Aug 2Liked by Brian Potter

Overpass Georg, who crosses 10,000 bridges per hour, 12 hours per day, is an outlier and should not be counted.

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Question: does a highway overpass count as a bridge in this analysis?

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I guess New York somehow had Y2K failures in their bridges, which fortunately were quickly corrected.

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I think the "every car crosses 16 bridges a day" number could be plausible, especially if certain culverts count as bridges in the statistic.

I just checked, and my current typical 22 minute commute through the suburbs to downtown crosses 10 bridges each way (there may be a couple of culverts that I did not include, as I am not sure of their dimensions). And I live in a metro area that lacks major rivers or anything. All but one of those bridges is over other roadways. However, about 8 miles of my commute is on limited access highways. I know many commutes are only on surface streets.

When I think of all the delivery vehicles, taxis, and non-commute personal auto trips, I think it is possible to get to an average of 16 per day.

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Brian obviously gave the short answer, but to expand: the definition of "bridge" in the National Bridge Inspection Standards is:

"A structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between under copings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it includes multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. (23 CFR 650.305)"

So it's not just what you'd recognize as a bridge based on a common understanding of that word. A bunch of steel pipe culverts buried side-by-side in an embankment is a "bridge" if the sum of their diameters spans more than 20'.

These aren't *common*, because it's not all that efficient to use culverts that way--though there are probably more concrete box culverts that would fit in here--but just to be clear on what's counted.

I've never inspected a "culvert bridge" so I don't remember how they get coded offhand, but there are rules for how they get shoehorned into the database Brian is referring to, because "superstructure/deck/substructure" doesn't have obvious meaning for a bunch of pipes side-by-side. I do assure you there is a consistent methodology for them, though.

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What is considered at risk of collapse? And what is the safety standard? 3x any expected load or 3x any expected extreme weather/earth event?

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Aug 2·edited Aug 2

2012 from the excel sheet:

Row 4, Total All Bridges ~ 600k makes no sense compared to

Row 18 (Total ADT all Bridges) ~ 4.5 billion.

Vehicle miles on roads are about 6 Trillion miles annually. Or 16 million Avg Daily US miles.

Tyranny of the spreadsheet. I coined this term 40 yrs ago. Something is amiss

It’s hard to make sense of this statistic, since it implies that every day US bridges carry nearly 5 billion cars, which seems like an implausibly high number. This would require every car in the US to cross 16 bridges every day.

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