Older font Highway Gothic will not be replaced by newish Clearview as it does not live up to expectations to deliver better legibility in various conditions:
But, it turns out, later research has not backed up this initial belief. It turns out that all that research suggesting the new font might be more legible was more due to the fact that older, worn signs were being replaced with nice, fresh, clean signs which were, naturally, more legible.
An exemplar case when coincidendal relation was confused with consequential.