Electronic Displays

The physical size of the electronic displays is the idea most people start out with. This is not the correct first step. Instead, determine the viewing distance of the electronic displays or the distance from where you want the majority of the audience to read your message. As a general rule of thumb for electronic displays, one inch character is viewable from up to 50 feet away. The traffic pattern in front of the sign needs to be taken into consideration as well. A driver will have less time to read a message than a pedestrian walking. On average, the typical audience will need at least 3 to 4 seconds to read about 6 to 8 groupings of text and/or graphics on your electronic displays.
ISA, International Sign Association