If a State has a practice of erecting on projects under actual construction without Federal-aid highway assistance signs which indicate the source or sources of any funds used to carry out such projects, such State shall erect on all projects under actual construction with any funds made available out of the Highway Trust Fund (other than the Mass Transit Account) signs which are visible to highway users and which indicate each governmental source of funds being used to carry out such federally assisted projects and the amount of funds being made available by each such source.