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As the Interstate system continues
to age, many concrete pavements are still very serviceable, but
exhibit very poor ride quality and even unsafe driving conditions.
Asphalt-rubber surface courses are selected more and more often
as the best choice to offer the driver better traction or skid
resistance, better visibility in wet weather, reduced hydroplaning
and most of all, reduced traffic accidents that result in injury.
 Which surface
do you want your family driving on?
Reduce splash and spray, increase
visibility, and striping contrast and reduce accidents by using
Asphalt Rubber Surfaces!
Asphalt rubber provides a stronger
bond in mixes that provide greater water drainage from the driving
surface during wet weather. These mixes are often called "open
graded" (OGFC) or "permeable" (PFC) friction courses.
The photo on the left shows an open surface in the far left lane
where the water is not present compared to a dense mix used in
the rest of the lanes during a highway resurfacing project. Open
mixes remove the water and rubber mixes last longer.
The increased visibility, less
splash and spray and better ride can reduce the occurrence of
accidents. Consider a case study from Texas:
Reduced Accidents
In 2002, an aged concrete pavement
on IH 35 in San Antonio, Texas needed to be rehabilitated. Asphalt-Rubber
was selected because of its proven durability in thin applications
over concrete. The weather conditions and traffic accident data
were analyzed in a twelve month period period just before the
Asphalt Rubber Permeable Friction Course and in a twelve month
period after the overlay.
The text boxes
below summarize the results, less accidents:
Traffic Accident data provided by the San Antonio Police Department
(SAPD) Climate data obtained from National Oceanographic and
Atmospheric Administration
It's Good to Stop Short
Highway traffic engineers regularly
measure the ability of vehicles to stop without skidding on the
pavements that they manage within their system. One of the measuring
devices they use is called a "Mu Meter" which is a
small trailer that has a wheel attached that can be braked while
the rest of the wheels on the trailer are not. Sensors on the
braked wheel measure the friction provided by the road surface
underneath. The higher the friction value the better the road.
The US Air Force provides a simple rating scale for the Mu Meter
below:
Good Skid Resistance Measured on
similar projects even after ten years or more!
The Arizona Department of Transportation (ADOT) has
been using rubber in friction courses since the late 1980s. Many
of the old rubber surfaces are still performing today. The table
below provides a look at some of the oldest rubber projects and
shows the excellent skid resistance even after 10 to 14 years.
 ADOT has a compared the performance
of Asphalt rubber friction courses to the  performance
of friction courses without rubber and provided system wide averages.
As can be seen in the chart to the right, new friction courses,
regardless of the material will have good skid numbers at about
65 right after construction. The asphalt rubber friction courses
stay good for longer whereas the regular materials wear out dropping
below 60 after ten years. At right, a dense graded surface is
seen in the background during a light rain, the rubber is in
the foreground, photo courtesy of Tenn. DOT. It's true; Asphalt-Rubber
can provide a safer surface for the driving public. Ask if Asphalt
Rubber is used in your community. If not, ask why.
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