The directive is the result of a 13-year-old study, The (Cleveland) Plain Dealer reports. The Pennsylvania Transportation Institute at Penn State found in 1997 that signs entirely in capital letters -- the standard practice for highway signs -- are more difficult for the elderly to understand.
The FHA released an 816-page Manual on Uniform Traffic Control Devices in December. The manual requires states to make signs more reflective by 2018 and to change them to upper and lower case but no deadline was set.
"The reason for these and other changes is to improve safety," Cathy St. Denis, an FHA spokeswoman, told The Plain Dealer in an e-mail. "Signs that are easier to read will help us make roads and the people who drive on them safer."