According to: http://www.fhwa.dot.gov/interstate/faq.htm http://www.fhwa.dot.gov/interstate/faq.htm "the National Highway System Designation Act of 1995 prohi

According to: http://www.fhwa.dot.gov/interstate/faq.htm http://www.fhwa.dot.gov/interstate/faq.htm "the National Highway System Designation Act of 1995 prohibited the use of Federal-aid highway funds to convert existing signs or purchase new signs with metric units." It appears from my reading of the law that the prohibition expired in 2000.