Creating Chemistry

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.

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  1. Creating Chemistry
  2. Playground Safety Is No Accident
  3. A Playground For All
  4. High-Frequency Playground Inspections
  5. Safe Play
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