Earlier today Bill de Blasio settled one of the big questions of the transition period, announcing that he’s going to move into the mayoral residence at Gracie Mansion. Next question: How’s he going to get to work?

Michael Bloomberg, who lives in his Upper East Side townhouse while using Gracie for special events, made a habit of riding the Lexington Avenue express down to City Hall for 12 years, though he gets a 22-block chauffeured escort to the train. De Blasio is a self-described motorist whose morning routine, until now, has involved driving his son Dante from home in Park Slope to high school in Downtown Brooklyn. Taking transit to work would be an adjustment.

Gracie Mansion is not very transit-accessible. It’s all the way by the East River — four and a half long blocks plus two short blocks from the Lexington Avenue express stop at 86th Street. But an invigorating walk to the train would give de Blasio a better feel for pedestrian conditions in the city than most local electeds — who tend to either get driven everywhere or drive themselves around with the guarantee of free parking at the end of every trip, thanks to placards. A mayor who makes walking part of his commute could start each workday with some on-the-ground observation of what it will take to eliminate pedestrian deaths.

When de Blasio has a morning meeting at the governor’s office on 41st and Third, a better option might be the M15 Select Bus Service, which runs downtown on Second Avenue. And taking the M15 home, even if it’s just once a week, would send an even more powerful message than riding the train.