Air quality improved 22% in Manhattan congestion pricing zone, modest improvement in region, study finds

Particle pollution in New York City decreased significantly since congestion pricing tolls went into effect in January, researchers at Cornell University found — a result that proponents cited as a significant success for the program.

The effects were found not just within the congestion zone below 60th Street, but in all five boroughs and, to a lesser extent, in the surrounding metropolitan region.

"As other American cities consider similar policies," authors wrote, "our findings demonstrate that cordon pricing can deliver rapid, geographically broad environmental benefits."

New York City was the first U.S. city to introduce tolls to reduce gridlock and air pollution, a strategy that has been implemented in London, Milan, Stockholm and Singapore. The rules went into effect in January 2024 after decades of study and in spite of vigorous opposition from officials in suburban New Jersey and Long Island. Opponents have argued that the toll — $9 for most vehicles driving in the zone during peak hours — would add an additional expense for a region struggling with its high cost of living.

The researchers, who are in the systems engineering program and the School of Civil and Environmental Engineering at Cornell, wanted to know if levels of fine particulate matter (or PM2.5) would fall as drivers avoided the tolled zone.

PM2.5 — so called because the particles measure 2.5 micrometers or less, 30 times smaller than a human hair — are so tiny that they can pass through the lungs and into the bloodstream, where they can migrate throughout the body. Long-term exposure is linked to many diseases, from lung cancer to Alzheimer's disease, according to the World Health Organization.

The researchers collected data from six air quality monitors in the congestion relief zone, 23 more in upper Manhattan and the outer boroughs, and 13 north of the city, in New Jersey and on Long Island.

Their results, published Monday in the journal Nature, found that within the congestion relief zone, average daily maximum PM2.5 levels declined by just over 3 micrograms per cubic meter from January to June 2024 — a reduction of 22%. The figures are based on models of where levels would be without a toll policy.

The effects in the outer boroughs and the wider metropolitan area were "more modest" but still statistically significant, the authors wrote. Particle pollution levels were reduced on average by 1.7 micrograms per cubic meter in the five boroughs, and in the wider metropolitan area by .7 micrograms per cubic meter.

The improvements in the outer boroughs was a surprise. Environmental impact studies suggested that the tolls would divert traffic, particularly trucks, from Manhattan to surrounding areas, especially the South Bronx, where neighborhoods were already burdened by heavy truck traffic, industrial facilities and poor air quality.

Kevin Garcia, senior transportation planner at NYC Environmental Justice Alliance, recalled he was dismayed by those findings. His group had advocated for congestion pricing for years, but "what we didn't want to see was the Bronx or any community to become a sacrifice zone for the congestion pricing program," he said.

As it turned out, that expected increase in traffic hasn't happened. There are now fewer cars driving on the roads across the city, not just into lower Manhattan. A study by the Regional Plan Association found drivers spent 25% less time crawling through Manhattan streets after the tolling began and 9% less time in traffic jams in the outer boroughs and parts of New Jersey.

"To all the naysayers, the doomsday tellers, saying this would be the demise of New York City," Gov. Kathy Hochul said at a press event Thursday, "I am so proud that as we are approaching the one-year anniversary ... it has been wildly successful." Since the program began, 20 million fewer cars have entered the city below 60th Street, Hochul said. For those who do drive, she added, "coming from Long Island and the Hudson Valley, your ride is faster."

The tolls are expected to raise $500 million by the end of the year for the MTA — 10% of which will be directed to infrastructure improvements for the LIRR. 

The authors of the Cornell study said their results show that congestion pricing can be "a rare intervention" that promotes several goals together, both ecological and economic: reducing pollution, reducing gridlock, and generating funds for public transportation improvements.

Check back for updates on this developing story.