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 CMOS 7.89, “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, hyphens should be added only if doing so will prevent a misreading or otherwise significantly aid comprehension.” You will find in the table at 7.89 that adjectives formed with century are hyphenated; nouns are left open; for phrases like “car rental agency,” the writer can be the judge.