I have not read the study, but I would hope that they had the cyclists wearing the same clothes and riding on the same stretch of road in all tests. Otherwise y

I have not read the study, but I would hope that they had the cyclists wearing the same clothes and riding on the same stretch of road in all tests. Otherwise you will end up with the situation where helmeted riders are more likely to be riding fast on roads that aren't as safe for cycling, Which would naturally lead to differences in driver behavior around them.