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We are no longer accepting questions about transportation. Read the first and second sets of answers.

Why do subway trains open only a few doors in some stations? What are those art-deco ventilation towers above the Holland Tunnel? What is the fastest route from Prospect Heights to Kennedy Airport? Why is there no subway to Staten Island?

Transportation in New York City is at once universal and mysterious: a familiar, well-worn labyrinth with an encyclopedia’s worth of idiosyncratic tendencies and tidbits. Next week on City Room, we will be opening the digital floor to questions about anything that moves in the five boroughs, from yachts and helicopters to defunct subway trains and long-lost rail routes.

Michael M. Grynbaum, guest blogger and former transportation reporter at The Times, will moderate, and we will be calling on a host of regional experts, transit executives and local historians to lend their knowledge to the discussion.

Submit your questions below in the comments. We will choose the best ones and start posting answers early next week.