The amount of damage to tires is proportional to the fourth power of the weight per axel. That means that for the same journey, a bike sheds (3000 kg / 80 kg)ˆ4 so about 20 million times less. Assuming that the rubber is the same—and not that it has proprietary chemistry that may or may not contain carcinogens. Eight orders of magnitude of difference feels relevant.

Almost every train I know use metal wheels. We can look at the few that don’t, but something tells me people who raise that argument don’t want to look at alternative wheel composition, but rather hope to seed doubt and, in private, lobby replace one metro with thousands of cars, and I’m not sure that’s a good idea.

So, please, don’t come in here with that bullshit.

Lovely tone, you sound like a really nice person.

I never mentioned train wheels at all. Their brake pads are made from things like carbon, ceramic, and resin compounds. These wear down like any brake pads and so cause the same dust pollution. Remember that some trains in the world are over a mile long and have over 1000 wheels.

I dont see anybody claiming that bikes or trains cause anywhere near the same level as cars, but it is important to remember that they still do cause some and so they are not a silver bullet. Solutions still need advancing in order to completely remove these pollutants from human transportation systems.