Why are State Road Signs Shown as Round on Maps?

One thing that always puzzled me is why state roads are marked on maps with round markers. Indiana has never had round state route markers (unless they were installed by mistake, such as one that was at the I-465/SR 37 interchange [exit 4] on the south side of Indianapolis). Why are they shown that way on maps?

Prior to 1925, state route numbers were shown on Indiana maps as just numbers written along the side of the route. The state road markers installed were painted on poles along side the road in the rough shape of the state on a rectangular background, with the word “STATE” above the number and “ROAD” below it. In 1925, the American Association of State Highway Officials (AASHO) came out with a manual of recommendations for signs so that they may be uniform across the country. These were, after all, recommendations. The only “must” in the manual was the shape and design of the new markers for the United States highway system. This was the shape of the shield, with the name of the state above a line horizontally between the two curves of the sign, and the letters “U S” and the number below that line. These recommendations stated that state road markers should be round.

This was one of the few exceptions in the way signs were designed. People also ask why railroad crossing warning signs are round. The original idea was that the more dangerous a situation is, the more sides a sign would have. It was determined, especially with the number of trains running throughout the United States at the time, that railroad crossings were the most dangerous traffic situation. Round signs have, technically, 360 sides. Cross bucks, the “X” shaped signs at the crossings themselves, have 12 sides.

Indiana changed their state road markers at the time to be more cost effective (this might stem from the fact that they had to create a massive number of such signs for installation on 1 October 1926), removing the words “STATE ROAD,” but keeping the shape of the state on a rectangular sign. The new maps of Indiana issued by the State Highway Commission showed US routes with the new US markers, with regular state roads just numbers like before.

In 1927, AASHO created the first “Manual and Specifications for the Manufacture and Display and Erection of U.S. Standard road markers and signs” for use on rural highways. This created a stronger recommendation for states to use a round sign to mark their state roads. While the MUTCD would be followed for the most part, states still used a state marker that they decided on their own to use.

This was to be followed by the National Conference on Street and Highway Safety issuing an “urban manual” in 1930. Some of the signs matched those in the 1927 manual. But there were conflicts between the two.

The Indiana State Highway Commission started using round markers for state roads on maps in 1930.

Finally, these conflicts were resolved with the AASHO creation of the “Manual of Uniform Traffic Control Devices (MUTCD)” in 1935. Again, it was strongly recommended that state route markers by round. And, again, most states ignored that recommendation.

In the late 1940’s/early 1950’s, Indiana changed the state route markers to be even more cost effective than before. The became square with the state name at the top. These were flat painted signs, as opposed to the embossed (pressed) signs that were in use before. (US Markers were also embossed up to that point.)

So the answer to the subject question is this: the markers on the maps are MUTCD standard, the markers on the roads are not.

As an aside, the MUTCD for many years recommended that urban street signs be green with white letters. Indianapolis, for many years, had black on white street signs. Until the 1970s, they were embossed. In the mid 1970s, they were replaced with bigger flat signs, still black on white. It wasn’t until the late 20th century that Indianapolis started changing to white on green. Other cities that I have been to, such as Cleveland, Pittsburgh, and Norfolk (Virginia) have white on blue. Pittsburgh’s street signs have helped contribute the new standard used today: signs now have lower case letters on the street name legend.

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