Back in 2006, Dr Ian Walker of the University of Bath conducted an experiment you may be aware of within the context of the eternal helmet debate.
Cycling with and without a helmet and with and without a wig, he discovered that cyclists are afforded more space by passing drivers if they are (or at least appear to be) female or if they’re not wearing a helmet.
(In a separate study, conducted in 2013, Walker found that some drivers will pass too closely no matter that you wear.)
Bicycling.com reports that the helmet and wig study (not its official name) was questioned by researchers from the University of New South Wales in 2013.
They analysed the same data – 2,355 observations over 200 miles of riding – and concluded that “bicycle helmet wearing is not associated with close motor vehicle passing.”
They argued that that the average passing distances were greater than one metre – a distance that in some places would not be considered a “close pass.”
Walker and Dorothy Robinson have now responded to the response via a recently published paper in Accident Analysis & Prevention.
Referring to the University of New South Wales analysis, they write: “Their conclusion was based on omitting information about variability in driver behaviour and instead dividing overtakes into two binary categories of ‘close’ and ‘not close’; we demonstrate that they did not justify or address the implications of this choice, did not have sufficient statistical power for their approach, and moreover show that slightly adjusting their definition of ‘close’ would reverse their conclusions.”
They also present a new analysis of the original dataset, measuring directly the extent to which drivers changed their behaviour in response to helmet wearing. “This analysis confirms that drivers did, overall, get closer when the rider wore a helmet.”