Bill de Blasio has appointed US DOT Under Secretary for Policy Polly Trottenberg to lead the New York City Department of Transportation. Trottenberg is a veteran federal policy maker, whose resume includes stints working for New York Senator Daniel Patrick Moynihan on the 1998 federal transportation bill and for Senator Chuck Schumer.

At the Obama DOT, she’s been an architect of TIGER, the grant program that’s helped fill funding gaps for many multi-modal projects. She was also a proponent of giving official recognition to the progressive street design guidelines produced by the National Association of City Transportation Officials, which until recently was led by outgoing NYC DOT Commissioner Janette Sadik-Khan.

Trottenberg’s policy credentials are top-notch, and advocates including Transportation Alternatives and the Straphangers Campaign greeted news of her appointment enthusiastically. The big question is how her deep experience at the federal level will translate to the rough and tumble of redesigning NYC streets.

There was one off-note at the presser today, when Trottenberg said DOT would be “more collaborative with local communities” on pedestrian plazas. (Could any DOT program be more collaborative than the plaza program?) But in most respects the message from the de Blasio team was one of continued progress on transit, bicycling, and walking.

In a statement, the de Blasio transition emphasized Trottenberg’s mandate to implement a robust Bus Rapid Transit network and improve street safety:

Polly Trottenberg, current Under Secretary for Policy at the U.S. Department of Transportation, will serve as the Transportation Commissioner, executing Mayor-Elect de Blasio’s ambitious agenda to expand Bus Rapid Transit in the outer boroughs, reduce traffic fatalities, increase bicycling, and boost the efficiency of city streets.

“One life lost on our streets is too many. We are committed to the maxim that safety — for everyone who uses the roads, including pedestrians and cyclists — is our top priority,” said incoming Transportation Commissioner Polly Trottenberg. “From improving our roads, bridges and waterways to better serve our citizens and businesses, to connecting New Yorkers to jobs and opportunities through improved high-speed bus service, to expanding biking across the five boroughs, we can have a transportation system that is safe, efficient and accessible to all.”

When Trottenberg was first appointed to a top post alongside Ray LaHood at US DOT, advocates took it as a sign that the Obama administration was serious about transportation reform after all, since the LaHood pick was inscrutable on its own. In New York, her knowledge of the federal bureaucracy and funding landscape should be valuable (for starters, maybe she can place a phone call to fix this problem). But running an implementation agency like NYC DOT, which boils down in large part to the allocation of space, is a very different job than working the levers of federal policy, which is mainly about the allocation of money.

De Blasio has set ambitious goals for streets and transportation policy. Achieving them will be tough, and important decisions will inevitably come down to not just the DOT commissioner, but also deputy mayors and de Blasio himself. An early sign that his administration intends to stick to its transportation targets will be if the talented people who’ve risen through the ranks at NYC DOT during Sadik-Khan’s tenure stick with the agency under Trottenberg.

While this marks the end of Sadik-Khan’s remarkable leadership of NYC DOT, it hopefully represents a continuation of the spirit of innovation and determination that she brought to the job. Check here tomorrow morning for Streetsblog’s thoughts on Sadik-Khan’s legacy and accomplishments.