Reflective Aluminum Traffic Street Road and Highway Signs – Approved by the USDOT
Today I’m discussing reflective traffic signs or road signs. As you drive down the various roads and highways, you’d certainly be lost frequently if you didn’t have them. Back when I was a young man in my early 20’s, I spent a few winters in the Southern U.S. and was amazed at the lack of signage. Even more, I was amazed at how people knew how to get around without them.
One conversation I remember having with an old-timer went something like this…”ya’ll just travel yonda up Hwy. 357 and you’ll see a big old oak tree standin’ off by itself and there’s a road there. Ya’ll turn right on that road and drive ’til you see an old barn and ’bout half mile past you’ll take a left on a dirt road. Drive on that ’bout half a mile and you’ll see a brick house and just past that take another left and you should be there.”
Most of the time, by the way, we got lost. And that was back before cell phones, so when you were lost, sometimes you lost the whole day!
USDOT Manual on Traffic Control Devices
So, who sets the standards for these reflective traffic signs? In the US, the U.S. Department of Transportation’s Manual on Uniform Traffic Control Devices specifies not only the materials to be used on certain types of road markers, but also determines the designs to be used, the shapes, and what reflective values are needed for various areas.
The MUTCD has over 600 various sign designs specified within its covers (although I prefer the PDF version as it’s much lighter and is always as near as my computer!). You can browse here to see some of the designs. Currently the 2009 edition has been adopted by 12 of the 50 states, so some latitude is given individual states as to when to adopt the standards, although by January 15, 2012, all the states are required to adopt the standard or have equivalent state standards.
As an example of MUTCD standards, in a residential zone or school zone, “Slow Children” signage might be required to have a highly reflector “diamond grade” sheeting laminated to the sign blanks because of the over-riding concern for the safety of our children.
There are varying signage thicknesses of the materials available in the US, but the most common thicknesses used are .080″ thickness, .100″ thickness, and .125″ thickness aluminum. Depending on the size and local environmental conditions, it is often left up to a local inspector as to what thickness of material will be used on various signs. A 48″ Stop sign, for instance, may be .100″ or .125″ if specified by an individual contract, whereas a 24″ size likely would be specified at .080″ in most instances.
On very large freeway signs, you probably won’t see it, but many states specify extruded aluminum panels locked together because of the size and wind load. Alternately, many states simply require a strong framework behind the metal panel. You’ll need to check with the DOT in your state to learn which type is specified.
The MUTCD also specifies what types of metal can be used…one common types is 5052-H38 aluminum. This specifies the purity and hardness of the metal. It also specifies that the aluminum be either alodized or anodized to keep it from corroding.
The MUTCD also specifies categories by a letter/number code, such as the S1-1 which would designate a School Zone or the R1-1 which designates a Stop signage. There are also Guide markers which start with D, E, I, or M, Regulatory types which start with R, school zone types that start with S, and Warning sign types that start with a W. Not an exhaustive list, by the way, and not entirely accurate, but you get the idea.
Military bases often use many traffic marks as well and generally conform to MUTCD standards as well, but are not required to. They also have many custom signage needs, so there are many ways that signs are used on bases.
In the next article, I’ll discuss some variations in reflective traffic signs that have come around in the past 20-30 years, as well as some articles regarding custom aluminum sign posts that can be used if approved by the DOT or in private communities as well.