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At WesTrack, Its a Wrap
After simulating more than 10 years of
Interstate-level traffic loads in 2.5 years, the driverless trucks at
the WesTrack pavement testing facility near Reno, Nevada, have finished
their runs. Guided by wires buried in the hot-mix asphalt (HMA) pavement,
the four heavily ladentrucks traveled an average of 15 hours a day around
the 2.9-km (1.8-mi) oval test track. Their travels were designed to evaluate
how variations in HMA construction quality, such as asphalt content, aggregate
gradation, and compaction, affect pavement performance and to validate
the Superpave mix design and analysis procedures. By evaluating these
variations, researchers could advance the development of performance-related
specifications for HMA construction. Ultimately, these specifications
will help improve pavement performance.
Sensors in the tracks 26 test sections continually monitored the
pavements temperature and loads. Each pavement section was also
evaluated at regular intervals for signs of visual distress, rutting,
deflection, roughness, and friction.
Since the trucks completed their traffic loading activities in February
of this year, laboratory testing of the pavement materials and analysis
of the data collected have continued. This testing and analysis is scheduled
to conclude in January 2000. Because additional funding for WesTrack was
not included in the Transportation Equity Act for the 21st Century, the
work is being completed under the National Cooperative Highway Research
Program.
The
driverless trucks at WesTrack have simulated more than 10 years of
Interstate level traffic loads in 2.5 years. |
![roadway.](images/track.jpg) |
WesTrack was built and operated by a consortium of seven organizations:
the Nevada Automotive Test Center, Nichols Consulting Engineers, Granite
Construction Co., Harding Lawson Associates, University of Nevada at Reno,
Oregon State University, and University of California at Berkeley. Once
the project ends, the Nevada Automotive Test Center, the prime contractor
on the project, will assume ownership of the track.
The WesTrack project, says Terry Mitchell of the Federal Highway Administration
(FHWA), accomplished what it set out to do. It provided an important
early validation of the Superpave system. We learned a great deal. And
as planned, the WesTrack research is aiding in the development of performance-related
specifications for HMA pavements.
WesTrack has also proved valuable in analyzing why pavements fail. Several
test sections developed rutting in 1997 after carrying traffic for just
a few days. A team of independent experts determined that the pavement
failure was caused by high levels of voids in the mineral aggregate (VMA)
in the mix.
The teams report, which recommends capping the amount of VMA in
mix designs, is due out this month. For more information on the WesTrack
project, contact Terry Mitchell at FHWA, 202-493-3147 (fax: 202-493-3161;
email: terry.mitchell@fhwa.dot.gov).
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