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Music City Bus Lanes
Nashville, Tennessee
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Bus Lanes | Ultra-thin whitetopping (UTW) of an existing asphalt
pavement was used on downtown bus lanes for the Metropolitan Transit Authority
in Nashville, Tennessee. With 475,000 bus trips annually over the 4th and Deadrick
Streets bus transfer area, shoving and rutting of asphalt was a continuous problem.
Previously, the area was repaired approximately every twelve months. The Nashville
Public Works Department looked to UTW as a permanent solution. Ultra-thin
whitetopping is a process in which typically 2 to 4 inches (50 to 100 mm) of high-strength,
fiber-reinforced concrete is placed over a prepared surface of existing, but distressed,
asphalt. The resulting composite pavement delivers the long life and superior
performance characteristics of concrete pavement, at a cost competitive with asphalt
overlays. One of the most important considerations for this project (as
is typical with transit) was completion time-construction needed to occur within
a couple of days to reduce impact on bus service. The UTW pavement, in this case
averaging 4-1/2 inches (114 mm) in thickness, was constructed in several steps
during October 1994. The existing asphalt pavement was milled down, and the new
concrete was placed and screeded. Joints were sawn to create 4 foot x 4 foot (1.2
m x 1.2 m) segments shortly after placement. The finish was broomed for skid resistance
and then cured. With fast-track paving techniques, the surface was ready for traffic
in less than 48 hours. Tennessee has been a leader in the development and
use of UTW. Of special note are ultra-thin whitetopping projects on eight intersections
at six Knoxville city locations and two Knoxville County locations that were completed
between May and August 1997. A unique team-consisting of the Tennessee Department
of Transportation (Region 1), Knoxville County Department of Engineering &
Public Works, City of Knoxville Engineering Department, and concrete contractors
and suppliers-worked to solve an air quality problem stemming from failure of
traffic loop detectors at asphalt intersections. With the use of federal Congestion
Mitigation and Air Quality (CMAQ) funding, the reconstructed UTW intersections,
with working detectors, reduce vehicle delays, travel times, fuel usage, and vehicle
emissions.
Project Credits
Owner & Engineer: City of Nashville,
Nashville, TN
Contractor: Capitol City Contractors, Nashville, TN
Concrete
Supplier: Metro Ready Mix Concrete Co., Nashville, TN
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