According to the FHWA website, Clearview 6-W is an equivalent to FHWA Series F. However, the ClearviewHwy website disagrees, stating that Clearview 6-W has no FHWA equivalent. Which is true? Series F isn't very commonly used, so perhaps there was no need to develop an equivalent for it.
It's an equivalent in the sense that it's the widest variant of Clearview offered. However, IIRC, the x-W fonts are actually slightly narrower than the equivalent Series X fonts, to compromise the fact that white numerals have the optical illusion of appearing wider than they really are. So, the actual equivalent to Series F would be Clearview 6-B. Again, as far as the font families go.