Bicycle helmet wearing is not associated with close motor vehicle passing: A re-analysis of Walker, 2007

OBJECTIVES: To re-analyse bicycle overtaking data collected by Walker (2007) with a view to assess factors associated with close passing (<1 m), to adjust for other observed factors in a multivariable analysis, and to assess the extent to which the sample size in the original analysis may have contributed to spurious results. METHOD: A re-analysis of 2,355 motor vehicle passing events recorded by Walker that includes information on cyclist's distance to the kerb, vehicle size and colour, city of observation, time of day, whether the event occurred while in a bikelane and helmet wearing. Each variable was considered for a final, multivariable model using purposeful selection of variables. The analysis was repeated using multiple logistic regression with passing distance dichotomised by the one metre rule. Bootstrap p-values were computed using sample sizes computed from conventional values of power and effect size. RESULTS: 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. CONCLUSIONS: 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.

• Record URL:
  • https://doi.org/10.1371/journal.pone.0075424
• Supplemental Notes:
  • © 2013 Jake Olivier and Scott R Walter
• Authors:
  • Olivier, Jake
  • Walter, Scott R
• Publication Date: 2013

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: e75424
• Serial:
  • PLoS One
  • Volume: 8
  • Issue Number: 9
  • Publisher: Public Library of Science
  • EISSN: 1932-6203
  • Serial URL: https://journals.plos.org/plosone/
• Publication flags:

  Open Access (libre)

Subject/Index Terms

• TRT Terms: Bicycle crashes; Bicycle helmets; Data collection; Distance; Helmet use; Motor vehicles; Passing; Statistical analysis; Variables
• Uncontrolled Terms: Bicycle safety; Sample size
• Geographic Terms: Bristol (England); Salisbury (England)
• Subject Areas: Highways; Pedestrians and Bicyclists; Safety and Human Factors; I83: Accidents and the Human Factor;

Filing Info

• Accession Number: 01499915
• Record Type: Publication
• Files: TRIS
• Created Date: Nov 25 2013 9:58AM