Thanks to Twitter pal Joanne (@jm_ingram) for sharing this deliciously botched sign all the way from Beantown. Her take:
"Smoking isn't allowed in Boston cab's, but bad grammar is just fine."
Indeed, Joanne. And how about those Red Sox ...
For the thousandth time, please repeat the AP Stylebook's rule: No plurals from apostrophes except when dealing with abbreviations containing two or more internal periods (e.g. Ph.D.'s).
Beyond the obvious problem, Joanne's picture offers Mr. Rewrite the opportunity note that the correct term for the state of Boston cabs is smoke-free, not smokefree. The AP Stylebook has no entry on this term, though there is a new entry calling for tax-free. There's also no entry in Webster's New World College Dictionary, where one turns for matters not covered by the stylebook, and that means smoke and free are independent terms that create a compound modifier.
Why is smoke-free hyphenated after the noun? Per the AP Stylebook, many compound modifiers that are hyphenated before a noun aren't hyphenated after. But for clarity retain the hyphen if the modifier follows a form of the verb to be. That's the case here.