> 20% more wear of something that is 2x as polluting is 40% more pollution
If an equivalent car wore down its tires 20% slower, and those tire particles contributed 2x the intensity of pollution than other types of wear-based pollution, than the increase in produced pollution from that source seems like it would be ~16%, not 40%.
If one car drives 100 km and produces 2 units of pollution per km, that would be 200 units. Another car wearing 20% more would produce 240 units, or roughly ~16% more.
If an equivalent car wore down its tires 20% slower, and those tire particles contributed 2x the intensity of pollution than other types of wear-based pollution, than the increase in produced pollution from that source seems like it would be ~16%, not 40%.
If one car drives 100 km and produces 2 units of pollution per km, that would be 200 units. Another car wearing 20% more would produce 240 units, or roughly ~16% more.