National Trail Surfaces Study

Rotational Penetrometer. The instrument used in field-testing to test for compliance with the Outdoor Developed Areas Guidelines firmness and stability recommendations. The Rotational Penetrometer, developed by Beneficial Designs, uses a wheelchair caster placed on a spring loaded caliber in a metal tripod frame which suspends the caster about 6 inches over the surface. When the caster is released, the spring load gauge replicates the force of an individual in a wheelchair over a given surface. The penetration into the surface is measured for readings of “firmness.” The test for stability requires the caster of the Rotational Penetrometer to be moved from side to side to determine the horizontal displacement of the surface material.