[QUOTE 5000430, member: 9609"]Vehicles intake outside air just below the windscreen - on many SUVs this height could well be as high if not higher than a roadie on the drops.[/QUOTE]
So where is the air just below a car windscreen coming from?
Thanks to the bodywork shape, the stuff flowing over the air intakes is coming from a little way above road height (basically from a little above the bottom of your front spoiler/skirt), pretty much right where the car in front's exhaust is venting. Not long ago, a fair chunk of that dirtiest air would be used to cool the engine, but current cars don't take in anywhere near as much air for cooling as they used to.
Now, where does the air that a roadie on the drops is breathing come from? (
source)
Much higher up. The exhaust-height air near the ground is left near the ground and at worst flutters around their legs. I suspect more upright town/trade bike users will have their air intakes even further from the crap, but it's not easy to find aero plots of them for some reason
I think it's pretty easy to see how car occupants suck tail pipes more than cyclists. Even if car occupants switch to e-bikes and they're not getting much exercise, the reduced pollution intake will probably do public health more good than if they switched to electric cars - that's one reason why it's so awful that government is subsidising e-cars but not e-bikes.