This study was originally conducted by the National Center on Accessibility at Bradford Woods between 1997 and 1999.
The purpose of this project is to compare the effectiveness
of surface treatments for creating a trail accessible to people
with mobility impairments. Specifically, this study is examining
the longitudinal effects of surface treatments on surface firmness
and stability, the costs of applying the treatments, and their
relative maintenance demands.
What is being tested:
The trail base contains compacted soil indigenous to central Indiana.
The types of surfaces used were Quarter Minus Limestone, #11 limestone
(refers to stone size), and indigenous soil. Quarter Minus Limestone
is a by-product of crushed limestone in which the limestone fines
are no larger than a quarter inch and most fines are dust particles.
A Longitudinal Trail Research Program on Soil Stabilizers
All surface materials were applied in 3-inch depths. The stabilization
products used with the surfaces were Mountain Grout*, Road Oyl
Resin Modified Emulsion, and Stabilizer. Mountain Grout* is a
single component hybrid polyurethane system designed to stabilize
and solidify soils. (*Mountain Grout has since been changed and
renamed). Stabilizer is a concentrated organic (ground seed hulls)
soil additive powder. Road Oyl Resin Modified Emulsion is a pine
resin emulsion and is not petroleum based.
- To evaluate the surface, a device called a Rotational Penetrometer
that measures the firmness and stability was used. This tool
evaluates the surface by measuring how deep an eight inch pneumonic
wheel that has a constant pressure of forty pounds will penetrate
the surface when rotated 90 degrees.
- Each one of the test plots is evaluated on a monthly basis,
with readings being taken in random locations on each evaluation.
Five different measurements are taken of each surface every
- The same location is never measured twice in one month.
- The test surface has received a large amount of foot traffic
over the last two years. The plots are on the main path at Bradford
Woods that connects the dining facility to the rest of the camp.
This trail has an average of seventy-five users per day.
- The test surfaces of the trail were lined with 2" x 6" boards
to designate the sides of the trail and separate each surface
Note: The Rotational Penetrometer is used as a standard measurement
device in the ANSI/RESNA Standard for Ground and Floor Surfaces
After Two Years of Use:
1. Quarter Minus Limestone with Stabilizer
This test plot has shown considerable wear and is breaking down
at the sides. The results of this test so far have indicated that
this surface has had an average of .36 -.59 inch penetrations.
2. Quarter Minus Limestone with Road Oyl Resin Modified Emulsion
This plot has shown little wear and is holding up well under all
the trail use. There is an average penetration of .05 -.08 inches
on this surface. This surface has proven to be very usable by
people with mobility impairments.
3. Quarter Minus Limestone with Mountain Grout Soil Stabilizer
This plot has shown the least wear of all test plots, the average
penetration on this plot was .009 -.03 inches.
4. Quarter Minus Limestone
This test plot has had an average penetration of .10 - .90 inches.
This plot has shown instability when wet and under adverse temperature
changes. This surface has degraded and broken down much faster
than other surfaces where stabilizers have been applied.
5. 50% #11 Limestone and 50% soil
This surface has an average penetration of .45 - 1.2 inches, it
has been the second worst surface in terms of decay.
This surface has had the poorest results over the last two years;
the average penetration is .35 -1.80 inches. When wet, people
with mobility impairments have deemed this surface inaccessible
and the surface has shown a substantial amount of decay.
7. Soil and Mountain Grout
This surface has an average penetration of .21 - .87 inches with
signs of decay on the edges of this test plot and in the middle.
Minus Limestone with Mountain Grout Soil Stabilizer
Minus Limestone with Road Oyl Resin Modified Emulsion
and Mountain Grout Soil Stabilizer
Minus Limestone with Stabilizer
#11 Limestone and 50% soil
ANSI/RESNA Standards for Firmness and Stability
||>0.3 & <0.5
||>0.5 & <1.0
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