Air Quality Impacts of Congestion Relief Zone Tolling
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Published on:
August 14, 2026
Key Takeaways
Generally, pollution at all locations held steady or improved slightly. This continues the trend of improving air quality in NYC over the past 20 years. For more long-term trends, see the NYCCAS Annual Report.
Inside the CRZ, pollution decreased slightly or stayed the same in 2025 compared to 2024. Measured pollution levels were not significantly different because of congestion pricing.
At EJ neighborhood sites, congestion pricing didn't increase pollution. This is good news. It didn't worsen air quality near major routes around the CRZ. At one location (BQE) levels of one pollutant didn't improve as much as would be expected in comparison to changes at the control site.
Background
In January 2025, MTA Bridges and Tunnels (MTABT) started charging a toll for vehicles entering the Congestion Relief Zone (CRZ), Manhattan south of and including 60 Street, excluding the Franklin D. Roosevelt (FDR) Drive, the West Side Highway/Route 9A, and the surface roadway portion of the Hugh L. Carey Tunnel connecting to West Street. Congestion Relief Zone tolling, commonly referred to as congestion pricing, was introduced to reduce traffic while raising a reliable source of funding for public transit improvements.
Modeling and analysis from the mandatory federal environmental review for congestion pricing did not predict significant changes in air quality resulting from congestion pricing. Recognizing community concerns, the program sponsors (including MTABT, the New York City Department of Transportation, and the New York State Department of Transportation) committed to monitor and report on air quality. These agencies partnered with the New York City Health Department and Mental Hygiene (the Health Department) to conduct this work. The Health Department expanded its existing air quality monitoring network, the New York City Community Air Survey (NYCCAS), to evaluate the impact of congestion pricing on NYC’s air quality, especially in environmental justice (EJ) communities identified in the Final Environmental Assessment as potentially having increases in truck traffic.
With a full year of data since congestion pricing began, we can now accurately evaluate its effects on air quality. A full year of data means we can better differentiate any impact from other factors that affect air pollution, like changes in wind, temperature, building heating, commercial cooking, construction and industrial activities. Two interim reports, Initial data from Congestion Relief Tolling and the Congestion Relief Zone Tolling First Evaluation Report, noted that the preliminary data suggested air pollution either did not change or continued to decrease as in previous years both within and outside the zone.
Air pollution monitoring
We collect data using two different types of air quality monitors:
Integrated monitors are the gold standard for measuring air quality in ways that are relevant to public health. This type of monitor is the same kind used by the Environmental Protection Agency to monitor air for compliance with the Clean Air Act because it directly measures pollutant mass, whereas other methods only estimate it. It is important for this study that the pollution is measured as accurately as possible.
The monitors are placed in sites designed to reflect long-term neighborhood-level exposures to pollution. Integrated monitors measure four different pollutants: Fine particulate matter (PM2.5), nitrogen dioxide (NO2), nitric oxide (NO), and black carbon (BC). While all these pollutants are produced by vehicles, NO2 is considered the best indicator of traffic-related air pollution exposures. NO2, PM2.5, and BC can all have negative effects on health.
Real-time monitors are placed next to high-traffic roadways and measure PM2.5. They are best at capturing daily patterns, so that we can correlate pollution with traffic levels. However, real-time monitors are more affected by factors like weather and particle size than integrated monitors, so their results are less reliable.
EJ-Designated Community Site Analysis
In consultation with stakeholders, the Health Department increased monitoring in several communities that the Final Environmental Assessment identified as environmental justice communities with the potential for increases in truck traffic. These areas are: Major Deegan Cross Bronx BQE SI Expwy FDR Trans-Manhattan Van Wyck (control)
Click on a site above to learn more about that community.
Evaluation analysis
Here's a guide for interpreting these charts:
The blue dot is the average pollution level, and the gray bar is the Standard Error. The shorter the gray bar, the greater the confidence in the average - the more precise we know our average to be.
The purple dot shows the difference between the observed and projected values after congestion pricing, along with 95% confidence intervals (the purple bar), a statistical measure that shows the range of values that difference could be and still be true. If the confidence interval stretches from negative numbers to positive numbers, then the difference is not significant, meaning there is no change in pollution due to congestion pricing. If the purple bar and dot are entirely on the right or left side of zero (dotted line), then the difference is significantly different from zero and may be due to congestion pricing.
This study was designed to isolate the effect of congestion pricing on air quality. Vehicle traffic contributes roughly 14% of PM2.5 and 20% of NOx emissions in New York City. If congestion pricing changed traffic volumes in the CRZ, adjacent neighborhoods, or neighborhoods near major routes around the CRZ, it could therefore change the level of air pollution in those communities.
Determining the extent that air quality changes due to any policy is challenging, since many things impact air quality from year to year, such as average temperatures, rainfall, the presence of wildfires (both here and in other parts of the U.S. and Canada), the electrification of buildings and vehicles, the price of gasoline, and changes in regulations here and in other states. A simple before-and-after comparison would not tell us how much of the change is due to congestion pricing. So instead, we studied the difference between the air quality levels we measured after congestion pricing and estimates of what the air quality would have been if there were no congestion pricing. We did this at each of the EJ neighborhood sites, for the CRZ as a whole and the rest of NYC.
We did this by comparing the air quality results at locations where traffic volumes may have changed due to congestion pricing to a location where there was no expected change in traffic volumes. This study selected a site on the Van Wyck Expressway as its control for two reasons: it is a high-traffic highway without parallel, alternative routes, so any changes in traffic should reflect general background trends, and modeling results from the environmental review process predicted that there would be no change in traffic due to congestion pricing. We used before-and-after data from the control site to help predict what the air quality would have been elsewhere if congestion pricing had not been implemented.
This gives us projected “business as usual” air pollution values. We then use statistics to compare the projected to measured observed air quality data after congestion pricing was implemented. If the difference between the projected and observed values is statistically different than zero, then air pollution levels were affected by congestion pricing.
This is called an interrupted time series study with control. In addition, the model takes into account temperature, wind and precipitation, and both long term and seasonal trends in air pollution. To date, the Health Department’s analysis is the most comprehensive evaluation of congestion pricing’s impact on air quality.
To understand the results from our air pollution analysis, we also looked at the change in total traffic and truck traffic counts on the highways in the EJ communities. Like air quality, traffic is impacted by many factors beyond just congestion pricing. Weather, road closures, construction, regular maintenance, crashes and disabled vehicles, emergency response, and other events can all impact vehicle volumes. The periodic traffic counts collected were seasonally adjusted and compared before and after congestion pricing to see if changes aligned with the patterns we saw in the air pollution levels. More detail on traffic data collection and analysis can be found in the Detailed Traffic Analysis Methodology Appendix.
Did congestion pricing affect air quality near the ...?
Data source: Integrated monitors
Air quality changes throughout the day
We used real-time monitors to get a detailed picture of PM2.5 levels throughout the day, capturing rush-hour and overnight patterns with hourly measurements. These data let us examine correlations with traffic volumes. Notice that the time of day when the traffic is highest (such as morning and evening rush hour) is not always the time of day that PM2.5 is highest. This is because other sources of PM2.5, like building heating and restaurant cooking, contribute to the levels of PM2.5 in the air. The same is true for the other pollutants that we measured, and this helps explain why we saw no significant change in air pollution levels at some sites, even though traffic went down.
This chart shows us data from the Major Deegan Expressway monitor.
Data source: Real-time monitors
Pollution outside of NYC
At EPA monitoring sites shown on the map below, average PM2.5, ozone and NO2 levels from July to September 2025 were similar to values measured at the same sites from 2022 to 2024 during July through September.
The slightly higher levels at sites farther away from the CRZ in Connecticut and Eastern Long Island suggest that regional pollution levels remained similar or even increased slightly in 2025. These results show us that if we did not use a control site in our evaluation, we might have concluded that any increase in pollution at our monitoring sites was due to congestion pricing when it could have been the result of wider, regional patterns like wildfire smoke, state and federal changes in regulations, or even changes in the price of gasoline.
Conclusion
This analysis evaluated whether congestion pricing affected air pollution levels in neighborhoods that have been monitored for years through the New York City Community Air Survey. Additional monitoring supported by MTABT allowed us to determine whether levels of PM2.5, NO2, NO, and BC were different than they would have been if tolling had never been implemented.
We found that at EJ neighborhood sites that we monitored — where there were concerns about increased traffic and its effect on air quality — the measured pollution levels were not significantly different because of congestion pricing. The changes in pollution levels from 2024 to 2025 (before and after congestion pricing) continue the gradual decline in air pollution that we’ve been tracking throughout the city over the past 18 years.
Similarly, within the CRZ, neighborhood pollution levels were not significantly different because of congestion pricing.
That congestion pricing would only have a small impact on air quality is consistent with the Final Environmental Assessment and not unexpected: Traffic makes up only about 14% of PM2.5 emissions and 20% of NOx emissions. This means, for example, that a roughly 10% reduction in traffic volume in the CRZ would not substantially change air pollution compared to other sources of emissions.
The documented benefits of congestion pricing — reduced congestion, transit system improvements and investments through the committed mitigation — clearly demonstrate the overall benefit of the program.
Resources
- MTABT CRZ Tolling Page
- MTA Open Datasets
- Detailed Traffic Analysis Methodology Appendix (PDF)
- New York State DOT Traffic Dataviewer
- US EPA Air Quality System
- CBDTP Air Quality Evaluation Methods (PDF)
- Public Transit is Public Health
All air quality data used in this analysis are available by contacting NYCCAS.