4. Discussion
4.1. Main findings
We studied the spatial and temporal associations between modelled traffic-related noise and air pollution levels. Both noise and air pollution showed different spatial patterns, and correlations across postcodes varied substantially depending on the unit of analysis: London, London Boroughs, neighbourhoods and 1 km × 1 km grid cells. Correlations across all postcodes in London were moderate and varied depending on the exposure metrics between Spearman's rho of 0.34 and 0.55. Correlations were mostly stable across exposure tertiles, distance to major road and deprivation tertiles.