Hyphens, En Dashes, Em Dashes

Q. Is it necessary to hyphenate “car-rental agency,” or is “car rental agency” clear enough? Also, the same question as it applies to “16th-century ornamental bridge.” Sometimes, I think writing has gone hyphen-crazy.

A. As we say at 7.85, “In general, Chicago prefers a spare hyphenation style: if no suitable example or analogy can be found either in this section or in the dictionary, hyphenate only if doing so will aid readability.” You will find at CMOS 7.85 that adjectives formed with century are hyphenated; nouns are left open; for phrases like “car rental agency,” the writer can judge.