? Probably the best example is a 1995 Iowa Department of Transportation study on the
use of ground shingles as a surface treatment on an unpaved road. [8] Approximately
300 tons of tear-off shingles were ground to pieces less than 1-inch, and approximately
600 tons of tear-off shingles were ground to less than 2-inch pieces. The two sizes of
shingles were mixed together prior to use. 500 tons of the processed shingles were
applied onto newly lain crushed limestone. The shingles were graded back and forth to
achieve a uniform shingle/limestone mixture of about 2.5-inch in thickness. After two
years of observations, the study concluded that shingles are very effective for dust
control on rural roads, result in better lateral control of vehicles, reduced the loss of
granular material into the ditches, and resulted in a quieter and smoother roadway.