Earlier quoted context omitted.
OK, I'll need to see a source on increased pollution. I really doubt that a motorcycle is putting out more pollution than an average American-size vehicle. For example, my sport bike gets 59MPG, and I've owned multiple bikes that got >100mpg. Even without a catalytic converter, how is that more pollution than a single commuter driving in a truck or SUV getting 20MPG and likely shedding more road and tire particulate…
For exhaust emissions, motorcycles are often dramatically worse than modern vehicles with catalytic converters. https://gearjunkie.com/motors/motorcycle-vs-vehicle-emission...
See this article to show how a modern motorcycle would be ~100x less polluting than the example vehicle given in the article referenced:
https://www.acem.eu/new-euro-5-environmental-standard-for-mo...