Did a Transformative Public Transport Investment Improve Air Quality? Elizabeth Line in London

Oregon Convention Center 

Public transport is commonly connected to advantages such as mitigating traffic congestion and improving air quality. The Elizabeth Line, introduced in 2022, represents the most significant single increase in London's transport capacity in over 70 years. Connecting surrounding cities, a major airport, and central employment centres, this line is anticipated to increase the rail capacity in central London by 10%. Using meteorological normalisation for confounding control, repeated change point detection for response identification via hypothesis testing, and a regression discontinuity design for causal inference, our study finds heterogeneous responses in air pollution across different places in London. Changes in NO2 concentrations ranged from -9% to 0% in the short run and -15% to 0% in the long run. The comparison across different regions reveals more significant pollution reductions in inner and outer London at the town-wide level, whereas central London experienced greater decreases near roads. Our findings highlight the potential of public transport improvements in mitigating air pollution while emphasising the importance of accounting for the spatial heterogeneity of effects.

Air Pollution

Causal Analysis

Public Transport

Meteorological Normalisation

Change Point Detection 

Section on Statistics and the Environment