Table 4.

Comparison of our estimated emission factors with those from the dynamometer study of May et al (2014) (May et al. 2014).

Vehicle Type	Study	Average Emission Factor [95% c.i.]
		CO (g/kg)	NOx (g/kg)	BC (g/kg)*
Light duty	This study	22.4 [19.7–25.0]	3.2 [2.8–3.6]	0.016 [0.011–0.021]
	May et.al. (51 LEV vehicles)**	26.4 [19.1.–33.7]	2.8 [1.8–3.9]	0.017 [0.013–0.022]
Heavy duty	This study	14.8 [9.9–21.9]	18.9 [8.0–35.3]	0.40 [0.29–0.58]
	May et.al. (2 vehicles with a DPF)***	0.26	8.2	0.001
	May et al. (3 vehicles without a DPF)**	8.8 [5.6–12.0]	23.6 [17.2–30.1]	0.18 [0.13–0.24]

^*May et al report EC values;

^**confidence intervals estimated from computed standard errors;

^***confidence intervals were not estimated due to the small number of samples