I don't smoke in cars anyway, but if you have the windows open while moving the air is being replaced constantly. I'm not sure why anyone would question that? It's not a virus where you only have to catch one tiny portion to be infected. Hands up anyone who has ever said (in a car or a house) "I'll just open the windows to get some fresh air"
That research seems very confused or maybe badly reported.
"Traveling with a smoker in a car even with windows rolled down can be compared with an evening spent in a smoky bar according to the researchers"
That's a pretty unscientific statement.
Most journeys would be shorter than an evening in a bar.
In a bar there might be someone smoking all the time whereas the driver of a car might only smoke once.
They make no mention of speed so either this is based on a stationary vehicle or it didn't occur to the researchers that it would make a difference.
"The study has carefully measured the particulates or separate particles released into the air when a person smokes a cigarette while seated in a car"
Well guess what. The amount will be identical to that of a person sitting in a bar or standing in a field in a hurricane. It's the amount reaching/surrounding others that would be the concern.
They also seem to be comparing other pullution with the smoking particulates (not all of which are harmful btw), but since it's not clear what they were trying to say I can't argue with that.