Now, just 12 years later, the FHWA is reversing itself: "After more than a decade of analysis, we learned—among other things—that Clearview actually compromises the legibility of signs in negative-contrast color orientations, such as those with black letters on white or yellow backgrounds like Speed Limit and Warning signs," said Doug Hecox, a FHWA spokesperson, in an email. The FHWA has not yet provided any research on Clearview that disproves the early claims about the font's benefits. But there is at least one factor that clearly distinguishes it from Highway Gothic: cost. Jurisdictions that adopt Clearview must purchase a standard license for type, a one-time charge of between $175 (for one font) and $795 (for the full 13-font typeface family) and up, depending on the number of workstations.
That doesn't seems like a very good use of tax money, for something that can be nondestructively reused once created.