Suggests that fine and coarse PM for the light-rail line may indeed have a common source. It is reasonable to hypothesize that the primary source of particulate pollution for the light-rail line is from local emissions (vehicular traffic, road dust, photochemical reactions, etc.). The daily operations of the light-rail trains (i.e., movement of the train) may also affect PM levels, but their impact is expected to be considerably smaller, given its exposed environment.