Better Lettering Means More Visible Street Signs

After accepting more than 40 years of traditional road and street signage, the Federal Highway Administration (FHA) now relies on newer guidelines, which are outlined in the Manual on Uniform Traffic Control Devices (MUTCD). Some of the recent changes are responses to a 1997 study titled ‘The Effects of Font and Capitalization on Legibility of Guide Signs.’ The project was conducted at the Pennsylvania Transportation Institute Bus Research and Testing Facility and at Pennsylvania State University.

Two groups of 12 licensed senior citizens became the subjects for both day and night objective testing. Older adults were chosen for this study because of expressed concern for the reduced acuity of aging drivers and the ever-increasing numbers of seniors driving on the roads and streets of the United States.

The project addressed two road-sign issues: the font size and style of the lettering and the effectiveness of mixing uppercase and lowercase lettering. Older signs generally followed a wide-stroke format and used all capital letters. The traditional broad stroke against a bright background often caused ‘visual bleed-through’ into spacing, a phenomenon that resulted in blurred word recognition and reduced legibility.

For this project, a Clearview and a Clearview Condensed font, both with wider spacing between letters and taller, narrower letter strokes, were substituted on signs that contained three test words. Mixed-case lettering was also used. The variable in the study was the threshold distance necessary for word recognition. Participants were required to identify a target word by its location at the top, the middle or the bottom of the sign.

The results of this study demonstrated that visibility could be improved by redesigning the shape and spacing of the lettering on traffic signs. Participants scored a significant 16 percent improvement in night-time visibility when tested. Improvement in reading distance for mixed-case words seemed to be related to how well the words were already-known or expected.

In 2009, the FHA issued the following new road signage guidelines:

  • For post-mounted street name signs, the initial uppercase letters should be a minimum of 6 inches high, and the lower case letters should be at least 4.5 inches high.
  • For multi-lane streets on which traffic travels faster than 40 miles per hour, uppercase lettering should be a minimum of 8 inches high, and lowercase letters should be at least 6 inches tall.
  • Overhead traffic signage should have uppercase letters that are a minimum of 12 inches tall and lowercase letters that are at least 9 inches tall.
  • Local roads with speeds below 25 miles per hour can display road signs on which the uppercase lettering is at least 4 inches tall and the lowercase letters are at least 3 inches tall.
  • The lettering for the words ‘street,’ ‘road’ and ‘avenue’ must be at least 3 inches high.
  • No longer are words that are all uppercase allowed.

By improving their road signage, cities and municipalities can promote driver safety through reducing potential accidents. Emergency response time is expedited. Congestion is reduced, and traffic flow can be enhanced. As directional recognition and response time are shortened, roads become safer and more efficient. Not only senior citizens but the driving population as a whole is being positively impacted by these important changes.

Traffic Law