Pavement Preservation Compendium II
Pavement Preservation Fights for Respect
by Tom Kuennen
Six years after the creation of the Office of Asset Management within the Federal Highway Administration, 13 years after the establishment of the Foundation for Pavement Preservation, and two years after the founding of the National Center for Pavement Preservation, the concept of pavement preservation still faces a tough climb to full acceptance.
While many county and city road agencies maintain pavement inventories and pavement management systems, not all have been able to integrate the pavement management system with a preservation program that will show where dollars will be best spent toward riding surface longevity.
Classic pavement preservation starts with a pavement inventory and condition database, which is used to establish which road surfaces are near the point at which they will begin to fail rapidly. Those pavements - not the worst pavements favored by politicians - are the ones that should be targeted with whatever funds are available, prolonging their service life to a degree not possible otherwise.
But a problem arises for the road manager. To spend money where it will do the most good, pavements that are falling apart should not receive maintenance dollars, but should be allowed to fail and then be rebuilt. That's why adhering to a pavement preservation program may put a road administrator in conflict with elected officials, who may demand quick fixes for failing pavements.
At that point, the pavement inventory and pavement management system can be exhibited to show that the road administrator is doing the right thing. The inventory and PMS provide cover for both the administrator and elected official in supporting pavement preservation principles.
"The worst way of responding to complaints is the policy of worst-first," said John O'Doherty, P.E., training coordinator, National Center for Pavement Preservation. "It's a suboptimal strategy and, if you continue to follow it, you'll eventually bankrupt your agency. When you wait for worst-first, you've waited until structural damage is being done to the road and you have to do major rehabilitation. Worst-first waits until serious damage is done, and every road in your system will have to descend to that level, making it the most expensive strategy you can think of."
Worst-first is seductive politically, though, O'Doherty told Better Roads. "It's very appealing politically," he said. "If you're an elected official, or department director, it's reassuring to the public to have them hear that you are doing the worst roads first, because they will get a warm, fuzzy feeling. But it's a terrible policy."
"Each highway agency faces different challenges in applying pavement preservation treatments and establishing an effective preservation program," said David R. Geiger, P.E., director, FHWA Office of Asset Management, in a May 2005 memo promoting pavement preservation. "Preservation involves a paradigm shift from worst-first to optimum timing. Preservation programs must focus on demonstrating benefit, securing commitment of top agency management, convincing the public, and selecting the right treatment for the right pavement at the right time."
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).
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 savings 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."
Township Preserves Roads - and the Budget
A rural township west of New York City is making its limited road budget go further by rigorously preserving pavements with polymer-modified fiber-membranes and paver-placed, ultra-thin surface treatments, prolonging pavement life and satisfying its new commuter residents who demand smooth pavements.
The Town of Minisink, located just north of the New Jersey border in Orange County, about 55 miles from Manhattan as the crow flies, is a rural jurisdiction now being populated by commuters who can drive to nearby rail and bus stops for their daily journeys to New York City. As such, increased demands are being placed on the 102 lane miles of town roads which could lead to their destruction, if not for the pavement preservation practiced by the town.
In July, Minisink was surfacing what it considered to be some of the worst roads in the town, but anywhere else they would not appear to be in such bad shape. That's because the town has actively been preserving its pavements for years.
"We don't want the cracks to get any worse, and we don't want the base to fail," said Randy Filipowski, highway superintendent, Town of Minisink, New York. "We find that this surfacing process cuts reflective cracking at almost 90% over the last three years on roads where we've used it. It works out well and offers a good bang for your buck. We're the smallest town in Orange County, with the smallest budget, and we have to make our money stretch."
In July, contractor Midland Asphalt Materials was placing FiberMat surfacing on a number of roads in Minisink. The fiber-membrane process suppresses reflective cracking, preserves the pavement, and provides a permanent riding surface that can stand on its own, or it can be surfaced later with NovaChip, or a hot-mix asphalt overlay.
"The fibers form a mesh within a double seal, which bridges the cracks," Filipowski said. "As everyone in the highway industry knows, the object is to keep water out of the base, and to keep the fines from moving around. Catching the cracks at an early stage like this, where they're only 0.25- to 0.375-inch deep, stops the road from coming apart. We want to seal before chunks start coming out of the road, so we don't have to patch."
The surfacing used there consists of 2.375-inch-long fibers that are individually cut and randomly dispersed into the first layer of a special CRS-1P type polymer-modified emulsion sprayed by the specialized trailer unit. That layer is immediately topped by another emulsion spray, which covers and encapsulates the fibers, sealing them in, all in one pass. The tanker and specialized trailer unit can move forward rather quickly, with typical speeds of 250 to 300 feet per minute. A standard chip spreader then applies the aggregate.
The FiberMat surface being placed in Minisink will be used as the driving surface until the season of 2006, when it will be overlaid with NovaChip ultra-thin surface treatment from Sem Materials; thus it will serve through the winter as a driving course, then next year as a stress-absorbing membrane interlayer.
The reason is that the town simply can't afford to do both surfacings at the same time, so it works incrementally, confident that the fiber-membrane will serve all winter until overlaid in the spring. "Use of the FiberMat followed by NovaChip costs less money than asphalt overlays, and we get the SAMI function as well," Filipowski said. "This process allows us to resurface up to 6 miles of roads a year in this fashion."
Enhanced aggregate retention
The thickness provided by the fibers and twin emulsion layers also enhances chip retention. "The chip is imbedded in the emulsion, which has bonded to the fibers," said Daniel J. Koeninger, P.E., Midland Asphalt Materials Inc. "When the aggregate chip is under stress due to traffic, the emulsion and fiber provide tensile strength to retain the chip."
The fibers make it unique, Koeninger said. "There is no other product that gives this kind of coverage. There is no comparison with non-woven/needle-punched overlay fabric, because it's usually applied in a manner where it cannot fulfill its purpose. There will be bunching, tears, and wrinkles around curves, and they all reflect back to the surface. Also, this product can be installed directly on a milled surface."
In the Town of Minisink, the FiberMat SAMI was dosed at a rate of 0.16 pounds of glass fibers per square yard. The modified asphalt emulsion was applied in two simultaneous applications which total 0.4 to 0.5 gallons per square yard depending on surface and conditions. A quarter-inch top-sized stone was placed on the sprayed membrane to blind-in the surface before an overlay is placed at a later time.
When the process is used as a wearing course seal, the glass fibers are applied at a lesser rate of at least 0.11 pounds per square yard, depending on the severity of the cracking. The membrane sandwich is followed by placement of 0.25-, 0.375-, or 0.5-inch top-sized aggregate, or a mix of those sizes as in a double dressing.
For either formulation, the chips are seated into the surface by a pneumatic tired roller, and the pavement opened to traffic in a quarter-hour. "With this process we don't keep anyone out of their homes or stop them from going anywhere," Filipowski said. "Very seldom will we close a road."
The application unit is improved over the configuration available just a year ago. "The fiber capacity has been increased four-fold," Koeninger said. "The fiber machine can go farther before having to reload fiber. The efficiency of the new cutting unit allows the material to be deposited more rapidly. As a result it can potentially do up to 70,000 square yards per day, depending on site conditions." The machine is towed by a tanker or an ordinary distributor. "The new machine lays the fiber out very uniformly and even," Filipowski said. "They've come a long way."
Voters demand a black finish
While the township has the option of using the process as a permanent, stand-alone driving surface - instead of the other overlays - Filipowski won't do it. "We're only an hour out of Manhattan, and the people moving in are used to blacktop or concrete roads, and they're really not enthusiastic about oil and chips," Filipowski said. "The NovaChip is a very good intermediate process between HMA and oil and chip, so we do the fiber process first, and place NovaChip on top later."
And because the township road superintendent is an elected position, providing good roads, surfaced the way the voters like, is paramount for Filipowski, who faces election soon. "It's our third year with the process, and we're happy," he said. "They haven't hung me yet. Until something better comes along, we're going to stick with it."
Information for this article contributed by Midland Asphalt Materials Inc.
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.
For More Information
A vast amount of information on pavement preservation is available to pavement professionals, and it's growing faster and faster. Here are some places to start:
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."
|"Preservation involves a paradigm shift from worst-first to optimum timing. Preservation programs must focus on demonstrating benefit, securing commitment of top agency management, convincing the public, and selecting the right treatment for the right pavement at the right time."|
ERES Division of Applied Research Associates, Inc., is Metro Nashville's pavement management and preservation consultant.
Reprinted from Better Roads, September 2005.