The study was led by Cornell University researcher H. Oliver Gao and appeared in the journal npj Clean Air. It looked at the first six months of New York’s “Congestion Relief Zone,” where drivers now pay to enter Manhattan south of 60th Street. The researchers found a clear drop in harmful air pollution—specifically, tiny particles that can cause serious lung and heart problems.
Pollution levels inside the toll zone dropped by about one-fifth, and smaller improvements showed up across the city and surrounding suburbs. The biggest changes happened over time. In the first week, the drop in pollution was modest. But by five months in, air quality had improved much more noticeably.
The study did not look at health outcomes or travel behavior directly. It doesn’t tell us whether fewer people drove, more took transit, or how traffic patterns changed. It focuses only on the pollution data—though the authors suggest the cleaner air may reflect changes in how and when people travel.
Still, the message for other cities is clear. Road pricing can improve local air quality in a short period, without waiting on big infrastructure projects. As driving practices and technologies change, pricing tools like these could become a key part of urban transportation policy.
Other research in recent years supports this idea. Reviews of similar programs around the world show that pricing works best when paired with other transit options. Studies also suggest that toll systems can be designed to protect lower-income drivers while still reducing traffic.
For city leaders, the lesson isn’t just that tolling is possible. It’s that smart pricing, backed by good data and gradual rollout, can help cities cut pollution, manage traffic, and pay for better transportation options. New York’s results may not be a perfect fit for every city—but they offer a real-world example that others can learn from.
Cities should stick to the basics of governing