PRB Articles


Creating Chemistry

Albert Einstein is credited with saying, “Play is the highest form of research.”

If that is the case, then our nation’s playgrounds are our most important laboratories.

Playgrounds offer children challenge, excitement, and a place for strenuous physical activity that health experts tell us is vitally important.

Playgrounds are a place to test physical limits, interact socially in coordinated play, and learn first-hand the implications of the laws of physics.

Like most laboratories, playgrounds are risky places, but that is part of the fun. Despite the potential for injury, children are readily attracted by the challenge and excitement of taking risks.

On average, there are 200,000 visits annually to hospital emergency rooms across the country by children injured on playgrounds. These numbers include both public and home playgrounds. Most of these injuries are associated with falls.

Our challenge, as designers, is to maximize the sense of adventure and risk, while minimizing the potential for actual injury.

Experience and testing have shown that the two most important ways of accomplishing this goal are to:

1. Maintain proper fall zones in the immediate vicinity of equipment.

2. Provide resilient surfacing that can break a fall without causing injury.

Standard Of Care

There are no laws governing playground equipment and surfacing safety, but two documents have come to represent the “standard of care” for playground safety in the United States.

The first is a federal guideline prepared for the Consumer Product Safety Commission (CPSC), titled Handbook for Public Playground Safety; the second is the Standard Consumer Safety Performance Specification for Playground Equipment for Public Use, published by the American Society for Testing and Materials International (ASTM) Playground Safety Standard F1487.

Another testing protocol, ASTM F1292, Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment, has become the national standard for testing impact attenuation of playground surfacing materials.

A trade organization representing playground and surfacing manufacturers--the International Play Equipment Manufacturer’s Association (IPEMA)--provides third-party testing of equipment to ensure it meets the requirements of the documents identified above.

There is a truly broad range of play equipment that can be selected and combined to create unique play experiences for almost any situation. Designers and administrators limit exposure to risk of litigation by ensuring playground equipment is 100-percent IPEMA certified.

There is playground equipment that has been in use for some time, which experience has shown should be avoided due to safety concerns. Some examples include:

• Swinging exercise rings or trapeze bars

• Multiple-occupancy swings

• Spinning equipment without speed governors

• Swings attached to composite play structures

• Ropes or cables not affixed at both ends

• Heavy swings (made of metal or wood)

• Trampolines.

Maintain Fall Zones And Clear Zones

It is an art to create and combine play equipment in such a way that it is exciting and attractive to users, and it is not the intent of this article to downplay the importance of that process. However, due to the number and nature of injuries on playgrounds, the best value a designer or administrator can often bring to playground design is to ensure:

1. Equipment is properly spaced to allow for clear fall zones.

2. Safety surfacing will cushion falls so that emergency-room visits are not needed.

Fall zones for individual and composite pieces of equipment are fairly simple to figure out. For most platforms and pieces of equipment higher than 24 inches, there is a need to maintain a 6-foot-wide horizontal zone surrounding the equipment that is cushioned with safety surfacing and free of any posts, solid curbing, or other elements that might cause injury in a fall.

Fall zones can overlap in some cases, but in others they can’t. These are generally governed by the height of the equipment.

Additionally, it is important to note that some categories of equipment have added requirements for clear zones. These include swings, slides, spring toys, and merry-go-rounds. As an example, spring toys and merry-go-rounds are not more than 24 inches above the ground, yet they still require a 6-foot or greater clear zone around the perimeter.

It is important to verify clear-zone requirements; they can be found in the Standard Consumer Safety Performance Specification for Playground Equipment.

Most reputable play-equipment manufacturers provide clear-zone diagrams for each of the pieces of equipment they make, and these templates can be very helpful in developing a playground layout.

For those new to playground design, it is a good idea in the early stages of design to allow more space for a playground than you think should be required. It is not unusual for an elementary-school playground with multiple pieces of equipment to occupy 8,000 to 12,000 square feet of area.

Selecting Safety Surfacing

Playground safety surfacing is often addressed in playground design as an afterthought. In actuality, there is almost nothing more important. Selection of a surfacing type is a key decision, and should be made early in the design process.

Surfacing can be an aesthetic consideration as poured-in-place rubber, tiles, and rubber fill are available in a variety of colors, and can be coordinated with playground equipment.

Key considerations, however, for selection of surfacing materials include the following in order of descending importance:

• Impact attenuation and safety

• Americans with Disability Act (ADA) accessibility

• Initial cost and long-term maintenance (life-cycle cost)

It is telling that risk managers for school districts are often as well-versed as designers on the guidelines for safety surfacing and the characteristics of surfacing types. This is the case because lawsuits due to playground injuries are not uncommon, and the outcome is often dependent on whether the safety surfacing meets or exceeds the minimum criteria of ASTM 1292.

There are two measures used to determine fall attenuation for playground surfacing:

1. Head Injury Criterion (HIC)--a mathematical formula used to quantify the likelihood of head injury

2. Simple deceleration -- measured in G-max

Resilient surfacing should attenuate a fall such that HIC measures less than 1,000, and G-max measures less than 200. As the height of equipment increases, the depth of resilient surfacing for the fall zones of that equipment must also increase.

It is also important to understand that different materials have different resiliency characteristics. As an example, 9 inches of pea gravel will adequately stop a 6-foot fall. It only takes 2-1/2 inches of poured-in-place rubber resilient surfacing to provide the same resilient landing.

Most surfacing materials are tested in carefully established and optimum laboratory settings. Measurements of impact attenuation after installation may vary significantly from laboratory conditions, and the unique circumstances of a playground should play a role in what material is used for surfacing.

As an example, engineered wood fiber demonstrates excellent resiliency in a controlled setting; however, it tends to absorb and hold moisture. When frozen, engineered wood fiber can form a very dense surface with almost no resiliency; therefore, there are surfacing materials that may be more appropriate for locations where play equipment is used throughout harsh winter conditions.

Through maintaining proper fall zones and providing the best possible surfacing, designers can increase the safety of playgrounds without limiting the excitement and adventure for children.

Terry Schoenthal, ASLA, is a Landscape Architect practicing in Alaska. Terry has spent more than 25 years studying , designing , (and using) playgrounds in Alaska, Washington State, and Europe. Most recently, Terry has completed a study of resilient surfacing options for the playgrounds of the Anchorage School District.

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Resources For Playground Design

The design of playgrounds today has become a complex effort, but a number of reference and training sources are available and can be very helpful. Some examples include:

The Certification Course for Playground Safety Inspectors, presented by the National Recreation and Park Association. Two-day courses are held throughout the United States, and offer thorough training in current safety recommendations for playgrounds. Upon passing a test, participants are certified as Playground Safety Inspectors. Schedules for classes and schedules may be found at its website, www.nrpa.org .

ASTM F 1487-07 (or most current) Standard Consumer Safety Performance Specification for Playground Equipment for Public Use: This is the accepted general standard for playground-equipment safety.

ASTM F 2223-04: Standard Guide for ASTM Standards on Playground Surfacing: This is the accepted standard for playground safety surfacing.

ASTM F1292, Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment: This is the standard for testing the impact attenuation of safety surfacing.

Handbook for Public Playground Safety. Produced by the Consumer Product Safety Commission, this handbook is one of the accepted primary guides for playground design.

A Guide to Playground Planning, produced by the Illinois Department of Natural Resources. This is a great all-round resource for all of the decisions that go into developing a new playground, and can be found at www.dnr.state.il.us/ocd/IDNRPlaygroundManual.pdf .

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