“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.)