Federal copy editors are demanding the city change its 250,900 street signs — such as these for Perry Avenue in The Bronx — from the all-caps style used for more than a century to ones that capitalize only the first letters.

Changing BROADWAY to Broadway will save lives, the Federal Highway Administration contends in its updated Manual on Uniform Traffic Control Devices, citing improved readability.

At $110 per sign, it will also cost the state $27.6 million, city officials said.