Second language is added as a
module to the bottom of a sign.
Too many languages make it hard
|The ANSI Z535.2 sign standard uses a ratio of 25 feet of viewing distance per inch of text height, assuming favorable viewing conditions.|
|For unfavorable viewing conditions, this ratio lowers to 12.5 feet of viewing distance per inch of text height. |
|For a more optimistic calculation, the traffic sign 'rule-of-thumb' is 50 feet per|
|inch of text height.|
This question has been studied by several researchers. The answer depends, generally, upon the complexity of the underlying graphic. If, for example, the graphic has a great deal of detail that would be obscured by a diagonal red over-slash, the slash could be placed underneath the black symbol. In the example above, the slash is best shown underneath the black graphic (the version on the right). In this example you can see the operator's hands and how he uses his legs and weight to drive the shovel into the ground. Adding these details make the digging metaphor much clearer.
For more information, see Dr. Wogalter's study, "Pictorial Negations: Preferences for Different Circle Slash Variations" or R.E. Dewar's study, "The Slash Obscures the Symbol on Prohibitive Traffic Signs", Human Factors, 18, 253-258.
The upper case alphabet has many more straight lines and is far simpler. A well-know typography expert once stated, "capital letters are for tombstones only!"
It is far better to put the sign on the outside. That way the sign is most easily seen and read. With a strong fastening system, the sign is very hard to steal – even for professional scrap metal vandals. A sign on the inside of the fence is not as effective.