This article is more recent and better, using London as an example. Basically motorcycles are better. I can't imagine smokey pickups are somehow better
https://www.mag-uk.org/motorcycle-nox-emissions-are-old-motorcycles-really-highly-polluting/
"the standard set by TfL for NOx emissions for motorcycles is Euro 3 and specifically 0.15g/km. When we interrogate the spreadsheet we might expect that all pre Euro 3 motorcycles show an average in excess of 0.15 g/km at 30km/h to align with TfL’s position. However what actually find is that Pre Euro 1 <50cc mopeds, all 2 strokes, Euro 2 four strokes 250 – 750cc and all four strokes >750cc average below 0.15g/km. What is more, for the “dirty 2 strokes” that we all thought would be an issue, the modelled emissions are less than half the 0.15g/km standard!"