R 408.42230 Letter style and size.

Rule 2230. (1) A letter shall be block style and upper case for the top panel and upper or upper and lower case for the bottom panel. Letters and numbers shall be legible. (2) Letter size shall be determined by the length of the message and the maximum visibility and readability. Table 2 shall be used as a guide for the minimum letter height at a safe viewing distance. (a) The spacing of letters and words shall not reduce legibility. (b) The height of a letter that is more than 5 inches (125 millimeters) high shall be increased by an additional 1 inch (25 millimeters) for each 35 feet (10.5 meters) of viewing distance. (3) Table 2 reads as follows: MINIMUM HEIGHT OF LETTERS VIEWING DISTANCE Inches Millimeters Feet Meters 5 125 201 - 250 60.3 - 75 4 1/2 113 151 - 200 45.3 - 60 4 100 121 - 150 36.3 - 45 3 1/2 88 106 - 120 31.8 - 36 3 75 91 - 105 27.3 - 31.5 2 1/2 63 76 - 90 22.8 - 27 2 50 61 - 75 18.3 - 22.5 1 1/2 38 41 - 60 12.3 - 18 1 25 31 - 40 9.3 - 12 3/4 19 21 - 30 6.3 - 9 1/2 13 10 - 20 3 - 6 1/4 6 Less than 10 3