Safety-in-Numbers: Turning Conventional Wisdom on its Head ProWalk / ProBike September 13, 2004

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Safety-in-Numbers Turning Conventional Wisdom
on its Head ProWalk / ProBike September 13,
2004

• Peter L. Jacobsen
• Consultant
• Professional Engineer

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Safety-in-Numbers Schedule

• Findings (40 minutes)
• Peter L. Jacobsen, Consultant
• Michael P. Ronkin, Oregon DOT
• Turning Conventional Wisdom on its Head (20
  minutes)

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Safety-in-Numbers

• Increase Public Health
• Reduce injuries
• Increase physical activity
• Conflict?

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15 Most Dangerous California Cities to Bicycle?
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Bicycling in 68 California Cities
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Walking in 68 California Cities
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Walking and Bicycling in 68 California Cities
Healthier
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Prior Safety-in-Numbers Research

• Intersections
• Bicyclists at 95 intersections in Malmo, Sweden
• Bicyclists at 45 bike path intersections in
  Gothenburg, Sweden
• Pedestrians at 300 intersections in Hamilton,
  Ontario

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Walking and Bicycling in 47 Danish Towns
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Distance Bicycled in 14 European Countries
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Walking and Bicycling Trips in Eight European
Counties
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Less than one-for-one increase(Exponent less
than zero)
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Key Points

• Safety-in-Numbers
• Safer where more people walk or bicycle
• Causation consistent, replicable, plausible,
  dose-response relationship
• Tripling walking or bicycling
• Halves individual risk
• Increases total injuries by only 50
• Comparisons difficult

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Understanding the Cause of Safety-in-Numbers

• What causes Safety-in-Numbers?
• Human behavior
• Roadway design
• Laws
• Social mores
• Examine changes over time
• Which comes first?
• Does safety encourage activity?
• Or vice versa?

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Bicycling in United Kingdom and The Netherlands
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Key Points

• Roadway design, laws, and mores change slowly
• Behavior changes
• Who changes?
• Unlikely that where more people walk and bicycle
  they defer more to motorists
• Hence, likely that motorist behavior changes

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What Next?

• For safety, change motorist behavior
• How to encourage motorists to expect people?
• More walking and bicycling?
• Designate bike lanes?
• Mark crosswalks?
• Extend curbs at intersections?
• Control motorist speed?

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Peter L. Jacobsen

• jacobsenp_at_medscape.com
• 916-456-8645

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Extra Slides Not Used
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Better Medicine
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Consistent with Evidence

• Cochrane
• Victim-oriented
• Safety education fails
• Conspicuity fails
• Motorist-oriented
• Traffic calming works

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Safety-in-Numbers at Intersections
95 Intersections Ekman (1996)
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Safety-in-Numbers at Intersections
Motorist vs. Bicyclist Collisions at 45 Bike Path
Intersections Leden (2000)
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Defining Health

• a state of complete physical, mental, and social
  well-being, not just the absence of disease or
  infirmity.
• -- World Health Organization
• Salus Populi Suprema Lex
• -- Roman Law, 451 BC

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Causation

• Plausibility
• Consistency
• Strength
• Specificity
• Temporality
• Dose-response relationship
• Coherence
• Experimental evidence
• Analogy

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Walkability and Health

• Reduce disease
• Communicable
• Chronic
• Reduce injuries
• Reduce fear (Increase social capital)
• Clean environment
• Access to medical and social services
• Develop independent children

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Conflict!

• More walking bicycling to address chronic
  diseases
• Fewer injuries to people walking bicycling

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(No Transcript)
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Bicycling in the United Kingdom from 1950-99
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Bicycling in The Netherlands from 1980-98
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Injuries per Capita
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Amount of Bicycling
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Risk of Injury While Bicycling
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Safety in Numbers
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References

• Jacobsen PL. Safety in numbers more walkers and
  bicyclists, safer walking and bicycling. Injury
  Prevention 200392059.
• Raford N. Space Syntax An Innovative Pedestrian
  Volume Modeling Tool for Pedestrian Safety.
  Transportation Research Record 2004.
• Cochrane Reviews
• Interventions for increasing pedestrian and
  cyclist visibility for the prevention of death
  and injuries.
• Safety education of pedestrians for injury
  prevention.
• Area-wide traffic calming for preventing traffic
  related injuries.