NO: Quadruplets of pooled continuous and diffuse sampler NO-measurements: index stations (Ind), reference stations (Ref) before (pre) and after (post) introduction of LEZ.

Ind.diff and Ref.diff denote differences between index measurements and between reference measurements (negative post-pre differences indicate lower values after introduction of LEZ). Concentrations measured in µg/m3.N: number of quadruplets, Min: minimum, p5: 5th percentile, p50: median, mean: arithmetic average, p95: 95th percentile, max: maximum.