The most important factor of LED signage is viewing distance. If your sign will be viewed from long distance by people in the car driving fast then you need a big character size to make it readable. As a rule of tomb you need at least two inch of character height for each 100ft of viewing distance to make it readable. For full-color sign with image and video support you may need bigger size to make better imapct on viewer.
||Minimum Viewing Distance
||Best Viewing Distance