(CNN) When the city of Ames, Iowa, installed rainbow-colored crosswalks at a downtown intersection, it wanted to signal that it was welcoming and inclusive to people of all gender identities, sexualities and races.

So when the federal government threw the city a roadblock, they decided to ignore it.

In a letter dated September 5, the Federal Highway Administration (FHWA), a division of the US Department of Transportation, requested that the colorful crosswalks be removed because they didn't comply with federal traffic control standards.

The city of Ames, Iowa, introduced new, inclusive crosswalks at the intersection of Fifth Street and Douglas Avenue on September 4.

According to federal rules, crosswalks can only use white paint.

"Crosswalk art has a potential to compromise pedestrian and motorist safety by interfering with, detracting from, or obscuring official traffic control devices. The art can also encourage road users, especially bicycles and pedestrians, to directly participate in the design, loiter in the street, or give reason to not vacate the street in an expedient or predictable manner," the FHWA wrote in a letter to Ames City Manager Steve Schainker.

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