AlllOH S513E0

NBSIR 79-1707

Impact Attenuation Performance

of Surfaces Installed Under

Playground Equipment

Bal M. Mahajan

William B. Beine

1

Product Safety Technology Division

Center for Consumer Product Technology

National Bureau of Standards

February 1979

Report To:ler Product Safety Commission

QC \/estbard Avenue

2QQ Ja, Maryland 20016

.U56

79-1707

NaKonal Bnroati of StaiKfariM MAY 1 4

NBSIR 79-1707

I

* ' IMPACT ATTENUATION PERFORMANCE

OF SURFACES INSTALLED UNDER

PLAYGROUND EQUIPMENT

Bal M. Mahajan

William B. Beine

Product Safety Technology Division

Center for Consumer Product Technology

National Bureau of Standards

February 1979

Report To: Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, Maryland 20016

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

ABSTRACT

This report describes a test method and a suggested criterion for

evaluating the impact attenuation performance of playground surfacing

materials intended to protect against head injury due to falls. Several

types of surfacing materials have been tested and the results are included.

These results indicate that some surfacing materials impart peak

accelerations below this criterion for fall distances up to 10 feet while

others exceed the criterion for relatiavely short fall distances.
TABLE OF CONTENTS

INTRODUCTION

Purpose and Scope

Background

HEAD INJURY AND TOLERANCES

Head Injury

Tolerances

METHODOLOGY FOR TESTING SURFACES . . .

Test Method for Impact Attenuation

Impact Performance Criteria . . .

TEST MATERIALS AND METHODS

Material

Specimen Size

Headform and Drop Apparatus • . . Instrumentation

Test Procedure

TEST RESULTS AND DISCUSSION

Presentation of Test Results- - - Discussion

Page

1

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7

77

78

8

10

10

11

CONCLUSIONS 13

REFERENCES
INTRODUCTION

Purpose and Scope

In 1975, the Consumer Product Safety Commission (CPSC) responded to a petition to develop a standard for Public Playground Equipment and selected

the National Recreation and Park Association (NRPA) to develop such a standard. The NRPA thereupon formed a development panel, consisting of

representatives from consumer, industry, and buyer/installer communities

and called upon the Franklin Institute Research Laboratories for technical

assistance. Approximately one year later, in April 1976, the NRPA

submitted a proposed standard to the CPSC J_/. The CPSC elected to revise

that standard and sought technical assistance from the National Bureau of

Standards (MBS). In November of 1977, a project was initiated at MBS for

this purpose. A major task of this revision was to expand section 1514.10,

"Surfaces Under Equipment," of the standard proposed by NRPA for probable

publication as a separate Federal guideline for surfaces under equipment.

It was recognized that such a guideline should provide information on the impact attenuation performance of various surfaces and on such related

factors as cost, durability, maintenance, resistance to weathering,

sanitation, etc. The scope of the NBS effort was limited, however, to the

impact attenuation performance of surfaces. The objectives of this effort

were: 1) to develop a methodology for assessing the impact attenuation

performance of surfaces in relation to head injury, and 2) to test surfaces

commonly installed under playground equipment to determine which surfacing

materials, if any, are capable of providing protection against head injury

that might result when a child falls from equipxnent and impacts the

surface. Due to the large variety of surfaces that can be installed under

equipment, it would be impractical to test all such surfaces. Therefore,

it was decided to test approximately ten commonly used surfacing materials,

with some materials comprising two or three surfaces depending upon the

depth of materials. The results of this task would provide CPSC with

information useful in the formulation of a final version of the surfacing

guideline.

Background

The majority (60 to 10%) of public playground related injuries occur when users fall from equipment and impact the underlying surface V, 2/ &

V. The surfaces beneath playground equipment that have been identified as "injury agents" in falls include asphalt, bare ground, concrete, gravel,

sand and synthetic turf 2/. Nearly half of the injuries resulting from

equipment-to-surface falls are head injuries, ranging in severity from

minor scalp bruises to skull fractures, concussions, and death. Head

injuries resulting from such falls were the cause of death reported in two

in-depth investigations; in both cases the underlying surface was asphalt

3/.
- 2 -

Concern about child safety has prompted some sponsors and builders of

playgrounds to install energy absorbing surfaces (such as rubber mats,

synthetic turf, sand, wood mulch, etc.) beneath the equipment. However,

information on the ability of surfacing materials to provide protection

against head injury resulting from equipment-to-surface falls has not been

readily available.

Roth and Burke _4/ and NRPA V did test various surfacing materials for

their ability to provide protection against head injury. These

investigators used different criteria and procedures; hence, their results

are not comparable. For example, Roth and Burke used two different head'

simulators in their testing program and measured peak acceleration, while

NRPA y used still another type of head simulator and measured average

acceleration. Relatively little has been done to develop a standard

methodology (that is, criteria and test procedures) to assess the impact

attenuation performance of surfaces in relation to head injury.
- 3

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HEAD INJURY AND TOLERANCES

Before discussing the development of a methodology to test surfaces

for their ability to attenuate impact and reduce the risk of head injury

due to falls, it is appropriate to consider first the types of head

injuries that are likely to occur and the tolerance of the human head to

impact.

Head Injuries

Head injuries can be grouped into three major categories according to

site: scalp, skull and brain. Skull fractures and brain injuries are much

more serious than injuries to the scalp; and consequently, they are the

most important to be protected against. Although skull fracture can occur without brain injury ^/, Gurdjian 6/ reports that concussion (the most

ccxnmon brain injury) is associated with 80 percent of linear skull

fractures. Impact-induced head injury is a complex subject, and a discussion of all aspects of such injuries is beyond the scope of this

report. However, information on the various types of head injuries and

their relative severity, head injury mechanisms, and the effects of

important physical factors on resulting injury may be found in references 7

through 11. The following general description of immediate post- impact

effects leading to skull and brain injuries are considered to be adequate

for the purposes of this report.

When the head impacts a surface or when an object impacts the head,

the head is subjected to an impulsive force. The magnitude, direction and

duration of this impulsive force depends primarily upon the impact

momentum, as well as on the mechanical properties of both the head and the

object. Depending upon the contact area and the part of the head contacted

during impact, the force generated may cause deformation of the skull,

linear acceleration of the head, rotation of the head with respect to the

neck and torso, or combinations of these.

Deformation of the skull may be expected when the contact area is

sufficiently small, and this may contribute to skull fracture and

concussion. These deformations are usually accompanied by head

acceleration. Head acceleration without significant deformation is likely

to result when the impulsive force is distributed over a large area. For

example, this may occur when the head strikes a resilient surface or a surface consisting of loose material, such as sand.

Linear acceleration may cause relative motion of the brain with

respect to the skull and changes in intracranial pressure. Either of these

effects can lead to concussion. The severity of the resulting concussion

will depend on the magnitude and duration of head acceleration.

Rotation of the head with respect to the neck and torso produces

stretching of the neck ligaments, cervical cord, and brain stem. It may

also produce relative motion between the skull and brain and changes in
4

intracranial pressure. These consequences of head rotation can produce

injury to the neck, cervical cord and brain.

Tolerances

The Wayne State University Tolerance Curve (WSU curve) , shown in

figure 1 , was developed to predict human tolerance to linear fracture -and concussion 12/ and 13/. Based on experiments conducted on cadavers and

animals, it is probably the best known device for predicting the tolerance

of human head to impact. The WSU curve indicates that concussion is a function of both time and acceleration. When plotted on log“log paper, the

WSU curve is a straight line for impulse durations between 2.5 and 50

milliseconds. Gadd 14/, using the slope of this straight line as the

exponent of acceleration, devised the Severity Index (SI) as a measure of

head tolerance to impact. Mathematically, SI is expressed as follows:

v^ere a is the acceleration expressed in units of g, the value of

acceleration due to gravity. A value of SI equal to 1000 was suggested by

Gadd as the threshold for concussion.

In a recent study, Mohan, et. al. 15/ reported that a conservative

estimate of head injury tolerance limits for head-first falls of children are 150-200 g’s average acceleration for 3 milliseconds, or 200-250 g's

peak acceleration. These estimates were made by simulating falls of

children using the Motor Vehicle Manufacturers' Association (MVMA) TwoDimensional Crash Victim Simulator computer model and comparing the results

with actual incidents. This study represents the only known work that

specifically deals with head injury tolerance for children.
- 5 -

METHODOLOGY FOR TESTING SURFACES

Test Method for Impact Attenuation

There is a history of test method development for investigating the

impact attenuation capability of various products, especially protective

headgear. All of the recent test methods require dropping an instrumented

headform in guided free fall and measuring some linear acceleration

response of the headform during impact. Due to time and resource

constraints, it was necessary, as well as desirable, for this project to

take advantage of the technology already developed in this field.

Test headforms (such as the American National Standard Institute

(ANSI) rigid headform, the Wayne State University resilient or humanoid

headform, and the University of Michigan, Highway Safety Research Institute

resilient head-neck system) have been and are being used for testing the

adequacy of head protection provided by headgear. Of these, the ANSI rigid

headform is most frequently specified in current headgear standards because

it is easily reproduced and has been shown to provide reasonably repeatable

results. In addition, the ANSI headform has been shown, under some conditions, to correlate with the Wayne State humanoid headform. In

addition to such correlation, the acceleration responses of the two

headforms was very similar. Differences in the headform response were on the order of 20%, with the metal headform giving the higher accelerations

16/.

In the interest of simplicity and reproducibility of test apparatus,

it is proposed to test the impact attenuation capability of surfaces by

utilizing the ANSI rigid headform and associated test equipment.

Furthermore, the ANSI headform gives a more conservative estimate of head

response than does the resilient headform. It is further proposed to use the monorail drop apparatus, which is simplier to set up than the guidewire drop apparatus specified in the ANSI standards. Moreover, most future

headgear standards are expected to specify its use.

Impact Performance Criterion

Because surfaces beneath the playground equipment are esst-ntially

flat, the likelihood of depressed skull fracture is much less than the

likelihood of linear skull fracture and/or concussion. Most of the

concussion data for humans (e.g., the WSU curve) were deduced from linear

skull fracture data 1 3/. It follows, therefore, that the establishment of

a performance criterion should be guided by linear skull fracture data.

Also, it is advantageous to establish such a criterion in terms of peak

acceleration because this greatly simplifies the testing procedure.

Therefore, the most useful data for this purpose should be those where the

response is measured in terms of peak acceleration when the impact load,

due to head-first drop, is increased to the fracture level. Such

measurements were made by Hodgson, et. al. 13/, by dropping adult cadavers
head-first onto a flat surface. Peak accelerations in the range of 190 to

370 g’s were observed at the fracture level.

The impact performance criterion for surfaces should also be guided by

head injury tolerance data for head-first falls of children. As indicated

earlier, Mohan et. al. 15/ developed such data and estimated peak

acceleration in the range of 200-250 g’s as the tolerance limit. These

data are in good agreement with those reported by Hodgson, et. al. These

data suggest that the risk of serious head injury due to head-first fall is

minimal when the peak acceleration imparted to the head is 200 g’s or less. Therefore, as the impact attenuation performance criterion, it is

proposed that a surface should not impart a peak acceleration in excess of

200 g’s to the instrumented ANSI headform.
- 7

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TEST MATERIALS AND METHODS

Materials

A survey was conducted to determine the types of surfacing materials

that are, or may be, utilized as surfaces beneath public playground

equipment. For this survey several playgrounds were visited, and various

personnel associated with the construction and planning of playgrounds

(such as school construction administrators, architects, and personnel of

park commissions) were consulted. It was found that the most commonly used

material is in-place soil; other materials which are often used include

asphalt, concrete, crushed stone, pea gravel, rubber mats, sand, shredded

tires, saw dust, tan bark, wood chips, etc.

Based on the findings of this survey and consultation with the CPSC’s

technical officer, the eleven materials listed in table 1 were selected for

the test progran. It was decided to use two thicknesses (given in table 2)

of each material to form the test surfaces. It was also decided to conduct

the tests for both dry and wet surface condition for loose materials, but

only for dry conditions for unitary materials (rubber mats, gym mats, and

synthetic turf).

Asphalt and concrete were not included in the testing program because

the data obtained by NRPA V and by Roth and Burke V indicated that, even

at low velocity impacts, these materials would not meet the recommended 200

g criterion. Soil was not included because it was felt that the test

results would not be meaningful due to the wide variations in composition

and conditions that may occur from one geographic location to another.

Specimen Size

Since the cross-sectional area of the test surface may affect the test

results, particularly for surfaces composed of loose material, a series of

preliminary tests were conducted to determine the appropriate specimen

size. These tests vjere conducted with sand in square containers having

sides of 8, 12, 18 and 24 inches* in length. The results are presented in

figure 2 for four different drop heights. These tests indicate that the

change in headform response is negligible for containers with sides

exceeding 18 inches. Based on these results, an 18 X 18 inch container was selected for testing loose materials. For unitary materials, such as mats

and synthetic turf, it was subjectively judged that the specimen should be

at least 6 by 9 inches.

Headform and Drop Apparatus

The monorail drop apparatus (figure 3) and the size "C" ANSI headform

equipped v;ith accelerometer were used for testing the impact attenuation

performance of the test surfaces. The headform was attached to its support

assembly, which guides the headform on the monorail during free fall. The

base of the monorail was surrounded by a 26 by 24 by 12 inch container,

*Quantitative data contained in this report are presented in the U.S.

Customary Units of measure. The following equivalents can be used to

derive the metric units: inches X 2.54 = centimeters; feet X 0.3048 - meters.
- 8 -

which housed the surfacing material under test. The surface beneath the

test material consisted of a solid steel block, which was 14 inches in

diameter and 6 inches thick.

The height of the drop apparatus used in the test program limited the

maximum distance through which the test headform could be dropped to 10

feet or less. It is recognized that some playground equipment extends to

greater heights, hence consideration was given to investigating a procedure

that would permit testing at greater drop heights, A suggested procedure

is to spring load the headform guidance assembly at the top of the

apparatus prior to release. This provides a greater velocity than that

acquired in free fall, thereby increasing the effective drop height.

Results of testing indicate that this procedure is feasible. However, time

and resource limitations precluded the testing of surfacing materials at

extended drop heights.

Instrumentation

A velocity meter was used to measure the velocity immediately before

impact.

A piezoelectric linear accelerometer, placed at the center of mass of

the headform, was used to measure the acceleration imparted to the

headform. The output of the accelerometer was channeled through a signal

conditioner and charge amplifier and then into a storage oscilloscope and

also into a Severity Index (SI) analyzer. The instrumentation, with the

exception of the SI analyzer, was selected and operated in accordance with

3AE Practice J211b requirements for channel class 1000.

Test Procedures

Loose Materials . Loose materials to be tested were placed in the 13

by 18 inch frame containing the steel block base (i.e., the base surface)

to form as even a surface as possible. The depth of the material directly

above the steel block was maintained at either 4 or 6 inches.

The instrumented headform was dropped (first drop) on this surface

from various heights and data (impact velocity, peak acceleration imparted

to the headform, SI, velocity change experienced by the headform, and pulse

duration) were recorded. The headform was dropped a second time (second

drop) into the depression left by the first drop from the same height, and

data were recorded. After the second drop, the surface was leveled and

brought back to the initial thickness; the above procedure (the first and

second drop) was repeated at least twice without changing the drop height.

The tests were repeated at increased drop heights until the headform

response exceeded either an SI value of 1000 or a peak acceleration value

of 250 g's.

This procedure was followed for all of the loose materials tested.

Tests were conducted with 4 and 6 inch material thicknesses and with both

dry and wet surface conditions. For wet conditions, the surfacing material
- 9

-

was soaked for at least 15 hours in a separate container and transferred to

the test container for the wet test; before testing, the excess water was drained from the material by means of a sump pump. After the tests were completed at one drop height, the test surface was resaturated by

sprinkling one gallon of water on the surface and draining off the excess.

Unitary Materials . A specimen of the test material, as provided by

the manufacturer, was placed on the steel block base (base surface). The

headform was dropped on the test surface from various heights and data

recorded. The test was repeated at least twice at each drop height. In

some cases, double thicknesses of the material were tested. As with the

loose materials, the procedure was repeated at increased drop heights until

the headform response exceeded either an SI value of 1000 or a peak

acceleration value of 250 g's.
- 10 -

TEST RESULTS AND DISCUSSION

Presentation of Test Results

Impact attenuation performance data were obtained in terms of pc^ak

acceleration response of the headform as a function of impact velocity.

Because friction in the guidance system of the headform drop apparatus can vary from one apparatus to another, as well as from test to test, impact

velocity is a more significant measurement parameter than drop height. The

equivalent free fall height, H, may be calculated from impact velocity, V, as

H = V^/2g

where g is the acceleration due to gravity.

Other variables were monitored during the tests (SI, velocity change,

and pulse duration) but are not necessary for evaluating the impact

attenuation performances of surfaces; they are not presented here.

Figures 4 through 25 show peak acceleration as a function of impact

velocity for different materials. The result of each drop and a least

squares fit of each series (except those in figures 13 and 21) are provided

on each plot. The nature of the materials yielding the data in figures 13

and 21 required alternative methods for summarizing the data. Figure 13

depicts a curve obtained from an exact fit (a quadratic over a linear

expression) of four (x., y.) pairs where the y. are the average peak

accelerations for each^of the four clusters of^x. (velocity). The trace of

figure 21 through the points obtained from tests^using wet material (0- on this plot) comprises two line segments. The relatively horizontal segment

resulted from a least squares fit of the data. The near-vertical segment was formed by passing a line through the end point of the least squares

trace and the average velocity and peak acceleration of the three outlying

observations.

The curves of figures 4 through 25 are presented to summarize the

observed dependence of peak acceleration on velocity (or, equivalently,

free fall distance). One of two regression models

y = a + bx + e

or

2 y=a+bx+cx +e

was used for analysis.

Intuitively, a first or second degree (i.e., linear or quadratic)

model probably best illustrates the underlying relationship between

stimulus and the observed physical response. Higher order models will
n

always provide a better fit to observational data, but this contradicts the

profnise of simple monotonic relationships. In consequence, if a poor fit

is indicated between model and data, this may be attributed either to

instrumentation error or to the test material itself. In these

experiments, the accuracy of the equipnent was repeatedly checked by means

of an established calibration procedure, hence any systematic error is

probably due to the lack of homogeneity in the composition of the material.

Information to determine the adequacy of fit of a model to the data is

contained in the residuals, that is, the deviations of the actual observed

values about the values predicted by the model. (A thorough discussion on testing the adequacy of fitted models can be found in Draper and Smith,

1966 17/). In brief, the sum of squared residuals can be decomposed into

two parts: a component due to "pure error" and the other due to "lack of

fit." Dividing each component by its associatedpdegrees of freedom results

in the mean sums of squares for "pure error" (S ) and "lack of fit" (MS. ),

respectively. The usual procedure to test the Adequacy of the model is to

form the ratio,

MSl

F~ratio — —

and obtain the corresponding percent point of the F-distribution having the

appropriate degrees of freedom. If this percent point is less than some specified rejection criterion, say the 95th percent point (corresponding to

a level of significance, a = 0.05) there is no reason to reject the model.

Table 3 provides the necessary information to determine how well each model

fits the data; namely, the F-ratio and its corresponding percent point.

Discussion

It can be observed from figures 4 through 25 that, in general, wet

surfaces performed better than dry surfaces. One exception was material G

(cocoa shell mulch, see figure 21). When wet, this material bottomed out

abruptly, resulting in peak accelerations which exceeded the proposed

criterion.

The data of figure 21 are of particular interest. They show that the

performance of material G (wet) changed abruptly from a set pattern at a certain impact velocity, suggesting that other materials (both wet and dry)

might also exhibit similar behavior at impact velocities beyond the range

of the test impact velocities. It is recommended that the test data

presented for a given material should not be used to predict performance at

higher impact velocities than shown.

As might be expected, these data also indicate that, in general, the

thicker surfaces (thickness b) performed better than thinner surfaces

(thickness a). One exception was material C (pea gravel). For this

material performance was not noticeably affected by a change in the surface
12 -

thickness. Material C also provided poor impact attenuation (see figures 6

and 17), so would not meet the proposed criterion.

For purposes of canparison, the performance of surfaces with

thicknesses "a" and "b" of all materials tested are reproduced in figur-es

26 and 27 respectively. An examination of these figures reveals that most

loose materials performed better than the unitary materials, and F (pine

bark nugget), performed the best of all the materials tested.

Figure 28 shows the data for the first and the second drops (see test

procedure) for both thicknesses of material A, while figure 29 shows the

second drop data for thickness "a" of all materials. These data indicate

that, for loose materials, the peak acceleration response of the test

head form is considerably higher for the second drop than for the first

drop. This phenomenon apparently occurs because the loose material is

pushed away and somewhat packed by the first drop, so that the second drop

is essentially on a surface of lesser thickness. In actual use, this

phenomenon may also occur as a result of routine activities such as jumping

or running on the surface material. Consequently, a surface consisting of

loose material would require regular maintenance to insure constant

effectiveness. One alternative might be to install the material in

sufficient thickness to reduce the effects of casual jumping and running;

this may reduce the frequency of maintenance.
13 -

CONCLUSIONS

The impact attenuation performance of surfaces, in relation to head

injury due to falls from playground equipment, can be tested by dropping

the instrumented ANSI headform on the surface and measuring the

acceleration response of the headform. As the impact attenuation

performance criterion, it is proposed that a surface should not impart a peak acceleration in excess of 200 g's to the instrumented ANSI headform.

Surfaces composed of six inches of loose materials such as pine bark, sand,

shredded tires and shredded wood bark imparted peak accelerations which

were below this limit for drop heights up to 10 feet. Surfaces composed of

one layer of unitary material exceeded the criterion at drop heights of 5

feet or less.

The scope of this project did not permit an in-depth examination of

the performance of surfaces at higher impact velocities or of the effects

that a range of material thicknesses, compaction, and moisture content

would have on impact attenuation performance. Further testing would be

required to fully evaluate these factors.
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TABLE 1 . Surfacing Materials Tested

Designation

Loose

Materials

Unitary

Materials

Material Description

All purpose sand

Whole tire crumb, 1/2 inch shreds

Pea gravel, 3/8 inch mesh

Pine bark, mini-nuggets

Shredded hardwood bark

Pine bark nuggets

Cocoa shell mulch

Crushed stone (blue stone dust)

Outdoor rubber mat, 1 1/2 inches thick

Indoor gym mat, 1 1/2 inches thick

Synthetic turf on 3 inches thick asphalt base

(turf was bonded to resilient pad)
TABLE 2. Summary of Tests Performed

Surfacing Surface Thickness

(inches)

Surface Conditions

Material (a) (b) Wet Dry

A 4 6 X X

B 4 6 X X

C 4 6 X X

D 4 6 X X

E 4 6 X X

F 4 6 X X

G 4 6 X X

H 4 6 X X

I Single 1 Double X

J Single Double^ X

k2 3/8 5/8 x3 X

1 One pad on top of the other fonned the test surface.

2

3/8 and 5/8 inch thickness indicates the thickness of the resilient pad

between the turf and the asphalt base.

3Only the surface with thickness "b" was tested wet.
TABLE

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TIME-MILLISECONDS

Figure 1. Wayne State Concussion

Tolerance Curve.
002


 n

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 <S) 
 ir> LO

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PER

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Figure 3. Metal Headform on Monorail
UELOCITY

(FPS)
400

Figure

5.

Impact

Attenuation

Performance:

Material

B,

Depth - 4

inches
v/et

Figure

6,

Impact

Attenuation

Performance:

Material

C,

Depth - 4

inches
400

CLUJ<rihii <i o oLU -3 ixi D:: <r I- »-• o 2:

Figure

7.

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Attenuation

Performance:

Material
400

UELOCITY

(FPS)
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9.

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Attenuation

Performance:

Material

F,

Depth - 4

inches
400

Impact

Performance

Attenuation:

Material

G,

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inches
400

Impact

Performance

Attenuation:

Material

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Depth - 4

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Figure

12.

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Material

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Single

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400

Impact

Attenuation

Performance:

Material

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Depth

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Performance;

Material
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Impact

Attenuation

Performance:

Material

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Material

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Depth

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400

Impact

Attenuation

Performance

Material

D,

Depth - 6

inches
400

Impact

Attenuation

Performance:

Material

E,

Depth - 6

inches
400

Figure

20.

Impact

Attenuation

Performance:

Material

F,

Depth
400

UELOCITV

(FPS)

Impact

Attenuation

Performance:

Material

G,

Depth

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inches
400

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Material

H,

Depth

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Impact

Attenuation

Performance:

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Double

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orv

Impact

Attenuation

Performance:

Material

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Attenuation

Performance:

Material

K,

Thickness

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inch
Free

Fall

Distance

(Feet)

Relative

Impact

Attenuation

Performance

of

Different

Materials

Conditions:

DryDepth A
Free

Fall

Distance

(Feet)

Figure

27,

Relative

Impact

Attenuation

Performance

of

Different

Materials

Condition:

DryDepth D
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 •S' s

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Distance

(Feet)

UELOCITV

(FPS)

Figure

29.

Relative

Impact

Attenuation

Performance

of

Different

Materials

Conditions:

Dry,

Depth

A,

Second

Drop
ACKNOWLEDGEMENT

The authors wish to thank Mr. Raymond G. Russell for his valuable

contribution to the experimental phase of this study. The authors also

wish to thank Mr. James E. Harris for his contribution to the experimental

program, and Ms. Laura Nesbitt for her help in summarizing the data.
REFERENCES

1. NRPA, "Proposed Safety Standards for Public Playground Equipmpent and

Supporting Rationale," submitted by NRPA to CPSC, May 1976.

2. McConel, W.H. et al., "Product Investigation Report Contract No.

FDA73-6, Public Playground Equipment, October 15, 1973.

3. CPSC, "Hazard Analysis of Injuries Relating to Playground Equipment"

(NIIC-1201-75-M005), March 1975.

4. Roth, H.P. and Burke, D.M. , "Head Impact G in Free Fall on Various

Surfaces and Padding Materials," unpublished work submitted by D.M.

Burk to CPSC, April 1975.

5. Thomas, L.M. , Hodgson, V.R., and Gurdjian, E.S., "Skull Fracture and

Management of Open Head Injury," Neurological Surgery, Vol. 2, W.B.

Saunders Co., Phila., 1973.

6. Gurdjian, E.S., and Schuwan, H.K., "Management of Skull Fracture

Involving the Frontal Sinus," Annals of Surgery, Vol. 95, 1932.

7. Douglass, J.M., Nahrn, A.M., and Roberts, S.B., "Applications of

Experimental Head Injury Research," Proc. 12th Stapp Car Crash

Conference, S.A.E., 1968.

8. Gurdjian, E.S., "Recent Advances in the Study of the Mechanisms of

Impact Injury of Head," reprint from Clinical Neurosurgery, Vol. 19,

1972.

9. Mahajan, B.M. , "Standards for Athletic Helmets - A State-of-the-Art

and Reconmendations , " NBS Report No. NBSIR73-276, April 1974.

10. Rowbothan, G.F., "Acute Injuries of the Head," Williams and Williams,

Baltimore, 1964.

11. Gurdjian, E.S., "Prevention and Mitigation of Head Injuries," Reprint

from Neurosurgery, Vol. 19, 1972.

12. Synder, R.G., "State-of-the-Art: Human Impact Tolerances," S.A.E.

Paper No. 700398, 1970, reprinted in 1972.

13. Hodgson, V.R., Thomas, L.M., and Prasad, P. , "Testing the Validity of

the Severity Index," Proc. of 14th Stapp Car Crash Conference,

S.A.E. , 1970.

14. Gadd, C.W., "Use of a Weighted-Impulse," Proceeding of 10th Stapp Car

Crash Conf . , Society of Automotive Engineers, New York, 1966, pp. 164

174.
15. Mohan, D. , Bowman, B. , Snyder, R.G., and Foust, D.R., "A Biomechanical

Analysis of Head Impact Injuries to Children," presented at the Ninth

Annual Neuroelectric Society Meeting, December 1977.

16. Berger, R.E. and Calvano, N. , "Methodology for Choosing Test

Parameters to Evaluate Protective Headgear," NBS Report No. NBSIR78-

1547, November 1978.

17. Draper, N. , and Smith, H. , Applied Regression Analysis, John Wiley and

Sons, New York, NY.
NBS-114A (REV. 9-78)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR79-1707

Z, Reciptfent's AcCftfsion No.

4. TITLE AND SUBTITLE

IMPACT ATTENUATION PERFORMANCE OF SURFACES INSTALLED

UNDER PLAYGROUND EQUIPMENT

5. PuDlication Date Fabruarv 1979

7. AUTHOR(S)

Bal M. Mahajan and William B. Beine

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

11. Contract/Grant No

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS fsrreet, city, st^te, ziP)

Consumer Product Safety Commission

5401 Westbard Avenue

Bethesda, MD 20016

13. Type of Report & Period Covered

15. SUPPLEMENTARY NOTES

I

I Document describes a computer program; SF-185, FIPS Softvrare Summary, is attached.

16. ABSTRACT (A 200-word or less factual summary of most significant informatiofi. If document includes a significant bibliography or literature survey, mention it here,)

This report describes a test method and a suggested criterion for evaluating

the impact attenuation performance of playground surfacing materials intended

to protect against head injury due to falls. Several types of surfacing

materials have been tested and the results are included. These results

indicate that some surfacing materials impart peak accelerations below this

criterion for fall distances up to 10 feet while others exceed the criterion

for relatively short fall distances.

17. KEY WORDS (s ix to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Playground surfaces; performance; impact; peak acceleration; head

injury criterion; test method

18. AVAILABILITY r^Unlimited

j

For Official Distribution. Do Not Release to NTIS

J Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

; Order From National Technical Information Service (NTIS), Springfield, VA. 22161

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF

PRINTED PAGf.

22. Price

USCOMM-DC
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