A technique for analysing exhaust emission plumes from unmodified locomotives under real world conditions is described and applied to the task of characterizing plumes from railway trains servicing an Australian shipping port. The method utilizes the simultaneous measurement, downwind of the railway line, of the following pollutants; particle number, PM_2.5 mass fraction, SO₂, NO_x and CO₂, with the last of these being used as an indicator of fuel combustion. Emission factors are then derived, in terms of number of particles and mass of pollutant emitted per unit mass of fuel consumed. Particle number size distributions are also presented.

The practical advantages of the method are discussed including the capacity to routinely collect emission factor data for passing trains and to thereby build up a comprehensive real world database for a wide range of pollutants.

Samples from 56 train movements were collected, analyzed and presented. The quantitative results for emission factors are: EF(N) = (1.7 ± 1) × 10¹⁶ kg⁻¹, EF(PM_2.5) = (1.1 ± 0.5) g kg⁻¹, EF(NO_x) = (28 ± 14) g kg⁻¹, and EF(SO₂) = (1.4 ± 0.4) g kg⁻¹. The findings are compared with comparable previously published work. Statistically significant (p < α, α = 0.05) correlations within the group of locomotives sampled were found between the emission factors for particle number and both SO₂ and NO_x.