This presentation examines whether the "safety in numbers" effect exists for cycling in Melbourne. Previous research found that as cycling and walking increased in other areas, injuries/fatalities only increased at a lower rate, though some question if this effect truly exists. The researchers analyzed cycling data from 2008-2014 and injury data, finding a linear relationship between kilometers cycled and injuries in Melbourne with no evidence of a safety in numbers effect. Possible reasons why are that critical mass for the effect has not been reached, infrastructure is not keeping up with cycling growth, or cycling culture involves more risk. Further research on injury trends over time and data discrepancies is needed.

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Cycling Safety in Numbers: Does it exist in Melbourne?
James Ramsey & John Richardson
AITPM National Conference 16 August 2017

2. Cycling Safety in Numbers: Does it exist in Melbourne?
This presentation:
• What is the ‘safety in numbers’ effect?
• Previous research findings
• Our research methodology
• Our findings
• Further research directions
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3. What is the ‘safety in numbers’ effect?
The ‘safety in numbers’ effect has been reported in other parts of the world
(Jacobsen, 2003, Fyhri, 2016).
It is the notion that as cycling participation increases, serious injuries and fatalities do
not increase linearly with participation, but rather increase at a lower rate.
Hypothesis is:
• As more bikes take to the road, drivers become more aware of riders.
May also be:
• Safer infrastructure is increasingly provided as cycling increases
• More riders = fewer drivers = less chance of conflict between cars and bikes
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4. Previous research findings
Jacobsen (2003) study found safety in numbers effects occurring for walking and cycling in
Sweden, UK, California and the Netherlands.
Found that as walking and cycling increased, injuries/fatalities only increased with the 0.4
power.
4
y = mx0.4
y = mx
0
1
2
3
4
5
6
0 1 2 3 4 5 6
Injuries
Amount of cycling/walking

5. Previous research findings
Does the safety in numbers actually exist though?
Bhatia & Wier (2011) are critical of the existence of safety in numbers effects and believe
the mechanisms driving the empirical findings are more complex.
They caution against policy makers relying on safety improvements occurring by
themselves.
How safe is Melbourne to ride a bike anyway?
Garrard (2010), found that Melbourne has an injury rate of around 12 to 31.5 serious
injuries per 10 million km travelled.
Comparable figures elsewhere: Netherlands (1.4), Denmark (1.7), UK (6), USA (37.5)
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6. Our research methodology
• We looked at total annual kilometres travelled by bicycle in each of
the 31 Local Government Areas (LGAs) in Metropolitan Melbourne.
– VISTA data from FY2008, FY2010, and FY2013-14
• Compared this to total annual bicycle serious injuries and fatalities
in each LGA.
– VicRoads CrashStats police reported data
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7. Our research methodology
• Calculated total kilometres travelled by LGA:
– VISTA trip origins and destinations
– Python based code to extract 5400 individual trip bicycle directions for GIS obtained from Google
Maps Directions API
7
Google Maps 2017

8. Our findings
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Kilometres cycled per annum* Serious injuries/fatalities per annum*
* Pooled data all years

9. Our findings
• Relative risk is broadly the same for inner, middle, and outer Melbourne
• But over time it is getting safer in all regional classifications
9
12.6
11.5
9.6
14.6
9.3
10.3
14.9
12.1
9.9
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
2008 2010 2013
Injuries/fatalitiesper10millkm
Inner Middle Outer

10. Our findings
10
y = 13.606x
R² = 0.8688
y = 10.376x
R² = 0.9254
y = 9.1187x
R² = 0.8434
-
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5 6 7 8
Fatal/seriousinjurybicyclecrashesperyaerperLGA
Kilometres bicycled per LGA per annum (10^7)
2007-08
2009-10
2012-14
Linear (2007-08)
Linear (2009-10)
Linear (2012-14)

11. y = 11.017x
R² = 0.955
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5 6 7Fatal/seriousinjurybicyclecrashesperyearperLGAavg.
Kilometres bicycled per LGA per annum (10^7) avg. of VISTA datasets
Our findings
Is cycling relatively safer in areas of
Melbourne where more cycling
occurs? We found:
Relationship between kilometres
cycled and injuries/fatalities is
linear in Melbourne.
There is no safety in numbers effect
showing that it is safer to ride in an
area which has more cycling
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12. Our findings
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• Why is there no safety in numbers effect in Melbourne?
– Assuming that there is such a thing:
• Critical mass of cycling for safety in numbers not yet reached?
• Infrastructure not keeping pace with growth in cycling?
• Different type of riding in Melbourne (riskier fitness / racing bike culture)?
– Assuming there is no such thing as the safety in numbers effect:
• It’s all down to infrastructure and policy (like lower speed limits)
– But then, infrastructure just isn’t delivering safety in Melbourne? Why?

13. Further research directions
• Why are injuries declining over time? Is this trend
significant?
• Discrepancy between hospital data and police data
13

14. References
Bhatia, R., Wier, M., (2011), '“Safety in Numbers” re-examined: Can we make valid or practical inferences from available
evidence?', Accident Analysis and Prevention, 43(1), pp.235-240
Fyhri, A., Bjørnskau, T., Laureshyn, A., Sundfør, H.B., and Ingebrigtsen, R. (2016), Safety in Numbers - uncovering the
mechanisms of interplay in urban transport. Institute of Transport Economics.
Garrard, J., Greaves, S. and Ellison, A. (2010). "Cycling injuries in Australia: Road safety's blind spot?" Journal of the
Australasian College of Road Safety 21(3).
Jacobsen, P.L, (2003). Safety in Numbers: more walkers and bicyclists, safer walking and bicycling. Journal of Injury
Prevention, September, p.205-209
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