Playground Surface TestingBackground Research
Martyn R. Shorten, Ph.D.
Portland Oregon, USA
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Playground Surfacing – Background Research
Injury RatesInjury Statistics
205,850 Emergency Room admissions during 1999
Frequency1 per 1.3 minutes
Occurrence1 per 1333 children
Accident TypeInjury Statistics
Collisions17%
Falls70%
Injury TypeInjury Statistics
LimbFractures
33%
HeadInjuries
10%
Cuts,Bruises,SprainsStrains
46%
FatalitiesInjury Statistics
Source: US CPSC: Tinsworth and MacDonald, 2001
147 deaths between January 1990 and August 2000
Head Injury75%Entrapment
Falls21%
Risk FactorsInjury Statistics
Equipment height
Equipment design
Parental supervision
Maintenance
Mixed use
Surfacing as a Risk FactorInjury Statistics
Falls to the surface:• 20% of deaths• 70-80% of injuries
Shock Attenuating Surfaces:• Potential for lower injury risk
Playground Safety InitiativesPlayground Surfacing and Playground Injuries
CPSC Handbook(1975)
Safety Advocates
Legislation
Equipment Design
Surfacing Standards
Playground Surfacing MaterialsPlayground Surfacing
Loose-Fill Surfaces• Organic
– Bark Dust– Wood– Engineered Wood Fiber
• Inorganic– Sand– Gravel– Shredded foam / rubber
Playground Surfacing MaterialsPlayground Surfacing
Unitary Surfaces• Rubber / Urethane• Poured-in-Place• Tiles
Performance CriteriaPlayground Surfacing
Standards• ASTM F1292• EN 1177, etc.
Performance CriteriaPlayground Surfacing
Standards• ASTM F1292• EN 1177, etc.
Fall Height
Performance CriteriaPlayground Surfacing
Standards• ASTM F1292• EN 1177, etc.
Fall Height
Test Method• Instrumented headform• Triaxial Accelerometer
Performance CriteriaPlayground Surfacing
Standards• ASTM F1292• EN 1177, etc.
Fall Height
Test Method• Instrumented
headform• Triaxial Accelerometer
Critical Fall Height
Performance CriteriaPlayground Surfacing
Historical efforts tobase performancecriteria on (head)injury risk data
g-maxHead Injury Criterion
Brain Injury Mechanisms
Diffuse Axonal InjuryBrain Injury Mechanisms
Normal Axons
Traumatized Axons
Metabolic Cascade:
• Ca and K ion release
• Disruption of neural function
• Compensation
• Increase energy expenditure
• Metabolic distress
• Increased vulnerability
Mild Traumatic Brain InjuryBrain Injury Mechanisms
Normal Axons
Traumatized Axons
Long Term Consequences:
• Second Concussion Syndrome
• Cumulative Effects
Abbreviated Injury ScaleBrain Injury Mechanisms
AIS 1 2 3 4 5 6Degree Minor Moderate Serious Severe Critical Survival
Injury Uncertain
Headache, DizzinessLoss of Consciousness
Skull FractureNeurological Damage
HemorrhageBrainstem DamageTissue Disruption
Abbreviated Injury ScaleBrain Injury Mechanisms
AIS 1 2 3 4 5 6Degree Minor Moderate Serious Severe Critical Survival
Injury Uncertain
Headache, DizzinessLoss of Consciousness
Skull FractureNeurological Damage
HemorrhageBrainstem DamageTissue Disruption
Abbreviated Injury ScaleBrain Injury Mechanisms
AIS 1 2 3 4 5 6Degree Minor Moderate Serious Severe Critical Survival
Injury Uncertain
Headache, DizzinessLoss of Consciousness
Skull FractureNeurological Damage
HemorrhageBrainstem DamageTissue Disruption
Impact Tolerance of the Brain
• Cadaver studies• Animal studies• Human volunteers
– Automotive Industry– Aerospace Industry– Military
AccelerationImpact Tolerance of the Brain
0
20
40
60
80
100
0 5 10 15 20Time, ms
Acce
lera
tion,
g
gmax
Wayne State CurveImpact Tolerance of the Brain
Gadd Severity IndexImpact Tolerance of the Brain
0
20
40
60
80
100
0 5 10 15 20Time, ms
(Acc
eler
atio
n)2.
5 /100
0
Gadd Severity IndexImpact Tolerance of the Brain
0
20
40
60
80
100
0 5 10 15 20Time, ms
(Acc
eler
atio
n)2.
5 /100
0
Head Injury CriterionImpact Tolerance of the Brain
Prasad-Mertz CurvesImpact Tolerance of the Brain
AIS
1
Prasad-Mertz CurvesImpact Tolerance of the Brain
AIS
1
Prasad-Mertz CurvesImpact Tolerance of the Brain
AIS
1
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ryPrasad-Mertz CurvesImpact Tolerance of the Brain
No InjuryAIS
1
Prasad-Mertz CurvesImpact Tolerance of the Brain
No InjuryAIS
1
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ryPrasad-Mertz CurvesImpact Tolerance of the Brain
No InjuryAIS
1
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ryPrasad-Mertz CurvesImpact Tolerance of the Brain
No InjuryAIS
12
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ryPrasad-Mertz CurvesImpact Tolerance of the Brain
No InjuryAIS
12
3
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ryPrasad-Mertz CurvesImpact Tolerance of the Brain
AIS
12
34
No Injury
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ryPrasad-Mertz CurvesImpact Tolerance of the Brain
AIS
12
34
5
No Injury
Prasad-Mertz CurvesImpact Tolerance of the Brain
AIS
12
34
5 6
No Injury
Prasad-Mertz CurvesImpact Tolerance of the Brain
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ry
AIS
12
34
5 6
No Injury
Prasad-Mertz CurvesImpact Tolerance of the Brain
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ry
AIS
12
34
5 6
No Injury
Prasad-Mertz CurvesImpact Tolerance of the Brain
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ry
AIS
12
34
5 6
No Injury
Prasad-Mertz CurvesImpact Tolerance of the Brain
HIC = 1000
Prasad-Mertz CurvesImpact Tolerance of the Brain
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
HIC Score
Prob
abilit
y of
Inju
ry
AIS
12
34
5 6
No Injury
Are Impact Tests Good Surrogates?Surface Shock Attenuation Tests
• Mass
• Energetics
• Geometry
• Flexibility
0
500
1000
1500
3 6 9 12Fall Height, feet
HIC
0
100
200
300
g-max
Critical Fall HeightPlayground Surfacing
0
500
1000
1500
3 6 9 12Fall Height, feet
HIC
0
100
200
300
g-max
Critical Fall HeightPlayground Surfacing
0
500
1000
1500
3 6 9 12Fall Height, feet
HIC
0
100
200
300
g-max
Critical Fall HeightPlayground Surfacing
Critical Fall Height:7 feet
0
1
2
3
4
Gravel Sand WoodChips
WoodFibre
ShreddedRubber
Cri
tica
l Fa
ll H
eig
ht, m
ete
rsShock Attenuation PerformancePlayground Surfacing Materials
25 cm uncompressed depth 15 cmthickness
Loose-Fill Unitary
Benefits of Shock AttenuationPlayground Surfacing
Non-conforming surfaces• 2.3 times greater injury risk
NonConforming
Conforming
Relative Injury Risk
Chalmers et al, 1996
2.3
1
Benefits of Shock AttenuationPlayground Surfacing
Non-conforming surfaces• 2.3 times greater injury risk
Surfacing MaterialsConcrete
Rubber
BarkDust
Relative Injury Risk
12
5
Mott et al, 1997
Relative Injury Risk
Benefits of Shock AttenuationPlayground Surfacing
Non-conforming surfaces• 2.3 times greater injury risk
Surfacing Materials
Severe head injuries
Sand
1
6
Sosin et al, 1993; Laforest et al, 2000
1.7
Grass
Asphalt
Impact Test IssuesPlayground Testing
Positives:
•Good faith attempt to evaluate injury risk
•Documented effectiveness
•Bias of risk estimates
“True” HIC EstimationAre Impact Tests A Good Surrogate
0%
20%
40%
60%
80%
100%
0 500 1000 1500
HIC Score
Prob
abilit
y of
Inju
ryAdjusted HIC scores
12
3
4
5
In-filled Conventional
Impact Test IssuesPlayground Testing
Limitations:
•Data QuantityApplicabilityValidity
•Method BiofidelityReproducibility and repeatability
Head injury focus
•Concussion
“Concussus”
“to shake violently”
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