Height
Now that you know where your sign will be placed and how large it needs to be the next question is how tall the sign needs to be. The further away the sign will be read, and the further it is from the road, the taller the sign must be to be visible from a car. Freeway signs intended to be read from great distances should be very tall; signs located in a business district with 30 mph traffic only need to be tall enough that parked and moving vehicles will not block them from view.
Although the length and content of a sign’s message generally dictates the overall sign dimensions, Table 5 sets out generally accepted sign height guidelines. They assume that the sign is mounted perpendicular to the roadway, that the size of the letters meets the minimum size standards listed in Table 4, and that the sign is mounted within 5-10 feet of the nearest edge of the public right-of-way. Note that although the table lists heights measured to the top of the sign face, the height from the ground to the bottom of the face should always measure a minimum of 7 feet so the sign is not blocked from view by passing or parked vehicles.
| Speed Limit |
Number of Traffic Lanes |
Sign Height (to top of sign face) |
| 25 mph |
2 |
12 feet |
| 25 mph |
4 |
12 feet |
| 35 mph |
2 |
20 feet |
| 35 mph |
4 |
20 feet |
| 45 mph |
2 |
35 feet |
| 45 mph |
4 |
35 feet |
| 55 mph |
2 |
50 feet |
| 55 mph |
4 |
50 feet |
| Urban Freeway |
N/A |
75 feet |
[2] Richard N. Schwab entitled Safety and Human Factors: Design Considerations for On-Premise Commercial Signs, cosponsored and published by The Signage Foundation for Communication Excellence Inc. and the International Sign Association (1998).
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