Bicycle Helmet Safety Institute
The Helmet Update
Study: Helmets do not change passing safety
In 2007 we disputed the findings announced by Dr. Ian Walker that his study had proven that riders with helmets were given less safe passing clearance by cars on roadways.
We did not think his data actually showed that, since average passing distances were more than one meter, helmet or no.
A new study has gone beyond our comments and concluded:
The previously observed significant association between passing distance and helmet wearing was not found when dichotomised by the one metre rule. Other factors were found to be significantly associated with close passing including cyclists' distance to the kerb, vehicle size and city of observation (Salisbury or Bristol, UK). P-values from bootstrap samples indicate the significance of helmet wearing resulted from an overly large sample size.
After re-analysis of Walker's data, helmet wearing is not associated with close motor vehicle passing. The results, however, highlight other more important factors that may inform effective bicycle safety strategies.
Here is the full study, by Jake Olivier and Scott R. Walter