Calculations based on externally (or naturally) lit sign with all upper case Helvetica letters utilizing optimal negative space. Factors that may affect required letter size are: color scheme, font selection, traffic and weather conditions, or sign standoff. Consult with experienced sign professionals at Gemini Signs for optimal design.
This letter visibility chart has been made based upon information provided by Pennsylvania Transportation Institute, Penn State University and the United States Sign Council (USSC). c1998.