Smoking and soda bans aside, the reshaping of New York City’s streets has been among the most controversial hallmarks of Mayor Michael Bloomberg’s three terms in office. But the bike lanes and concrete planters championed by Bloomberg were in fact the brainchild of his transportation commissioner, Janette Sadik-Khan. Along with the mayor, Sadik-Khan will leave City Hall at the end of this month, leaving behind a vast legacy of progressive transportation improvements that have altered the city’s streetscape more profoundly than any administration in at least the last 50 years. Sadik-Khan recently sat down with a handful of politicians, architects and planners at the Center for Architecture to assess six years’ worth of changes and speculate about what this city’s streets need next.

“Nothing happens in New York without vigorous conversation and some degree of contention,” says Sadik-Khan. For her, contention has come in no small dose. When painted plazas began popping up in roadways throughout the city in 2007, Sadik-Khan and her department were accused of ruthlessly pushing through a pet project without consulting neighbors. In 2011, onetime mayoral frontrunner Anthony Weiner apparently told Bloomberg his first act in office would be to “tear out your fucking bike lanes.” Well, Weiner was later spotted pedaling down a lane himself, and Sadik-Khan has steadfastly defended the plaza program as democratic – the department hosts 2,000 local community meetings per year.

In six years, the city’s Department of Transportation has created 59 new public spaces out of traffic lanes, handing a total of 39 acres of space over to pedestrians. Many of these have been so-called “overnight” plazas that make use of paint, planters and granite blocks to reclaim pedestrian space virtually overnight so that behaviors and attitudes can be observed and debated before refinements are made to more permanent installations. This model has been duplicated in Los Angeles, Philadelphia and Mexico City. Bloomberg boasts that since the plaza program was introduced to Times Square in 2009, retail rents in the area have more than doubled. Now, with the help of Norwegian design firm Snøhetta, the city is converting the pedestrian mall along Broadway into a permanent fixture. In a survey, 72% of New Yorkers said they like the plazas.

Noting that pedestrians were brazenly dodging car and bike traffic to cross the street in a section of Midtown, DOT installed mid-block crosswalks to link several pedestrian alleys from 51st Street to 57th Street between 6th and 7th avenues. They called it 6½ Avenue. This pedestrian-first approach to jaywalking is worlds away from a plan cooked up by Mayor Rudy Giuliani in the 1990s to install Jersey barriers on midblock sidewalks, effectively caging in frisky pedestrians. Still, pedestrian inattention is the second-leading cause of accidents in the city. To gain the attention of daydreaming pedestrians, DOT began painting big “LOOK!” signs in busy crosswalks, with eyes in the ‘O’s glancing in the direction of oncoming traffic.

Some of the changes, like new bike lanes, weren’t revolutionary at all, but were nevertheless decried by a vocal minority. In 2011, former transportation commissioner Iris Weinshall was part of a lawsuit challenging a newly installed bike lane on tony Prospect Park West, where she lives with her husband, US Senator Chuck Schumer. Despite being ostensibly pro-bike lane (she installed a number in her own time in office), Weinshall took issue with the DOT’s contention that speeding and accidents had fallen considerably after the lane was installed. Bloomberg, who made his billions by selling valuable data, has long instructed his staffers, “in God we trust. Everyone else, bring data.” Sadik-Khan’s data are unequivocal. Fully 64% of New Yorkers polled said they support the expansion of bike lanes – surprising since opponents have been so outspoken. Sadik-Khan declared that the people are “way ahead” of the politicians and the press.

DOT has installed 350 miles of bicycle routes since 2007, bringing the total to 573 (enough to bike to Columbus, Ohio) and reached its goal of doubling bike commuting in five years one year early. Bike deaths are down despite the surge in cycling, suggesting there is safety in numbers. The expansion in cycling to a wide population beyond “kamikaze bike messengers” owes a huge debt to the rollout of Citi Bike this past summer. Citi Bike has experienced the fastest subscriber growth rate of any bike share program in the world, and the department receives dozens of requests from communities asking for an expansion of Citi Bike to their neighborhoods.

But Sadik-Khan is insistent that DOT’s bike and pedestrian initiatives have not come at the expense of auto traffic. Auto traffic entering Manhattan below 59th Street has fallen 6.5% since 2003, in part because recent population and economic growth has relied more on public transit than auto use. Also, a new program called Midtown in Motion adjusts Midtown traffic signals in real time using microwave sensors, video cameras and E-ZPass readers at 23 intersections, leading to a 10% improvement in travel times. A smart parking system helps drivers locate parking spots with their phones and adjusts prices based on demand, helping increase turnover and reduce congestion stemming from spot-hunting.

Annual traffic fatalities are down 61% from 1990 to 2012, to their lowest levels on record. Since 2004, annual traffic deaths have been lower than 1910 levels, when the city had just half today’s population. DOT has successfully persuaded the New York State Legislature to expand the red light camera program six times since 1991. But today there are just 190 red light cameras, making up less than 2% of the total number of signalized intersections in the city. In pushing for more, the city has encountered resistance from Albany, where legislators are stymied by privacy concerns.Despite a frequently adversarial culture between motorists, cyclists and pedestrians, most New Yorkers, at one time or another, are all three. We are frustrated by cyclists when we are in cars, and frustrated by drivers when we’re walking. In the transportation planning jargon, “complete streets” aim to harmoniously balance use by buses, cyclists, pedestrians and motorists. Whether Sadik-Khan and her department have been successful at achieving this balance is up for debate but one thing is clear: they have proved they are serious about working toward that goal.

For all their street savvy, New Yorkers can be awfully stubborn about change, especially changes seen as coming from outside. But Sadik-Khan is part of a cohort of urban designers who believe that handsome, dynamic streets will play an ever-increasing role in attracting the kinds of people and companies so crucial to the 21st century economy. A new generation of New Yorkers thinks bus lanes, plazas, and bike lanes are the norm, which certainly wasn’t always the case. “Salmoning” and “street-calming” have entered the vocabulary, Sadik-Khan crows.

We don’t yet know whom incoming mayor Bill de Blasio will appoint as his transportation commissioner, but the new administration is unlikely to be quite as forward-thinking and world city-building as the current one. De Blasio was opposed to the Prospect Park West bike lane and the failed congestion pricing scheme that would charge all drivers a fee to enter Manhattan below 59th Street. He is an avid motorist. But as Brad Lander, the City Council Member representing Cobble Hill and Park Slope, has said, de Blasio has come a long way on these issues because “he listens to people and sees how things are working.” If he is open to suggestions, there’s no shortage of New Yorkers with some pretty radical transportation ideas. Still, congestion pricing is probably not in the cards for de Blasio’s first 100 days.