In Bloomberg’s City of Bike Lanes, Data Show, Cabs Gain a Little Speed

But according to the New York City Transportation Department, a lengthy campaign to reallocate street space for cyclists and pedestrians has produced a curious result: If anything, officials said, cars are moving more quickly in the city’s most congested areas.

Citing GPS data from the city’s yellow cabs, the Bloomberg administration said that average traffic speeds in Manhattan’s primary central business district, south of 60th Street, had increased nearly 7 percent since 2008.

And it is not as though the streets have become less congested: traffic volume has remained relatively level in recent years, as transit ridership and bike commuting have increased. In 2008, about 756,000 cars entered Manhattan south of 60th Street each day, transportation officials said. In 2011, the most recent year for which full data is available, the figure was 764,000.

“We’re not, despite our reputation, trying to take from one and give to the other,” Bruce Schaller, the department’s deputy commissioner for traffic and planning, said. “It isn’t a zero-sum game.”

The most recent speed data, part of an annual report known as the Sustainable Streets Index, was calculated using taxi trip logs, drawing on the distance and duration of a trip, including time spent stopped in traffic or at lights. The report also includes a section on taxi driver behavior in the rain — cabbies, happily, were found to drive 11.9 percent slower on days with at least an inch of precipitation — and an appraisal of the city’s bike-share program, which has attracted more than 75,000 annual members.

As it has in the past, the study also examined how the calendar might affect traffic speeds in Manhattan. January, February, March and August were the fastest months; May, June, July and December were the slowest, with one caveat: The fastest average speed, 14.8 miles per hour, was recorded on Christmas Day. The analysis excluded days during and immediately after Hurricane Sandy.

The city has observed speed fluctuations in past years, officials said, but a flagging economy, service cuts on subways and buses, and increases in transit fares had made it difficult to tease out long-term trends.

Janette Sadik-Khan, the city’s transportation commissioner, said that with more comprehensive post-recession data now available, the department could say with confidence that traffic speeds had at least remained stable after the introduction of pedestrian plazas and hundreds of miles of bike lanes. (If 2009 is used as a comparison instead of 2008, traffic speeds have increased 0.3 percent as traffic volumes remained roughly flat.)

Critics of the Transportation Department, including some local officials, have in the past accused the city of selectively using data to bolster its claims about improving the streets. And among drivers, the department’s most recent conclusions were met with nearly universal distrust.

“They cut the streets in half to have people sit,” said Abdullah Muhammed, a general contractor, sitting in his truck near 49th Street and Broadway on Tuesday.

Asked if this had made navigating Midtown more difficult, Mr. Muhammed gave a lengthy smirk, then nodded toward a clogged portion of Broadway.

Christopher McBride, a transportation specialist with AAA New York, noted that while traffic volumes had been fairly consistent in recent years, they had decreased significantly compared with 10 to 15 years ago, suggesting that some commuters had simply given up on Midtown driving in the Bloomberg years.

“It is more of a hassle now than ever to drive into the central business district,” he said. “Some of these changes that have occurred, they’re more intimidating for drivers. And a lot of parking has been eliminated.”

He added improvements in the city’s traffic signal system had offset the “negative traffic speed impacts of pedestrian plazas and bike lanes,” allowing speeds to at least remain steady.

The city’s report does not discuss how certain projects, like the closing of several blocks along Broadway, have affected speeds in their immediate surroundings, though a 2010 study found that travel speeds near the plaza had improved. A separate report released that year from New York City Transit suggested that the plazas of Times and Herald Squares had slowed some buses as traffic was rerouted onto Seventh Avenue.

But Mr. Schaller argued that additions like protected bike lanes were not especially disruptive to drivers. “When we put in a bike lane, you think, ‘Oh, you’re taking a lane,’ ” Mr. Schaller said. “But that left curb was always taken by the left-turning cars anyway. And the through traffic has the same number of lanes that it did before.”

In his final years in office, Mr. Bloomberg has at times taken great pains to slow down the city’s drivers. He pushed for a measure, recently enacted, to install speed-tracking cameras near some city schools, and has introduced designated “slow zones” where the speed limit is reduced to 20 miles per hour, from 30 m.p.h.

But drivers in much of Manhattan can rarely flout the law, even if they try. The average taxi speed south of 60th Street was 9.3 miles per hour, the report said, leaving passengers behind the pace of a well-trained runner.