A colorful chapter in state transportation history

By David Rookhuyzen / ADOT Communications

AZ color highway signsWhen you drive by a highway or interstate marker, there is comforting uniformity to them, no matter if you are driving Interstate 8, Interstate 15, State Route 92, State Route 377, US 60 or US 191. Drivers will recognize the standard red-white-and-blue coloring and shield of an interstate, or the black-and-white coloring of a US highway or a state highway.

The size, shape, color and proportions of those signs are regulated by the Arizona Manuel of Approved Signs, which acts in concert with federal guidelines laid out in the Manuel on Uniform Traffic Control Devices, or MUTCD.

But decades ago, before all that standardization was put into place, several states decided to experiment with their highway signs by using a dash of color. That's right; instead of the normal black-and-white design, signs could be green, yellow, red, blue, brown or orange, depending on where you were driving. 

The reasoning behind adding these colors was to catch the eye of the driver. In the age before interstates, when a highway would go through a town and might involve several turns, colored signs would help drivers recognize they were still on their preferred route. So in many states, the important highways would each be given their own color, especially if they passed through large cities. 

Arizona was among the states that got into the color game, though it tried something a little different. It picked four colors for its highway signs and assigned them not to specific highways, but to specific directions. As you can see in these images from the guide of a 1961 official state highway map, markers for state and U.S. highways going north would be orange, those going south would be green, those going west would be blue, while those going east would be brown. 

Those colors weren't picked arbitrarily. The Washington Highway Department also went with this directional coloring and, according to a 1954 newsletter article, orange, green, blue and brown were the winners following field tests. It was determined that blue and brown had the best legibility when motorists were driving into a rising or setting sun. After that, orange and green were the only basic colors left in the available light-reflecting sign sheeting materials. 

But the arrival of the interstates upended the whole color experiment. The Federal Highway Administration had adopted colored signs for the interstates, and concerns grew that motorists would confuse the colored interstate sign with a colored state route sign. In the 1961 edition of the MUTCD, the black-and-white shield for U.S. Routes was spelled out. And by the mid-1960s, most states had dropped their various color schemes, including Arizona. 

It was only a brief period in the country's transportation history, but – if you'll pardon the pun – a colorful one.

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