The Federal Highway Administration is requiring that new street signs comply with updated standards to use mixed case Clearview.
Mixed-font Clearview was readable from roughly 440 feet away, whereas typical all-cap lettering was readable only at a distance of 384 feet. By expanding the interior spaces of certain letters, Clearview also reduced halanation—the process by which letters blur together late at night. In darkness Clearview became readable at 387 feet, against 331 for the standard highway font style.
More about this here.