Why Chicago Street Signs were changed from Black on Yellow to White on Green.

The U.S. Department of Transportation's "Manual on Uniform Traffic Control Devices" (MUTCD) is a constantly evolving guidebook showing cities the standard in street signage since 1935.

In the 1970s, the MUTCD began a national effort to help foreign visitors navigate the United States by adopting a color-coded sign system similar to Europe's. Chicago adopted the white-on-green street signs as part of that effort in 1975.

Many Chicagoans remember the yellow street signs that Chicago used.

The MUTCD's revised guidelines restricted yellow in signage to warning signs. It also mandated white backgrounds with black and red lettering or symbols for use as regulatory signs (for instance, "No U-Turn" signs were replaced with a black U with a red slash on a white background).

The guidelines recommended phasing out words on signs where possible and relying instead on universally understood symbols, like a red circle broken by a white line to indicate "Do Not Enter." Under that scheme, the color symbols for guidance were green and white – so "reflectorized" white-on-green street name signs became the new standard.

No official system was in place during the city's early years, making wayfinding pretty tough in our fast-growing city. A public call for street identification signs began around the turn of the 20th century when street names were often simply painted onto poles at neighborhood corners (if they were indicated at all).

Later, black-and-white or brown-and-white signs appeared
around the city, particularly downtown.

Finally, in 1936, President Franklin Roosevelt approved a grant for Chicago to hang 64,000 black-on-yellow steel street signs as a Public Works Administration project – but those signs didn't stick around very long. Most were removed for metal drives during World War II.

Not long after the war ended, the city began to examine new sign designs, testing out various lettering styles in the Loop. Once a style was settled, Chicago ordered new porcelain-coated steel street signs, again in the black-on-yellow color scheme, beginning in 1950. The signs were installed over the next few years, starting at the city's edges and working their way into the Loop. This time, rather than attaching the signs to the poles with straps that would rust and break, the signs were secured with bolts going into the poles.

When Chicago moved to the white-on-green signs in 1975, the Chicago Department of Transportation (CDOT) again gradually installed thousands of signs throughout the city's more than 800 streets. But this time, the city had the brilliant idea of selling the beloved yellow signs to residents, so occasionally, you'll see a yellow sign decorating a home or business.

In my personal collection, West Arthur Avenue is the street I grew up on.

In 2009, the Federal Highway Administration announced in its MUTCD that all cities should use the upper and lowercase format for their street signs because upper/lowercase words are easier to read than all uppercase. 

According to research performed by the Pennsylvania Transportation Institute, people read all-uppercase words one letter at a time but recognize upper/lowercase formatted words as a whole, making reading "MICHIGAN AVENUE" slower and more complex than reading "Michigan Avenue" while driving past. The upper/lower format also leaves more space around each letter, making the letters easier to distinguish for aging eyes.

Compiled by Dr. Neil Gale, Ph.D.