Another antihelmet legislation argument bites the dust

When Ian Walker's paper appeared in Accident Analysis & Prevention in 2007 purporting to show that cars drove closer to helmeted than unhelmeted cyclists, it was quickly used as another argument against helmet legislation. But as a long-time cyclist, something did not ring true. Jake Olivier, a statistician from Australia, had the same vibes and reanalysed Walker's data. His email describes the event and the results, and my interpretation is that another antilegislation argument is now dead. Olivier writes:

‘My re-analysis of Ian Walker's now famous naturalistic cycling study on motor vehicle passing distance has been published by PLOS ONE. My conclusion is that while vehicle size, cyclist distance to the kerb and city of occurrence (Bristol or Salisbury, UK) are important factors associated with close passing (<1 m), helmet wearing is not a significant factor. The real differences in passing distance when wearing or not wearing a helmet occur for distances greater than 1.5m. I first submitted this paper to AAP as it was the journal that published Walker's original work. It was primarily rejected on the grounds that there is no justification for the one metre rule (3 foot rule). My analysis was an assessment of helmet wearing relative to road safety policy that exists or is promoted in many jurisdictions. Still, that is why this paper is in PLOS ONE and not AAP. This work was actually two studies—one in road safety and the other statistical. They are meant to complement each other. The stats one is pretty dense, but it was needed to demonstrate (that) Walker overpowered his study, thereby misinterpreting his statistical results.’

(http://www.plosone.org/article/citationList.action;jsessionid=B57108C74B43A32BEF8E9F2A6AB85C9F?articleURI=info%3Adoi%2F10.1371%2Fjournal.pone.0075424)

Editor’s note: A fascinating paper, Editorial Decisions May Perpetuate Belief in Invalid Research Findings, also in PLoS ONE, (8:e73364. doi:10.1371/journal.pone.0073364) highlights the importance of publishing replications in the …