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Those preventive maintenance treatments include
crack sealing, fog seals, chip seals, thin cold-mix seals, surface
recycling, and hot-mix asphalt thin overlays, including dense-, open-, and
gap-graded mixes that will bolster ride quality, provide surface drainage
and friction, and correct surface irregularities.
Many road agencies that are wedded to existing
practice — ranging from old-fashioned cities in which an alderman or
councilman decides where the road funds are spent, to state DOTs where
highway building and rebuilding take utmost priority — are disinterested or
ambivalent regarding programmed pavement preservation, especially when it
means shifting funds from favored programs, and there is no central
authority to compel them to do otherwise.
Some states have implemented pavement preservation
programs. Under a new FHWA program in 2005, the National Center for Pavement
Preservation is reaching out to those state agencies that will cooperate to
gauge the depth of pavement preservation in their agencies.
Mega-municipalities such as Los Angeles, down to
small townships like Minisink, N.Y. have adopted pavement preservation
programs. And new types of governments that merge city with county have
embraced pavement preservation, such as the Metropolitan Government of
Nashville & Davidson County (Metro Nashville).
Management and maintenance
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| Within context of its pavement management system,
Los Angeles is base-recycling worst-condition roads using foamed asphalt or
asphalt emulsions. |
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| Los Angeles uses rubberized slurry seal to prolong
pavements as indicated by its Pavement Condition Index within its pavement
management system. |
One might say that pavement management + pavement
maintenance = pavement preservation. The pavement preservation community is
pulling out all stops to bridge that crucial gap where pavement management
systems and inventories meet with maintenance activities in the field.
Too often, maintenance is not driven by pavement
management, said Katie Zimmerman, P.E., Applied Pavement Technology, in a
presentation at the 2003 Transportation Research Board meeting in
Washington, D.C. In the presentation Integrating Preventive Maintenance Into
Pavement Management Systems, co-authored by David Peshkin, P.E., also of
APTech, Zimmerman said that, traditionally, the highest priority is given to
correct safety deficiencies. “Treatments are triggered when a pavement
section falls below an acceptable level,” she said. “Funding for routine
maintenance is typically unreliable, so treatment application cycles vary.”
Turf wars within an agency can choke pavement
preservation. “Maintenance and rehabilitation are often programmed by
different groups within the highway agency,” Zimmerman told TRB.
“Maintenance activities are frequently not reported in accordance with a
referencing system used by pavement management. The same maintenance
treatment can be used as a preventive, corrective, or stop-gap treatment.”
But more recently, road agencies are beginning to
integrate preventive maintenance into planning and design activities,
reducing the life-cycle cost of preserving a pavement through the use of
preventive maintenance. Through planned, early application of preventive
maintenance treatments, good roads are kept in good condition, validating
the motto of pavement preservation being “the right treatment for the right
road at the right time.”
Last year, an analysis by Midwest Regional
University Transportation Center, University of Wisconsin-Madison, concluded
that most state agencies are ambivalent to the pavement preservation message
because of sheer inertia.
“The preventive maintenance philosophy is somewhat
contrary to that of traditional public administration for primarily two
reasons,” MRUTC said, as reported in Better Roads (April 2005,
Making
High-Volume Roads Last Longer). “First, it requires strategic rather than
operational analysis on the part of agency managers and elected officials.
That is, the benefits of preventive maintenance, which are best expressed in
terms of future value, are intrinsically undervalued by management concerned
with current operating costs.”
Demonstrations of long-range savings can help alter
attitudes, but it’s difficult, the center said. “Although life-cycle cost
analysis and other techniques have made progress toward overcoming this
difference in cost-benefit perceptions, the operational mode of thought
stands in the way of broader preventive maintenance implementation.”
The benefits of integrating preventive maintenance
with a pavement management system were described in a 2005 TRB presentation,
Potential Benefits of Integrating Preventive Maintenance into New Jersey
Pavement Management System, by Helali, Bekheet, Jackson, Jumikis, and
Zaghloul.
The New Jersey Department of Transportation
established a pavement preservation strategy that emphasizes preventive
maintenance and moves away from the worst-first approach, they wrote. “To
be able to implement the PM program and show its benefits and the merits
over the existing worst-first approach, NJ DOT decided to integrate the PM
program into [its] PMS.”
The proposed PM program consists of two components,
one short-term and one long-term. “The short-term component involves an
annual crack sealing/filling program, and addresses the current needs of the
network,” the authors said. A long-term component involves staged
treatments, in which the rehabilitation and PM treatments are combined and
integrated in the form of a long-term preservation program, perhaps over two
decades. The final product would be a multi-year maintenance and
rehabilitation program for the entire network, which is based on economic
analysis and optimization.
New initiative for states
To jump-start recognition of pavement preservation,
the FHWA’s Office of Asset Management has recently launched a Pavement
Preservation Technical Assistance Program to help highway agencies define
their pavement preservation programs, and to build a pavement preservation
database.
The National Center for Pavement Preservation at
Michigan State University in East Lansing, Michigan, is coordinating with
individual states and the local FHWA division offices to conduct interviews
to discuss procedures, policies, and programs associated with pavement
preservation. “The goal is to help states assess where they are and provide
comments and recommendations on what they can do to further develop and
enhance their pavement preservation programs,” said Tom Deddens of the
FHWA’s Construction and System Preservation Team.
“Over the next two years, the FHWA Office of Asset
Management will lead an effort to conduct a series of comprehensive
technical reviews and evaluations of DOTs’ pavement preservation programs at
the request of individual states,” said FHWA’s Geiger. “For each appraisal,
we will conduct approximately 80 hours of program review and interviews of
key personnel and provide both an oral closeout and a written report
highlighting strengths, identifying gaps, and making recommendations for
improvement of that DOT’s program. The contract will consist of a maximum of
10 such reviews during the first year, with the likelihood that the effort
will be extended by 10 more such reviews in FY 2006.”
Pavement preservation is a powerful tool through
which any highway agency can improve pavement condition and significantly
prolong its life within existing budgets, Geiger told FHWA regional
directors, administrators, and engineers. “The focus must be to keep good
pavements in good condition, preserving the pavement asset while maximizing
the economic efficiency. Our experience with preservation programs is
showing that DOTs are gaining flexibility for funding capital needs while
providing the traveling public higher level of service. Pavement
preservation provides greater value to the highway system, improves safety,
enhances mobility, and provides a higher level of satisfaction of highway
users.”
NCPP charged with outreach
To execute the outreach this year, the FHWA has
turned to the National Center for Pavement Preservation. NCPP has been
fighting for change in the conventional wisdom, and observes that the
majority of the United States population travels through a work zone at
least once per day, and that 80% of federal-aid funds go into products the
public sees in work zones. NCPP wants to redirect the conventional thinking
that new construction is most desirable, and that worst pavements should be
fixed first. Instead, it wants to promote efficient road preservation
programs for highway agencies.
For this 2005 project, NCPP is charged with working
within the goals of each state, and is visiting as a facilitator and
advisor. For each visit, the NCPP will visit with agency personnel involved
in the development, implementation, and management of the state’s
preservation program.
"We have been contracted by the FHWA to conduct the
state appraisals," NCPP's O'Doherty told Better Roads. "We have 20 states
this first year with many more signing up for the second year. We will go
into each state, spending a week visiting people at headquarters, districts,
division and regional offices, and will be looking at some roads. We will
make an appraisal that when completed can be used as a plan by the agency.”
“This would include, but is not limited to, the
departments of maintenance, planning, construction, research, and other
areas as necessary to include all necessary organization elements,” the FHWA
said. “The review should be tailored to the SHA’s existing programs,
policies, guidance, specifications, and organizational structure.
Information such as treatments used, the SHA’s mix of fixes, experience of
performance to date, etc. will be necessary for the review.” Each review was
anticipated to be 10 to 15 days over the duration of a two-month period.
Through the review of documentation, practices,
procedures, economic evaluation and historical performance information, PMS
information, and other sources, NCPP will assess the effectiveness of those
agencies’ pavement preservation programs in terms of pavement performance,
life, cost-effectiveness, and other measures, and evaluate what aspects of
the program or related areas of departmental operations could be refined or
improved to provide a more effective pavement preservation program. NCPP
will work with states to develop a roadmap of activities that can influence
the success of their pavement preservation program, the FHWA said.
Los Angeles’ only choice
Sometimes cash-flow problems mean a road agency has
no choice but to incorporate pavement preservation principles into its
program. That’s what the City of Los Angeles found recently as it
incorporated two strategies into its long-term pavement preservation
program: Rubberized asphalt slurry seals to prolong the life of its good
pavements, and foamed asphalt and asphalt emulsion base recycling for failed
pavements.
It’s all being driven by the need to make limited
funds go farther as the city grapples with maintaining and preserving its
6,500 miles of dedicated public thoroughfares (28,000 lane miles) and 800
miles of alleys in an area exceeding 466 square miles.
L.A.’s renewed interest in pavement preservation is
the result of California’s famous Prop 13, which dramatically cut taxes,
including resources used for street repairs and paving, said William A.
Robertson, director, Bureau of Street Services.
“We quit doing maintenance,” Robertson said at a
conference in January. “We quit doing slurry seal. The only thing we were
doing was resurfacing, and calling it maintenance. So for a number of years
— although we have the largest street system in the country — we were not
doing any true maintenance, and we suffered greatly. We saw a drop in
resurfaced streets from 275 miles a year to 118, because the money wasn’t
there.”
Over the last eight years the bureau has been able
to convince elected officials that the city needed to take a hard look at
preserving its transportation infrastructure. “We had to be innovative, and
look at different ways to turn around our preservation program based on the
little money that was available,” Robertson said.
And that soul-searching has culminated in a new
pavement preservation initiative that is based around rubberized slurry
surfacings for pavements to prolong the life of pavements in better
condition, and cold in-place recycling of failed pavements.
“We now are using CIP recycling and an expanded
slurry seal program simply to preserve the infrastructure we have in place,”
Robertson said, adding the city had no choice if it was to have an adequate
street system in the future. The city also continues to do asphalt overlays.
Understanding that any program savings can vanish
into municipal general fund, the base recycling machine — a 2200 CR from
Wirtgen America Inc., the first in the United States — was purchased by the
city council with a motion stating that any savings accruing from the use of
the machine must stay in the BSS budget for pavement preservation.
“The council put forward a motion instructing the
CAO for the city, telling him he could not touch that money,” streets
director Robertson said. “Any sav- ings created by this machine would go
right back into the preservation of our street system. That was a huge, huge
step for which we had been fighting for years. We have been innovative and
have thought outside of the box for years, but instead of being rewarded,
they have taken those savings from us and told us to do more with even less
money. But we now have the elected officials behind us, helping us preserve
more miles of pavement each year.”
PMS drives L.A. preservation
Los Angeles uses a pavement management system to
decide which streets will be reconstructed, which will be preserved with
rubberized slurry seal, and which will be maintained in some other way, for
example, crack-sealed, said assistant director of streets Nazario Sauceda.
“A PMS is a scientific, systematic, consistent
method for selecting maintenance and rehabilitation needs for determining
the optimal time of repair, by predicting future condition,” Sauceda said.
“In simpler words it’s a methodology that allows us to be cost-effective
when we manage our pavements, and a tool that we use to support our
decision-making.” L.A. uses the popular MicroPAVER from the U.S. Army Corps
of Engineers, which uses the Pavement Condition Index method for rating
pavements, complies with GASB 34, and is used by more than 600 cities,
counties, airports, and consulting firms.
GASB 34 is short for Government Accounting Standards
Board Statement 34, which requires that state and local governments include
the value of long-lived assets, including roads and bridges, in their annual
financial statements.
Pavement management “in the good old days”, he told
Better Roads, included routine maintenance cycles, priority on a worst-first
basis, which would be driven by citizen complaints and political priorities,
or recommendations by the old superintendent.
Modern PMS, though, are light years removed from the
old days, he said. They can be used to justify different funding level
requests, provide information to make efficient use of limited resources,
produce quantified and accurate data, track pavement performance, identify
current and future maintenance and rehab needs, select cost-effective repair
strategies, and predict future pavement conditions based on different budget
scenarios.
This PMS enables L.A. to determine which streets are
deserving of preservation with rubberized slurry surfacings, and which are
so far gone that preservation funds would be wasted. Those become
reconstruction candidates for full-depth base recycling. And a pavement
inspection and inventory is key.
“Our goal is to inspect all 6,500 miles in three
years, so each year we view 2,200 miles of streets,” Sauceda told Better
Roads. L.A. uses two semi-automated survey vans which take digital pictures
of pavements, which are analyzed for stresses. “Based on that information,
we calculate the PCI of the street,” Sauceda said. “Our qualified staff also
will conduct investigations by hand. Sometimes you may take a picture that
will not be accurate, so our guys will confirm the condition in person.”
The pavement condition is predicated on how
different distresses will impact street performance in L.A.’s mild climate,
but with rigorous traffic loadings, Sauceda said. “A PCI of 70 to 100, the
street will be very good to excellent,” he said. “40 to 70 is fairly good.
But with a PCI of zero to 40, the pavement will not be in good shape.”
Rubberized slurry seals
For streets not requiring complete reconstruction,
L.A. has adopted a rubberized slurry seal as a standard. This product,
called FlexSeal — manufactured locally by Petrochem Marketing, Inc. — is an
emulsion of oil, rubber, and fine sand. “It’s a preservative application or
sealant that inhibits oxidation of oils from the pavement, deters asphalt
cracking, and prevents water from seeping into the sub-base,” Sauceda told
Better Roads. “It extends the street’s serviceable life, thereby reducing
the need for repaving.”
The use of rubberized slurry seals has enabled L.A.
to expand its slurry program from 100 to 300 miles per year, and hire an
additional crew. The city also has fielded requests for information from
counties and cities in California, and Caltrans, in addition to cities from
Nevada to Texas to Wisconsin.
Despite the low cost and serviceability of
conventional slurry seals, L.A. chose to get out of that program due to
logistical problems. They required a base camp to be set up in local
neighborhoods, including as much as 50 to 100 tons of sand and aggregates,
plus stationing of large pieces of equipment for the duration of the
project, for as long as one month. There would also be environmental issues
of dust and noise pollution, noxious odors during mixing, daily equipment
maintenance, and its inability to consistently pass acceptable testing
standards.
“There would be a tremendous neighborhood impact
with our equipment,” Sauceda said. “We would store materials on-site, and
large pieces of equipment, and that causes a big problem in L.A., where
people are picky about their streets, their trees, and quality of life.”
Instead, the private-sector-produced slurry seal is
a premixed, rubberized material that is plant-mixed and delivered ready for
distribution on a project site. The material is distributed through PMI
applicator trucks under the direction of bureau forces. Furthermore, it’s
continually tested by the city’s Department of General Services Materials
Testing Laboratory, to ensure product compliance with spec. The testing is
out of the hands of the Bureau of Street Services.
Recycling failed roads
Today, L.A.’s bureau has retrofitted its two
municipal asphalt plants to increase their capacities to incorporate 20% of
reclaimed asphalt pavement into the asphalt manufactured at these plants.
The city also has a contract with a private sector supplier for a 50% RAP,
50% virgin plant mix, used in all phases of the city’s resurfacing program.
Cost savings drive this effort. The city recognizes
that RAP recycling results in a reduction in demand for virgin aggregates,
reduced construction time, less truck traffic and its environmental impact,
and overall reduced environmental impact.
But base recycling offers even more savings over
conventional reconstruction, said assistant director of streets Thomas W.
Thomas. By contrast, he said, conventional reconstruction involves
excavation and removal of existing material, transport of the material to
city-owned or private asphalt plants, and then importation, placement, and
compaction of new base materials and new asphalt concrete, with accompanying
prolonged lane closures and excessive truck traffic.
“We’re concentrating on our failed streets, with an
ultimate goal this year of saving $2.4 million a year based on a resurfacing
program of 150 miles, with an increase of 15 additional miles in FY
2005-2006 paid for from that savings, with no increase in the budget.”
L.A. is using the 2200 CR to do foamed asphalt
recycling throughout the city, and will be using it for emulsion
stabilization as well, Thomas said. Challenges in foamed base recycling
include the need for a minimum of 48 hours of dry weather, and maintenance
of liquid asphalt temperatures of 340 to 350 degrees F.
“The crew personnel assigned to the CIP program are
committed to a successful program and adapted very quickly to the new
technology, since they were experienced in cold milling and paving
operations,” Thomas said. “The division management and superintendent staff
are also committed to the CIP program and a team effort by everyone is
required for a successful program, including the support of the Department
of General Services, which develops the mix designs and provides testing
services.”
Foamed asphalt is created by carefully injecting a
predetermined amount of cold water into hot penetration-grade asphalt in the
mixing chamber of a pavement remixing unit, and offers a cost-effective
alternate for road base stabilization. Precise addition of water allows
control of the rate of asphalt expansion and the amount of expansion.
The expanded asphalt has a resulting high surface
area available for bonding with the aggregate, leading to a stable road base
using the existing in-place materials. The benefit is substantial cost
savings over use of asphalt emulsions for base stabilization, and complete
elimination of the cure or break period. The foamed base then is graded and
compacted, and can permit traffic — including heavy trucks — almost
immediately.
L.A. got a hands-on look at foamed asphalt
stabilization in the reconstruction of Mt. Lee Drive above Hollywood in
2003. Not only did the process result in a successful reconstruction, but it
eliminated an estimated 864 truck trips, greatly reducing construction
traffic, noise, and pollution through a mountainside residential area with
narrow, winding roads. The existing pavement was recycled to a depth of 6
inches, while applying 3% foamed asphalt (by mass). The new, completed base
was covered by a light tack coat, followed by surface brooming and
application of microsurfacing.
“We got a really good base out of it,” Thomas said
in January. “It’s been over a year and it’s held up through all the rains we
had over the winter.” Thomas estimated, in retrospect, that a conventional
rebuild would have taken 44 days and cost $400,000; but the foamed asphalt
rebuild was completed in just seven days at a cost of $100,000.
Nashville takes initiative
The combined city-county of Metro Nashville has gone
full-throttle in adopting and justifying to the public its pavement
preservation program. On its Web site, Metro Nashville defines its PMS and
then says how it will use it to husband its highways and make scarce dollars
go farther.
“A pavement management system is a computer-assisted
process that examines all public roads and determines the best means to
preserve and repair each road individually and the road system as a whole,”
Metro Nashville informs its citizens in a pavement preservation plan.
“Decisions are based on pavement condition, ride quality, costs of
treatment, benefits to the road, and benefits to the road system. Because
maintenance funds are always limited, the management system recommends the
optimum sequence of repairs to make the best use of taxpayer dollars. The
system provides a fair and equable way to compare repair needs in all the
city’s neighborhoods to ensure the decisions are in the community’s overall
best interests.”
Like L.A., Metro Nashville public works uses
specially-designed digital survey vehicles to photograph every public street
in Davidson County. Trained technicians then view sections of a road to
determine the amount of pavement damage, using a uniform scoring method.
Measuring devices mounted on the vehicle also record the amount of rutting
in the pavement and evaluate the ride quality. All this information is
stored on a computer for processing using specialized pavement management
software configured for Nashville’s needs.
“MPW scores the streets in two categories — pavement
stress and ride quality — to obtain an overall score for the street.
Pavement distresses include cracks, potholes, and ruts,” Metro Nashville
says. “Ride quality is the measure of how bumpy a road is. The scores help
public works officials determine the best strategy for each street. One
location may need a complete overlay while another street may only need some
cracks repaired and potholes filled. By tailoring the repair decision to the
needs for each street, based on the data collected, MPW can stretch tax
dollars further while making the best repair decision for each street.”
That’s the very definition of pavement preservation.
Echoing classic pavement preservation philosophy,
Metro Nashville says, “The secret to good pavement management is repairing
roads that are still in fair condition but experiencing the early stages of
pavement distress, reduced ride quality, and rutting,” MPW says. “By keeping
those roads in good condition with lower cost repairs, MPW will still have
money for reconstructing a few roads each year that are in the worst
condition. A dollar in road repair spent early can give the same improvement
as four dollars spent later in the road’s life when repairs are more
expensive. If funds are spent only on the worst roads, our community will
stay in a cycle where we can afford only to reconstruct a few roads in very
poor condition each year while neglecting simple, lower cost repairs on
other roads. If we concentrate on the worst roads, we will never catch up.”
ERES Division of Applied Research Associates, Inc.,
is Metro Nashville’s pavement management and preservation consultant. |
