Fig. 6From: Exhaust emission factors of greenhouse gases (GHGs) from European road vehiclesEffect of after-treatment system on the CH4 and N2O average emissions from diesel light-duty vehicles. Kruskal–Wallis statistical test with ns: p > 0.05, *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001Back to article page