Impacts of a low-emission zone on air pollutant and greenhouse gas emissions in Warsaw
To address concerns related to transport-related air quality, policymakers in Warsaw, Poland, have proposed the implementation of a low-emission zone (LEZ), restricting access to vehicles that don’t meet certain emission standards. Using real-world emissions data obtained from a 2020 TRUE remote sensing campaign in Warsaw, this study examines the impacts of two LEZ implementation options and analyzes their effects on air pollutant and greenhouse gas (GHG) emissions. Option 1 gradually strengthens restrictions every 2 years from 2024 to 2034; Option 2 tightens restrictions each year at a more accelerated pace from 2024 to 2028. Key findings from the analysis include:
- An LEZ targeting older diesel vehicles certified to Euro 4 or below (registered before 2011) in the early phase of implementation could reduce air pollutant emissions in Warsaw significantly. Implementation Option 1 could achieve a 50% reduction in fleet-average NOx emissions by 2027 and fleet-average PM emissions by 2025, compared to 2023 levels. LEZ Option 2 could reduce both NOx and PM emissions by 50% one year earlier.
- By 2035, both LEZ implementation options could reduce fleet-average NOx emissions by 95%, which is around 13 years earlier than without an LEZ. Likewise, all LEZ scenarios could reduce fleet-average PM emissions by 88% by 2035, or around 7 years earlier than without an LEZ.
- LEZ Option 1 could reduce fleet-average well-to-wheel GHG emissions by 50% compared to 2023 levels, around 6–9 years earlier than with no LEZ. LEZ Option 2 could accelerate the 50% reduction of well-to-wheel GHG emissions compared to 2023 levels by 1–4 years earlier than LEZ Option 1. Furthermore, the effectiveness of an LEZ to reduce GHG emissions depends on the actions of affected drivers. If drivers impacted by the LEZ Option 1 choose to replace their non-compliant cars with 100% used vehicles, fleet-average well-to-wheel GHG emissions could be reduced by 50% by 2036. If drivers shift to alternative zero-emission mobility options like cycling, walking, and public transport, the same 50% reduction could be achieved by 2033.
- The greatest cumulative savings for well-to-wheel GHG emissions could be achieved when affected vehicle owners switch to zero-emission mobility options. Under this scenario, LEZ Option 1 could avoid 31% of the cumulative well-to-wheel GHG emissions that would be emitted until 2038 in the absence of an LEZ. Likewise, LEZ Option 2 could avoid 45% of the same emissions.