What does "Sufficiency Rating" mean for bridges?

[Wowbagger]

I was just reading The Journal News (for the Lower Hudson Valley). They state, in a table, that the recently collapsed 35W bridge had a "Sufficiency Rating" of 50%, while the Tappan Zee Bridge (a local, heavily used bridge), only has a rating of 31.1%.

The paper has a description of the term, in a footnote:
Based on numerous variables that evaluate structural adequacy and safety, serviceability and functional obsolescence, and essentiality for public use.

But, I would like to know more. Can anyone state, or point to, a more adequate description? And how concerned should one be about sufficiency ratings such as 50% or 31%?

Google gave me some details into what sorts of things are factored into this rating, but I was unable to locate a satisfactory general description.

Some folks, here at work, would also like some answers. Some of them drive over the Tappan Zee every day.

[Wowbagger]

Surely, someone here could help us shed light on this term.

I am thinking it might have more to do with the bridge's capacity adequacy, and not much to do with safety, though. So, it might not even be considered a very important factor, as far as safety is concerned.
I know that the Tappan Zee does get awfully croweded during rush hours.

Am I on the right track, thus far?

[tracer]

Is this sudden spurt of interest due to the recent collapse of the bridge in Minneapolis?

[Wowbagger]

Is this sudden spurt of interest due to the recent collapse of the bridge in Minneapolis?
Yes, but I wouldn't have brought it up, if my local newspaper didn't splatter an image of the Tappan Zee, on its front page, saying that its integrity is also being questioned.

[fuelair]

Don't know about the percents, but this is the Fed scale (you have to go a goodly way down the document - to the 0 - 9 bridge scale:
http://www.fhwa.dot.gov/policy/2006cpr/chap3.htm

[illogical]

A new car built by my company leaves somewhere traveling at 60 mph. The rear differential locks up. The car crashes and burns with everyone trapped inside. Now, should we initiate a recall? Take the number of vehicles in the field, A, multiply by the probable rate of failure, B, multiply by the average out-of-court settlement, C. A times B times C equals X. If X is less than the cost of a recall, we don't do one.

[Iamme]

A new car built by my company leaves somewhere traveling at 60 mph. The rear differential locks up. The car crashes and burns with everyone trapped inside. Now, should we initiate a recall? Take the number of vehicles in the field, A, multiply by the probable rate of failure, B, multiply by the average out-of-court settlement, C. A times B times C equals X. If X is less than the cost of a recall, we don't do one.

But these older bridges, like truss bridges, will come under greater scrutiny because let's say that few with low ratings have actually failed. You have to follow that with an asterisk that says "thus far". And the "thus far" part becomes of greater concern with age, as in the very near future, scores of these bridges could come crumbling down, inthe very same fashion as the W35 bridge.

I'm waiting for that day when all the concrete becomes brittle in all the Manhatten skyscrapers....all at once. What are they going to do then?

[my_wan]

You can read through the entire formula here;
http://www.fhwa.dot.gov/BRIDGE/mtguide.pdf

Ratings more relevant to safety are given here;
http://peoriachronicle.com/2007/08/03/bridges-under-scrutiny/

[Wowbagger]

You can read through the entire formula here;
http://www.fhwa.dot.gov/BRIDGE/mtguide.pdf

Ratings more relevant to safety are given here;
http://peoriachronicle.com/2007/08/03/bridges-under-scrutiny/ Thanks for the links, Wan. I shall read through them!

A new car built by my company leaves somewhere traveling at 60 mph. The rear differential locks up. The car crashes and burns with everyone trapped inside. Now, should we initiate a recall? Take the number of vehicles in the field, A, multiply by the probable rate of failure, B, multiply by the average out-of-court settlement, C. A times B times C equals X. If X is less than the cost of a recall, we don't do one. What car company do you work for?!