Reading MUTCD specs...

[Quillz]

To be honest, I actually have no clue what I'm looking at:


These are from the latest MUTCD editions I could find and use English specs.

Now, my question is basically... Are these in inches? I've tried to follow the Interstate shield design, for example, but just sort of get lost. I'm trying to recreate these in Illustrator by hand just for good practice, but are these specs designed to be used in various sign making software?

[agentsteel53]

where do those horrible shield specs keep coming from??  looks like something from the 1971 manual, but who the hell bothers to digitize those when there are so much more attractive signs out there?

[Quillz]

where do those horrible shield specs keep coming from??  looks like something from the 1971 manual, but who the hell bothers to digitize those when there are so much more attractive signs out there?

I got it from the 2009 MUTCD that's currently on the FHWA site. Thus, I assume it's what states that follow the MUTCD are supposed to be using, but I don't know how strictly it's enforced.

[agentsteel53]

good grief.  both the 56 and the 20 are hideous.  why the hell do they insist on publicizing those?

I am beginning to see where Wikipedia gets a bunch of its malevolent design principles.

[Quillz]

good grief.  both the 56 and the 20 are hideous.  why the hell do they insist on publicizing those?

I am beginning to see where Wikipedia gets a bunch of its malevolent design principles.

All the shields on Wikipedia are based on the most recent MUTCD specs. From a design standpoint, they're awful, but at least they are consistent in that sense.

Anyway, was my original assumption correct? Are all the numbers given in inches? Because if so, I think I get it, a little bit. I still find the grid unnecessarily complex, though. Seems like it'd be easier just to post all three shields and post dimensions, without all the lines and grids and things.

[agentsteel53]

All the shields on Wikipedia are based on the most recent MUTCD specs.

which makes absolutely no sense when discussing routes like US-55. 

From a design standpoint, they're awful, but at least they are consistent in that sense.

the same sentence could be applied to my bowel movements. 

Anyway, was my original assumption correct? Are all the numbers given in inches? Because if so, I think I get it, a little bit. I still find the grid unnecessarily complex, though. Seems like it'd be easier just to post all three shields and post dimensions, without all the lines and grids and things.

inches is correct.  Beyond that I didn't bother reading the spec, but I know the 1957 spec for interstate shields has a similar number of lengths and radii defined, so it looks like following the given rules will, indeed, result in the shield shown.

[Quillz]

Okay, that's what I was wondering about. I was confused because I'm used to working with images in pixels, not inches, so I see all my conceptual shields haven't been accurate to the most recent MUTCD specs. (A pixel is about 1/16th of an inch or so, so the borders on my recent US highway shield concepts have been off, for example.)

Thanks for the info.

[agentsteel53]

(A pixel is about 1/16th of an inch or so, so the borders on my recent US highway shield concepts have been off, for example.)

pixels and inches are tough to compare directly, as they depend heavily on monitor size and direction.  I tend to use a blur setting of 1.9% in Inkscape on the borders of shields I depict.  (1.9% relative to what? I will assume it is the standard deviation of the Gaussian curve with respect to the total figure size.)

[Dr Frankenstein]

These are from the 2004 Standard Highway Signs book of the FHWA (the 2010 version is not out yet, and I haven't seen these detailed specs in the MUTCD PDF). http://mutcd.fhwa.dot.gov/ser-shs_millennium.htm

The one you have is in inches; there is a metric version too.

[Quillz]

Is the metric version in meters or centimeters?

[roadfro]

Centimeters.

I still find the grid unnecessarily complex, though. Seems like it'd be easier just to post all three shields and post dimensions, without all the lines and grids and things.

It's an engineering thing. It's easier to draw something like this up, dimension it once with the generic letters, then figure out what all the sizes are by placing in a table. Sometimes there's more than two or three sizes for certain types of sign, which is where the grid comes more in handy...it would be asinine to show 5 separate pictures of a standard stop sign that are all exactly the same except for the different dimensions...

[J N Winkler]

I have often wondered if a single size is used as the default for the as-illustrated version of each sign shown in SHS and, if so, what that size is.  Many signs look quite different at different sizes--the speed limit sign is a classic example.

I don't think it matters what units are chosen as working units in the drawing program as long as the choice is consistent.  Pixels, points, millimeters, picas, etc. will all work.  If I am drawing something exactly to SHS specification, I usually use the English version of SHS because it is the easiest to work with, and set inches in SHS equal to millimeters in CorelDRAW.  Then, if I am going to be using the sign (once made) in my main sign drawings book, I will resize it down to my established working scales for either freeway or conventional-road guide signs.

[Quillz]

Yeah, it probably doesn't matter much at all, but I've switched to using inches for all my future concepts just because I think it will be easier for me. I was in the process of redoing a bunch of my concept shields, anyway.

On a slightly related note, does anyone know what the industry standard sign making software is? Because I'd imagine that's probably the easiest way to make MUTCD-compliant signs. Illustrator works well enough, but it's fairly tedious. Even with scripts, you still have to do a lot of things by hand.

[J N Winkler]

In the US there are basically two market leaders:  SignCAD and GuidSIGN.  As a collector of sign design sheets, I personally prefer SignCAD output because of the way dimensions are rendered on the plan sheet.  SignCAD by default has a relatively small dimensions block which appears under the sign and takes up relatively little of the plan sheet area, thus allowing the sign itself to be resized to take up as much of the plan sheet as practicable.  This is a valuable attribute when plans are plotted to "half size" (really a quarter of the area of "full size" because both the width and height are halved relative to the larger size) or are supplied as TIFF rasters.  GuidSIGN, on the other hand, puts the sign in the upper half of a rectangle (regardless of complexity or level of detail) with the bottom half of the rectangle being taken up by a letter spacing table.  It can be difficult to read sign design sheets which have four or six GuidSIGN drawings per sheet, arranged 2 x 2 (with lots of wasted space on the sides) or 3 x 2 (rather less wasted space on the sides).

Many state DOTs have a stipulated preference for either SignCAD or GuidSIGN, while others allow their designers or consultants to have free choice.  SignCAD is the preferred package in CA, NV, AZ, UT, CO, NM, TX, MS, PA (some PennDOT districts only), OH, IN, MO, AR, NE, IA, and KS (KDOT design office work only--some KDOT consultants use GuidSIGN--Burns & McDonnell is bad for that).  GuidSIGN has established beachheads in AK, SD, OK, IL, VA, and FL.

One reason so many state DOTs prefer SignCAD is that the sign designs can be saved separately in *.SGN files, as well as imported directly into the CAD plan sheet files.  The *.SGN files can then be distributed to a signing contractor who has the capability for automated sign fabrication and access to a sign manufacturing product from the SignCAD family, like SignCAM.  This allows the signs to be fabricated exactly as intended by the state DOT, without the need for the sign manufacturer essentially to re-draw the sign in its own manufacturing apparatus.  Some state DOTs have even experimented with exonerating contractors from all liability for sign fabrication errors provided that the *.SGN files supplied by the state DOT are actually used to manufacture the signs.

This is a typical example of a GuidSIGN sign design (just one design to a sheet in this case because the sheet is actually taken from the bidding proposal book, rather than the construction plans set)--look at how hard it is to see fine detail:



This is very typical of SignCAD output--there are many sign designs on one sheet, so the individual designs are rather cramped, but there are state DOTs like MnDOT and MoDOT which are very generous in space allocation and have just one or two "big" sign designs per sheet:



CorelDRAW, rather than SignCAD or GuidSIGN, is actually used to prepare the MUTCD illustrations.  This avoids the appearance of favoritism since, while CorelDRAW can in theory be used for production of fully dimensioned sign designs, in practice it is not well suited for state DOT production environments.

Other countries have a similar split between two market-leading sign design packages.  France, for example, has Sherpa (output is typically A4 portrait) and Corine (output is typically A4/A3 landscape).  Spain has CarDim (output typically A3/A4 landscape, program is used primarily for work on the RCE and carreteras autonomicas) and Lena (output typically A4 portrait, program is used primarily by provinces, especially in northeastern Spain).  The UK has KeySIGN (much more flexible, works as an AutoCAD bolt-on, is used for work primarily on the trunk roads and by knowledgeable local authority staff) and SignPlot (stand-alone, makes it hard to move away from canned TSRGD design concepts, outputs directly to PDF, is suitable for undertrained local authority staff).  It has long been suspected that, in order to avoid the appearance of favoritism, the DFT uses SignPlot to prepare TSRGD illustrations and KeySIGN to prepare the working drawings for traffic signs (the British equivalent to SHS).  It is conceptually possible to prepare drawings for British traffic signs in CorelDRAW, but a full implementation of Chapter 7 rules is very difficult.

[J N Winkler]

Some other examples of SignCAD output:

*  Typical TxDOT sign design sheet (Fort Worth district in this case, other districts are generally similar with the exception of Pharr)--original is 6800 x 4400 TIFF, which produces adequate but not superlative readability for the dimensioning:



*  Typical Arizona DOT sign design sheet--original is 7200 x 4800 in this case, and readability of the dimensioning is comparable to that of a TxDOT sign design sheet:



*  Typical MnDOT sign design sheet--original is 3400 x 2200, so although there are just two sign panels on this sheet, readability of the dimensioning is not much better than for the previous two state DOTs:



*  Typical MoDOT sign design sheet--there is just one design on this sheet, and the original is actually 13600 x 8800, so this is really an instance of overkill:



Note that the shield outlines are rather faint on the MoDOT sign design.  This is because MoDOT by default plots to a 34" x 22" (full size) frame, while the other three state DOTs plot to a 17" x 11" (half size) frame, and outline widths in general do not scale to plot size.  Outline widths vary from element to element and are typically specified in a state DOT's CADD manual, but as a general rule of thumb, most design offices adhere to an 0.25-mm default, which I think is too small for color boundary outlines in sign designs.

My personal rule, when making sign designs for my own personal consumption, is to use a black bounding line only for the outer edges of the design, and to leave internal color boundaries without outline.  For the external bounding line I use a consistent nonscaling width of 0.5 mm.  When I export a raster version of a sign drawing for display here, I usually blow up the sign design to 400% size, export it as a PNG (for which CorelDRAW has a built-in 10000-pixel maximum width), and then run scripts to resample the PNG down to 800 maximum width (generally by reducing the horizontal and vertical dimensions to an uniform 10% or 8% depending on the size of the input PNG and whether I want all of the drawings in a given series to be at a consistent scale).  If I blow up a sign drawing to 800% instead, I increase bounding line width to 1 mm; for 1200% I increase it to 1.5 mm; etc.

The edge blur setting Jake uses makes designs which are more aesthetically pleasing and also more commercially appealing.  My own approach is more austere and severe.

[Dr Frankenstein]

Is the metric version in meters or centimeters?

Millimeters.

[Quillz]

Alright, as a follow up question, I'm looking at the 1971 CalTRANS Interstate shield specs and once again, am lost.



Could someone please explain, even step-by-step, how I can recreate this in Illustrator? I make the shield 24''×24'', I work with 8'' numerals, but I just can't seem to follow anything else. I find this very confusing.

[J N Winkler]

Have you defined a centerline?  If you have, then assembling the shield should be relatively straightforward since you have only four circle radii (or two if you count symmetry) to worry about.  The hardest parts to do are the scallops at the top because the Caltrans spec does not kindly give you the offset of the circle centers and you will need to calculate them using trigonometry.  This is however relatively easy because you do get the width of each scallop, which allows you to derive a sine.

[Dr Frankenstein]

I made mine in Flash, making circles with the specified radii and cutting them. I positioned the top scallops by some kind of perfectionist trial-and-error (tenth of a pixel), but I'm thinking about redoing it using trig.