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LTPP Program Launches Traffic Data Pooled-Fund Study
To increase and improve the collection of monitored traffic data
for five of the long-term pavement performance (LTPP) program Specific
Pavement Study (SPS) projects, the Federal Highway Administration (FHWA)
has initiated a new State pooled-fund study. The study is the result of
a 1998 review of the LTPP data, which concluded that the spatial distribution,
timeliness, quantity, and quality of the monitored traffic data needed
to be improved to ensure the success of the SPS -1, -2, -5, -6, and -8
experiments.
The SPS experiments were designed to learn how such factors as cumulative
traffic loading affect pavements of different compositions, environmental
conditions, and layer thicknesses. However, it is estimated that at least
half of the SPS -1, -2, -5, -6, and -8 sites do not have the quantity
and quality of traffic data that is needed for analysis.
Following the 1998 review, the Transportation Research Board (TRB) - LTPP
Committee and the American Association of State Highway and Transportation
Officials Task Force on SHRP Implementation recommended a pooled-fund
study as a way of filling in the gaps. The total cost of implementing
the study through FY 2003 is estimated at $10 million. While the study
is targeted to those States with SPS sites, participation by other States
is encouraged, given that all States will benefit from the increased understanding
of pavement performance that the SPS experiments will provide. To date,
18 of the 37 States with SPS experiments have expressed interest in joining
the pooled-fund study, while 12 have indicated that they prefer to meet
their data collection commitment individually.
FHWA plans to kick off the study by conducting site visits to all SPS
projects to evaluate the site, perform a baseline test of the pavement
smoothness, and check the calibration of the site's weigh-in-motion (WIM)
sensors. The quality of data obtained from WIM sensors, which collect
information on such factors as vehicle and axle weights, is highly dependent
upon the pavement in which they are installed. Smoother pavements provide
more accurate and less variable measurements. Once the site visits have
been completed, a report will be prepared, providing a baseline for future
data analysis and site evaluations.
A set of protocols has been developed for use nationally for verification
of scale performance; pavement smoothness requirements; model WIM system
specifications, including accuracy requirements and construction guidelines;
and data collection processing. These are available on the Web at http://www.fhwa.dot.gov/pavement/ltpp/spstraffic/.
FHWA's LTPP team plans to conduct a series of pilot projects to validate
the protocols and train highway personnel in annual WIM evaluation activities.
Highway agencies that are interested in participating in the pooled-fund
study or who want more information should contact Larry Wiser at FHWA,
202-493-3079 (fax: 202-493-3161; email:
larry.wiser@fhwa.dot.gov).
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