Traffic street signs include a huge variety of signs in the US, and even more in the rest of the world. Traffic street signs are regulated in every country in the world by their governments, and here in the US, the USDOT oversees every state’s DOT regarding traffic street signs. The US Government’s specific traffic street signs regulator, the United States Department of Transportation, or the USDOT, has a manual, called the Manual on Uniform Traffic Control Devices, or the MUTCD, which assigns letter and number codes to the various types of traffic street signs we drive by on a daily basis.

Letter/Number Code Designations for Regulatory Traffic Street Signs

One of the most common traffic street signs categories are the regulatory signs. In the MUTCD (which stands for the Manual on Uniform Traffic Control Devices), all traffic street signs such as stop signs or yield signs are designated with a code. Traffic street signs like a stop sign has a code – R1-1, and a yield sign has a code – R1-2, Speed Limit signs are R2-1 traffic street signs, etc. The sizes of these traffic street signs will vary for the location the sign is place in. For instance, on a highway where the speed limit is 60MPH, the traffic street signs will be larger than on a street where the speed limit is 25MPH. A Stop sign, for instance, would be 36 inches by 36 inches on the highway, but 30 inches by 30 inches on a conventional street or road.

The regulatory traffic street signs cover everything from one way streets to parking signs to prohibitive signs to weight limit signs. There are over 100 regulatory traffic street signs in the MUTCD, making it the largest single traffic street signs category in the guide. Most of these traffic street signs are white with black and/or red copy, with the obvious major exceptions of the Stop and Yield signs and a smattering of other signs such as Handicapped Parking signs.

Letter/Number Code Designations for Warning Traffic Street Signs

The next category of traffic street signs in the MUTCD is Warning Signs. Most of these traffic street signs have a yellow reflective background with black lettering/symbols. Most of these signs are diamond shaped or rectangular, and are often a combination of both. Just for fun there is one pennant shaped and one circular traffic street signs in this category. These are traffic street signs that warn of an upcoming corner, a hill, the likelihood of deer or tractors crossing, a bump in the road, etc. This category of traffic street signs will always begin with a “W,” such as W7-3.

Within the Warning traffic street signs are the temporary construction type of signs. These are used during construction or warn of temporary unusual conditions like water over the road or similar.

Letter/Number Code Designations for Guidance Traffic Street Signs

The next class of traffic street signs are the Guidance signs. This is a varied grouping of traffic street signs that includes the standard green reflective background/white reflective lettering “destination” signs – i.e. Portland 37 Miles, etc. These signs are designated with codes such as D1-1 and are usually rectangular in shape.

Letter/Number Code Designations for Route Marker Traffic Street Signs

Another classification are the route markers. These traffic street signs will mark state highways, interstates, county roads, and similar with various shaped signs, some shields, some triangles, and other shapes. The code for these traffic street signs are similar to M1-1 coding for the interstate signs. These traffic street signs vary in color, size, and shape more than any other grouping.

Within this classification are also the information signs that are coded I-7 or similar – this sign would point you to a train station. There are a few more traffic street signs within this classification such as emergency signs and recreation/cultural interest signs, but we’ll save those for a later article.

Letter/Number Code Designations for School Zone Traffic Street Signs

The last major group of traffic street signs in the MUTCD is School Zone signs, coded S1-1 and similar. These signs feature highly reflective backgrounds with mostly black copy and symbols. While this is not an exhaustive article on traffic street signs, we’ve covered most of the main sign types regulated by the USDOT here. Here is a link to the MUTCD if you want to look at several hundred pages on traffic street signs!

Learn more about the various classes of traffic signage displays.

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While these two sign types can cross over, Digital Traffic Signs and Illuminated Traffic Signs aren’t necessarily the same thing. Digital Traffic Signs are traffic signs that are typically lighted with LED’s (Light Emitting Diodes) and may have a small section that shows a digital number or series of numbers and letters, such as you might see at some airports, or digital traffic signs can also be electronic reader boards with messages for oncoming motorists.

Illuminated traffic signs, on the other hand, may include digital traffic signs, but may simply be a sign that is lighted from below with directional lamps, giving it the appearance of being illuminated. These illuminated traffic signs typically have a sensor that flips the switch on the lights as it gets dark and then reverses the process on the illuminated traffic signs as daylight arrives in the morning.

Illuminated Traffic Signs

Typically, illuminated traffic signs look like this. As you can see, on the rail below these illuminated traffic signs and to the outside of the service platform there are lights affixed to the rail that shine onto the reflective sign surface, making the signs into illuminated traffic signs that are highly visible at night, which is a good thing, especially if you’re new to an area or passing through.

Digital Traffic Signs

Digital traffic signs are different in that they typically use LED’s, as mentioned earlier, and can look either look like this…

…..or like this…..

The digital traffic signs like the one above are a “message center” type of sign that is programmed remotely

with a new message as needed…typically something like “Road Construction starting August 1st and Never Ending…hahaha” or the like.

The digital traffic signs similar to the one on the right are generally programmed from a booth and will say something like “Open” or “Lot 2 Full” or similar. Obviously these digital traffic signs are more expensive than your standard aluminum panel road sign, especially the message center style of sign…the digital traffic signs on the left, for instance, cost taxpayers in excess of $100K each.

Who to Check with Regarding Illuminated Traffic Signs and/or Digital Traffic Signs Regulations in Your State

In the previous article I discussed standards for reflective road signs which are set nationally by the US Department of Transportation (USDOT), or by local states conforming to the USDOT’s Manual on Uniform Traffic Control Devices (MUTCD). This manual gives all the regulations for various aluminum traffic signs, but doesn’t offer regulations regarding both digital traffic signs and illuminated traffic signs. However, any digital traffic signs or illuminated traffic signs used on an interstate or state highway will still need to be approved by the state DOT or USDOT.

There are many road sign manufacturers in the US, but only a few that manufacture the big message center LED digital traffic signs. A few more make the panel-type LED digital traffic signs. Due to the complexity of the digital traffic signs/message center signs, however, many companies can sell them as distributors.

One other type of internally illuminated traffic sign is used almost exclusively at airports or public transportation facilities. These are a standard ballast-driven, fluorescent bulb, internally illuminated traffic signs with a decorated polycarbonate face, one or two-sided, similar to the one shown here.

Obviously, these internally illuminated traffic signs needs to have a power source, so it’s not practical under many circumstances to use this type of sign in rural areas, plus these internally illuminated traffic signs are considerably pricier than standard aluminum traffic signs. They are also custom illuminated traffic signs and are not covered in the MUTCD, but are typically regulated by local authorities. There are many companies that manufacture these types of internally illuminated traffic signs, but all of them still need to be approved by the proper certifying authority.

Click here to see other types of signs designed for traffic usage.

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As you drive down the various roads and highways, you’d certainly be lost frequently, especially at night, if you didn’t have reflective traffic signs and reflective road signs. 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 reflective traffic signs and reflective road signs or in many cases, any road signs at all! Even more, I was amazed at how people knew how to get around without them.

One conversation I remember having with a Southern gentleman, an old-timer in Mississippi, 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!

Do Individual States or the USDOT Delineate the Guidelines for Reflective Road Signs and Reflective Traffic Signs?

So, who sets the standards for these reflective traffic signs and reflective road signs? In the US, the U.S. Department of Transportation’s Manual on Uniform Traffic Control Devices specifies not only the reflective road signs and reflective traffic signs to be used on certain types of roads, but also determines the designs to be used, the shapes of the reflective traffic signs and reflective road signs, and what reflective values are needed for the reflective traffic signs and reflective road signs in various areas.

The MUTCD has over 600 various designs specified for reflective traffic signs and reflective road signs within its covers (although I prefer the PDF version as it’s much lighter and is always as near as my computer!). 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 for reflective traffic signs and reflective road signs, although by January 15, 2012, all the states are required to adopt the standard or have equivalent state standards for the reflective traffic signs and reflective road signs in their state.

As an example of MUTCD standards regarding reflective traffic signs and reflective road signs, in a residential zone or school zone, “Slow Children” signs are required to have a highly reflective “diamond grade” reflective sheeting laminated to the reflective traffic signs and reflective road signs because of the over-riding concern for the safety of our children.

General Guidelines from the MUTCD Manual for Materials Used for Reflective Road Signs & Reflective Traffic Signs

There are varying thicknesses of aluminum material available for reflective traffic signs and reflective road signs in the US, but the most common thicknesses used are .080″ thickness, .100″ thickness, and .125″ thickness aluminum. Depending on the size of the reflective traffic signs or reflective road signs and local environmental conditions, it is often left up to a local inspector as to what thickness of material will be used on various reflective traffic signs and reflective road signs. A 48″ Stop sign, for instance, may be .100″ or .125″ if specified by an individual contract, whereas a 24″ Stop sign 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 sign panels locked together because of the size and wind load. Alternately, many states simply require a strong framework behind the metal panel of these reflective traffic signs and reflective road signs. You’ll need to check with the DOT in your state to learn which type of reflective traffic signs and reflective road signs is specified for your project.

The MUTCD also specifies what types of metal can be used in the construction of reflective traffic signs and reflective road signs…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 of reflective traffic signs and reflective road signs by a letter/number code, such as the S1-1 which would designate a School Zone or the R1-1 which designates a Stop sign. There are also Guide signs which start with D, E, I, or M, Regulatory signs which start with R, school zone signs that start with S, and Warning signs that start with a W. Not an exhaustive list, by the way, and not entirely accurate, but you get the idea about how reflective traffic signs and reflective road signs are organized in the MUTCD.

Military bases often use many reflective traffic signs and reflective road signs as well and generally conform to MUTCD standards as well, but are not required to. In the next article, I’ll discuss some variations in traffic signs that have come around in the past 20-30 years, as well as some tips regarding reflective traffic signs and reflective road signs that can be used if approved by the DOT or in private communities as well. You can check this to have a view of the common road signs as approved by the DOT.

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