"Corrugated" vs "flat-panel"

[cjk374]

Down here in God's country (Louisiana  ), the BGSs and BBSs have undergone a transformation in the last 15 years or so.  They have gone from being flat-panel to corrugated (strictly my terminology.  I don't know what the real names are  ).  Why the change  --money? easier to work with?  IMHO, I would think flat-panel would be easier to maintain and cheaper...but I also don't know much about the behind-the-scenes action that goes on with sign construction costs.

[Michael]

From JP Wing's Upstate NY Roads Site FAQ:

6. Why do interstate signs in other states have "slats" on the back of them but they don't in New York?
There are two types of sign manufacturing methods used in the United States when it comes to freeway signs. Most states opt to use "extruded" sign panels, which are made with the 12-inch strips of extruded metal bolted together to the desired size of the sign. The strips are then covered with the desired sign sheeting material and in most cases, the legend (lettering, etc) is riveted on from pre-cut reflective letters. In some instances, reflective sheeting is used. The majority of extruded panels do not have rounded corners, instead the border of the sign is rounded. In New York (and some other states), "incremental" panels are used, which are made of sheets of aluminum or wood riveted together to the desired shape and mounted on crossbars. Again, reflective sheeting and legend is applied. In most instances New York opts to use reflective sheeting for the lettering and the background. Incremental panels have a service life that is about half as long as extruded panels, allow the corners to be rounded and cost about half the price of the extruded panels.

[Quillz]

I prefer the incremental panels only because I like seeing actual rounded corners.

[Michael]

I prefer the incremental panels only because I like seeing actual rounded corners.

Me too.  I think square sign corners look sloppy.

[Ian]

Delaware used to use those "flat-panel" (round corners) signs up until the mid-2000's. Since they've switced to the "corrugated" type (square corners), DelDOT went on a genocide on all of their perfectly fine flat-panel signs leaving very, very few left.

[cjk374]

[/quote]

I had to bring ol' Frankensign    back from the grave to answer a question I was about to ask....y'all kept talking about rounded and square corners, and I thought I missed something about the topic I started.  Apparently in the northeast, your flat-panel signs came with rounded corners.  In Louisiana, ours had square corners.   

[Ian]

There have been a ton of new PennDOT signs installed lately that are flat-panel yet still with square corners.

[Mergingtraffic]

So is this extruded?

AAroads

[J N Winkler]

Hard to say, but my guess would be extrusheet construction on the left and extruded aluminum on the right.  I can't see panel joins on the left-hand sign but the sign surface has a slight "rippled" look which is generally associated with extrusheet signs.

[The Premier]

I'll go with corrugated, so you can remove a section without having to make new signs. That's what they did when Ohio phased out the 65/55 speed limits on rural interstates.

[myosh_tino]

I prefer the incremental panels only because I like seeing actual rounded corners.

There have been a ton of new PennDOT signs installed lately that are flat-panel yet still with square corners.

Not all incremental panels have rounded corners.  California's BGSes are definitely not the corrugated/extruded-type but still retain square corners.

[J N Winkler]

There are actually four major types of sign construction I am aware of that are in common use:  laminated panel (often can be identified by a horizontal panel join, and back is usually flat metal), extrusheet (can look like extruded aluminum if horizontal stiffeners are used, but the front face of the sign typically has a "rippled" appearance because large flat aluminum panels are used as the substrate for the reflective sheeting and are not held in place under tension), extruded aluminum (multiple panel joins, typically with sheeting lapped over each extrusion), and formed panel (tends to have vertical panel joins and is enclosed by a removable sign panel frame).

Any of these sign types can be used with demountable or direct-applied copy.  If demountable copy is used, it can be either button copy or flat aluminum cut to shape with retroreflective sheeting applied over the whole surface.  If the latter is used, the corners within each letter can be either perfectly square or slightly rounded to allow safe handling.

Extrusheet signs do not necessarily have rounded corners.  Kansas DOT has used extrusheet construction in the past (I think it is now being phased out in favor of extruded aluminum), but always with unrounded corners.

Within each type, there are state-specific variations in construction.  For example, Oklahoma DOT uses extruded aluminum signs but places a stiffener strip at each vertical edge, which partially hides the extrusion ribbing from casual viewing.  I have long suspected (but do not know for sure) that the stiffener strip is there to reduce the chances of the sign being torn apart in a tornado, with the individual extrusions becoming dangerous missiles.

[wriddle082]

There are actually four major types of sign construction I am aware of that are in common use:  laminated panel (often can be identified by a horizontal panel join, and back is usually flat metal), extrusheet (can look like extruded aluminum if horizontal stiffeners are used, but the front face of the sign typically has a "rippled" appearance because large flat aluminum panels are used as the substrate for the reflective sheeting and are not held in place under tension), extruded aluminum (multiple panel joins, typically with sheeting lapped over each extrusion), and formed panel (tends to have vertical panel joins and is enclosed by a removable sign panel frame).

Any of these sign types can be used with demountable or direct-applied copy.  If demountable copy is used, it can be either button copy or flat aluminum cut to shape with retroreflective sheeting applied over the whole surface.  If the latter is used, the corners within each letter can be either perfectly square or slightly rounded to allow safe handling.

Extrusheet signs do not necessarily have rounded corners.  Kansas DOT has used extrusheet construction in the past (I think it is now being phased out in favor of extruded aluminum), but always with unrounded corners.

Within each type, there are state-specific variations in construction.  For example, Oklahoma DOT uses extruded aluminum signs but places a stiffener strip at each vertical edge, which partially hides the extrusion ribbing from casual viewing.  I have long suspected (but do not know for sure) that the stiffener strip is there to reduce the chances of the sign being torn apart in a tornado, with the individual extrusions becoming dangerous missiles.

I'm pretty sure that both Kentucky and Illinois also use the stiffener strips on their extruded signs.

Here is a rough list of what the states I've been to generally use:

Alabama:  incremental (corners not rounded)
Arkansas:  newer signs are extruded, older signs are incremental (corners not rounded)
Colorado:  extruded
Florida:  incremental (corners rounded), but IIRC the blue service signs are extruded
Georgia:  extruded, but I've seen newer exit gore signs that were flat panel with rounded corners
Illinois:  extruded
Indiana:  extruded
Kentucky:  extruded
Louisiana:  extruded
Maryland:  extruded
Massachusetts:  extruded
Michigan:  extruded
Mississippi:  mostly extruded, but I've also seen this strange combination of extruded and flat panel on older signs
Missouri:  extruded, but I believe they've used flat panels (rounded corners) on their exit gore signs in the past
Nevada:  extruded
New Hampshire:  extruded
New Jersey:  extruded, but NJ Turnpike used to use incremental
New York:  incremental (corners rounded)
North Carolina:  incremental (corners rounded)
Ohio:  extruded
Pennsylvania:  extruded
South Carolina:  extruded
Tennessee:  extruded
Texas:  extruded
Virginia:  incremental (corners rounded)
West Virginia:  extruded

Feel free to add to this list, correct it, or knock me upside the head for spoiling this thread  

[hbelkins]

I've seen some "incremental" signs in Pennsylvania.

[SignBridge]

I've always thought New York's incremental signs were cleaner and more professional looking than the extruded type seen in other states. I was surprised to read above that incremental sign panels have a shorter service life. Are we sure that info is correct? Some BGS's in NY have been around for a very long time like 30 years or more.

[Scott5114]

Just because a sign is still up doesn't mean its proper service life didn't expire long ago

[SignBridge]

Point well taken Scott, and in some cases very true. But there are many incremental type signs here that are 25 years old and still in very good condition. And I maintain that the clean, flat, smooth look of incremental signs looks far better than the rippled look on the face of many extruded signs.

[Michael]

And I maintain that the clean, flat, smooth look of incremental signs looks far better than the rippled look on the face of many extruded signs.

I agree.

[roadfro]

Any way we can get some closeup pics of each of these types of signs? I'm having a hard time picturing the differences, as described by JN Winkler, in my mind.

[J N Winkler]

Extrusheet:



Extruded:



Formed panel:

[myosh_tino]

Is this an "extruded" sign?

This sign (photo from the AARoads gallery) is at the Sacramento Airport and you can clearly see the ripples on the right side of the sign and there are no vertical seams like most signs in California.  I guess the rounded corners are a dead giveaway too.

[J N Winkler]

Yup, it is an extruded-panel sign.  But I don't think formed panel signs (with the vertical lines) are actually in the majority in California.  Caltrans also makes extensive use of laminated-panel signs, which typically have a single horizontal join if the overall sign is high enough that multiple laminated panels have to be joined together.  I had a quick look through the AARoads photos but could not find a suitable close-up photo of a laminated sign panel with a horizontal panel join.

[Dr Frankenstein]

I'm surprised to see this type of sign with cut corners.

[roadfro]

So would this be an example of extrusheet or formed-panel sign? This is a typical overhead BGS design for Nevada DOT. There appear to be vertical joins, and the backside of the signs appears to show frames between panels.

From AARoads: US 395 (I-580) southbound just past I-80 onramps in Reno. (Note: Due to a widening project, this sign bridge no longer exists.)

[J N Winkler]

I don't think it is an example of either type.  I think it's an example of a form of sign construction, which I have found only in Nevada, where strips of sheet metal are riveted directly to stiffeners running along their edges and the sign panel is framed on the edges but is not otherwise reinforced.

A similar design, but without the edge framing, is used (or at any rate used to be used) on rural lengths of I-80 east of Reno.  I think these sign panels are designed to flex slightly in the wind.  They are also mounted on four-legged structures, each one of which acts like a tripod.

Nevada is actually quite an interesting state in terms of sign panel construction.