Drive, so it's reasonable to conclude that it's on the professional commercial hauler to know what his actual height is and not just roam about hoping things will fit.
The Big Dig can be criticized on so many fronts, not being able to accommodate every idiot that gets behind the wheel of a big truck shouldn't be one of them.
Plus there might be limits as
Plus there might be limits as to how low the dig could be whilst still being in about the same place. The dig tunnel goes above the aquarium stop on the blue line (looking from the west entrance mezzanine, you can see where the ceiling lowers to accommodate it).