I spent a lot of time when driving (and I have done a lot of driving in the last two weeks) looking at signs. A great deal of them momentarily confuse me as they can be interpreted several different ways.
For example, on a fast food restaurant, “FOUR MEALS FOR UNDER 4.” Does this mean:
a) They have four meals, each priced under $4?
b) Four meals are available together for a price less than $4?
c) They have four meals for those under 4 years of age?
The answer is almost certainly a), but how do I know that? Genre. I know fast food restaurants group foods together in meals for a flat rate, and $4 seems rather low for four meals, unless they consisted of frozen bean burritos. However, it does seem possible that they might be launching new meals aimed at children, but 4 years old seems an odd cutoff date, and there is no ‘those’ or ‘children’ after ‘for’, giving the preposition a easily discernible object. Likewise, ‘FOUR MEALS, EACH PRICED UNDER $4’ or ‘FOUR MEALS TOGETHER FOR UNDER $4’ would help.
Even simpler signs are also potentially ambiguous. ‘SPEED LIMIT 35’ might seem straightforward with its implied ‘THE SPEED LIMIT IS 35 MILE PER HOUR’. But what if the verb is not a dropped IS, but SPEED, an imperative? Then there appears to be a limit to how many vehicles can speed, which is 35, or, perhaps, that you are required to speed, but can go not faster than 35. Some speed limit signs helpfully post both a minimum and a maximum speed – ‘SPEED LIMIT 55 MINIMUM 45’ or delineate by type of vehicle, as in ‘SPEED LIMIT 65 TRUCKS 55,’ but either way, there is a lot of verb reduction. ‘THE SPEED LIMIT IS 55 MILES PER HOUR AND THE MINIMUM SPEED IS 45 MILES PER HOUR’ requires a rather large sign to be readable at speed, but the compression leads to ambiguity. Note I’ve assumed MPH rather than KPH.
What about the ultimate compression in road signage, STOP? Is this an imperative that means ‘STOP IMMEDIATELY’ (the adverb makes it clear STOP is a verb) or an noun that simply exists (‘A STOP IS HERE’)? There are such stops, and there noun-ness is confirmed by adjective use (BUS STOP), although BUS can be a noun itself, making STOP again an imperative. Since buses do stop at bus stops, the sign can handle either interpretation.