Month: July 2015

Prepared by Vivek Khanna, KSA Engineering

 

Introduction

The highway infrastructure of the United States consumes 17 percent of its Gross National Product (FHWA, 2006) and has been created over the years at a tremendous cost. Forster (2004) and the Federal Highway Administration (FHWA, 2007) estimate the value of this national transportation infrastructure at $1.75 trillion. The interstate highway system is now more than five decades old. With this aging, the emphasis of the transportation community has shifted from building new infrastructure assets to maintaining and improving the existing assets. FHWA’s online resource center (2007) claims that the total annual capital outlay to preserve and improve the highway system is more than $139 billion.

There has been a nearly 45% increase in total annual expenditures on highways by Federal, State, and local governments from 1997 to 2004 (FHWA, 2006). In 2004 the total expenditures including funds expended for debt retirement, administration, highway patrol, physical maintenance, and capital expenditures amounted to $147.5 billion. Capital expenditures alone on highways rose 45.2%, from $48.4 billion in 1997 to $70.3 billion in 2004 (FHWA, 2006). Resurfacing, rehabilitation, or reconstruction of existing highways and bridges, consumed 51.8% of the total capital budget in 2004. The net effect of the increase in capital investment and the changed focus of improvement efforts has resulted in a 58% increase in spending on highway and bridge rehabilitation ($23.0 billion in 1997 to $36.4 billion in 2004). Investment in construction of new roads and bridges and the widening of existing roads attracted lower funding during this period, rising only 28% from $21.5 billion in 1997 to $27.5 billion in 2004 (FHWA, 2006).

Vast sums of money are therefore spent every year towards the maintenance, rehabilitation (MR) and enhancement of this transportation infrastructure that is vital to the economic health of the nation. Despite the healthy increases in governmental spending on highways, the resources deployed to maintain conditions and performance has increased only marginally in current dollars and has actually declined in terms of real dollars. Added to this, escalating global energy prices are fueling large increases in construction costs. It is therefore important to develop tools to aid administrators faced with ever shrinking budgets and greater accountability, in effective utilization of resources to maximize pavement network serviceability.

Pavement management systems (PMS) provide a systems approach to pavement maintenance management. PMS’s use sophisticated decision making algorithms to assist in the development of prioritized capital improvement programs (CIP) that lead to optimized pavement condition and maximize network serviceability within the imposed budgetary constraints.

The General Accounting Office (GAO, 1998) in its review of current and future levels of Airport Improvement Program (AIP) funding had this to say –
“The National Priority System, FAA’s primary method for determining which AIP grant applications from individual airports should be funded, establishes a priority rating on the basis of factors such as the purpose and type of the project. Runway rehabilitation projects fare well in this system and are typically funded ahead of most other types of projects. Most applications for such projects received funding in fiscal year 1997, according to FAA officials. However, local FAA officials said that they forward only those applications they are relatively certain will be funded. FAA’s priority system is not well equipped to determine which proposed rehabilitation projects will deliver the best return for the dollars spent. Waiting to rehabilitate a runway until the pavement has seriously deteriorated can mean that rehabilitation will cost 2 to 3 times as much as it would have if rehabilitation had occurred earlier. The key to identifying the best time to conduct rehabilitation is having comprehensive knowledge of pavement conditions. Currently, fewer than half of the airports in the national system have information systems that will provide this knowledge. Furthermore, when allocating Airport Improvement (AIP) funds, FAA does not evaluate the cost-effectiveness of the rehabilitation projects it approves”.

In its report GAO (1998) recommended that the Federal Aviation Administration (FAA) require all airports in the national airport system (NAS) to submit index ratings on pavement condition on a regular basis and use this information to create a database on pavement conditions for evaluating the cost-effectiveness of project applications and forecasting anticipated pavement needs.

Historical view of PMS development

The concept of pavement management as a tool for maximizing utilization/serviceability of a network of pavements with the deployment of optimal resources dates to the 1960s. Some engineers consider the American Association of State Highway Officials (AASHO) road tests (1956 – 1960) as being the origins of the systems approach to pavement maintenance. As a result of the tests, it was postulated that pavement performance could be described independent of pavement type. In 1966, a study was initiated to arrive at an understanding of the AASHO road tests. Expanding on this study, Hudson (1968) started work on a systems approach to pavement design and maintenance. Wilkins (1968) led Canadian efforts at developing a systems approach to pavement management. Scrivner (1968) of the Texas transportation Institute presented a systems approach to flexible pavement design.

By the late 1960s, the term “pavement management system (PMS)” had been coined and was in use to describe a systems approach to pavement design and maintenance. One of the earliest attempts to translate the systems concept into a working schema was a result of Texas Department of Transportation’s (TxDOT) Project 123 (Hudson, 1970). This study pioneered development of many of the techniques of pavement management. The National Cooperative Highway Research Program’s (NCHRP) project 1-10 (Hudson, 1973) presented a working methodology for pavement management. The US Army Construction Engineering Research Laboratories (USACERL) with funding from the FAA, American Public Works Association (APWA), Federal Highway Administration (FHWA), US Air Force Engineering and Services Center (AFESC), US Navy and US Army Corps of Engineers (USACOE) released the first version of USACERL’s PMS in 1981.

The PMS concept demonstrated the need as well as the benefit of a systems approach to not only pavement design but to the construction and periodic maintenance of pavements as well. Figure 1 reiterates the rationale behind pavement management. It explains that the premise of a systems approach to pavement management is that “for every dollar spent on managed pavements, agencies can save between three to six dollars in reduced pavement maintenance costs”.

 

The FHWA-University of Texas-HRB conference on structural design of asphalt pavement systems in 1970 made it clear that PMSs were here to stay. The American Association of State Highway and Transportation Officials (AASHTO) issued their guidelines for pavement management systems in 1985. These guidelines contained minimal suggestions for developing and implementing a PMS. AASHTO (1990) later issued more detailed guidelines in 1990. Then in 2001, AASHTO (2001) issued comprehensive, guidelines identifying the state-of-practice in pavement management. These guidelines provide a good PMS implementation procedure and describe the typical components of a good PMS.

Zimmerman et al. (2000) summarize that PMSs are expected to form a vital part of decision making for managing and maintaining the transportation infrastructure. Pavement managers must address their transportation needs in this era of soaring construction costs and shrinking budgets while at the same time be held to ever greater scrutiny in their efficiency in the expenditure of taxpayer money. As a result, the importance of infrastructure management systems (IMS) to assist with effective allocation of these resources to manage infrastructure assets becomes more critical than ever. The systems approach has created a realization in the stakeholders that the challenge of managing and maintaining existing transportation infrastructure under today’s environment is more difficult than the design and construction of the initial system, when there was less scrutiny of public expenditures.

As per Thomas (1995), infrastructure in the United States and the world is aging. Pavement engineers and transportation managers are increasingly aware of the need to assess the condition of this vital asset. However, finite budgets limit the replacement of assets. It is therefore imperative to accurately asses the condition of and damage to transportation infrastructure.

 

For more information, please contact Dr. Vivek Khanna at: vkhanna@ksaeng.com

 

References:

• AASHTO, “Pavement management guide”, Washington D.C., 2001.
• FHWA, “Status of the Nation’s Highways, Bridges, and Transit: 2006 Conditions and Performance Report”, http://www.fhwa.dot.gov/policy/2006cpr/hilights.htm, 2006.
• FHWA, “Online resource center – Asset Management Guide”, http://www.fhwa.dot.gov/resourcecenter/teams/finance/fin_1amg.cfm, 2007.
• General Accounting Office, “Keeping Nation’s Airport Pavements in Good Condition may require substantially higher Spending”, GAO/RCED-98-226, Washington D.C., 1998.
• Hudson, W. R., Finn, F. N., McCullough B.F., Nair, K. and B.A. Vallerga, “Systems Approach to Pavement Systems Formulation, Performance Definition and Materials Characterization”, Final Report, NCHRP Project 1-10, Materials Research and Development, Inc., March 1968.
• Hudson, W. R., and B. F. McCullough, “Systems Approach Applied to Pavement Design and Research, Research Report 123-1”, Center for Transportation Research, The University of Texas at Austin, March 1970.
• Hudson, W. R., and McCullough, B. F., “Flexible pavement design and management, National Cooperative Highway Research Program Report”, No. 139, 1973.
• Scrivner, F.H., Moore, W.M., and McFarland, W.F., “A systems approach to the flexible pavement design problem”, Research Report 32-11, Texas transportation Institute, Texas A&M University, 1968.
• Shahin, M. Y., “Pavement management for airports, roads, and parking lots”, Kluwer Academic, Dordrecht, The Netherlands, 1994.
• Thomas, G., “Overview of nondestructive techologies”, Proceedings of the international society for optical engineering, Volume 2457, 5–9, 1995.
• Wilkins, E.B., “Outline of a Proposed Management System for the CGRA Pavement Design and Evaluation Committee”, Proceedings Canada Good Roads Association, Ottawa, 1968.
• Zimmerman, K.A., Botelho, F. and Clark, D., “Taking Pavement Management into the Next Millennium, Transportation in the New Millennium: State of the Art and Future Directions”, Perspectives from Transportation Research Board Standing Committees, Transportation Research Board, 2000.

Prepared by David Humphrey, Ohio Department of Transportation

The Ohio Department of Transportation (ODOT) is implementing a near-project level pavement management system.  One of the key elements that made the system possible is our rich history of detailed distress data.  In the early to mid 1980’s, ODOT developed a pavement condition rating (PCR) system.  The PCR is based on a visual inspection of the pavement and rating the distresses for both severity and extent.  ODOT has used the PCR to rate all state maintained roads on an annual basis since 1986.

The PCR consists of up to seventeen distresses with a maximum deduct value for each distress resulting in a zero to 100 value, with 100 being the best condition.  Unique distresses exist for each pavement type: flexible, composite, and jointed concrete (Ohio no longer has any exposed continuously reinforced concrete).

To maintain consistency, a manual was developed explaining each distress type, the different extents, and the different severity levels with pictures of representative distresses.  In addition, we have used a small group of permanent employees to do the ratings over the years.  Currently the entire state is rated each year by three raters, each with over 20 years of experience.

Using the long and detailed distress history, we were able to develop performance curves for each distress for each of the typical pavement construction and maintenance activities (chip seal, micro surfacing, overlays, complete replacement, etc.).  With the distress performance prediction curves, we were able to develop detailed decision trees as the basis for the pavement management system.

While the experience of the raters is a great asset, with all of them nearing retirement eligibility, it has also become an area of great concern.  To prepare for possible retirements, ODOT initiated a research project to see if an automated system could reproduce our PCR.  Three vendors participated in the research and in the short time available, none was able to do better than a 20 percent match of the manually rated PCR.

ODOT is continuing to work with one of the vendors to try and improve the automated collection.  The hope is we may be able to get a nearly 80 percent match with the manual ratings.  Some distresses, particularly at the low severity levels, are very difficult for the automated systems to detect with current technology.  Our hope is the technology will continue to improve.  In the meantime, we are faced with the possibility of converting to a new PCR.  If we are able to collect both manual and automated PCR concurrently for a sufficient number of years, we may be able to develop a correlation between the two.  If not, we are faced with the prospect of losing all our historical PCR data and the performance curves developed from that data.

Automated distress collection is safer for the raters, may be required by federal reporting requirements, provides data for mechanistic-empirical pavement design, and should improve with time, rather than retire.  ODOT faces some big challenges if we are to change the way we’ve been doing business for the last 30 years.

 

For more information, please contact David Humphrey at David.Humphrey@dot.ohio.gov

By Edgardo Block, Connecticut Department of Transportation

One of the key findings of applying optimization methods to the problem of investing in pavement networks to meet certain objectives over an appropriate time horizon is that the worst-first intervention strategy is generally not the most effective, at least using a benefit-to-cost criterion. There is ample evidence of this, perhaps most strikingly exhibited by the experience of the Kansas Department of Transportation as it implemented this philosophy (see chart below).

(Note:  this chart has been copied and pasted from the presentation hyperlink above).

In order to achieve these results, however, it is necessary to provide an investment level that is sufficient to address the backlog of roads in poor condition using a pavement-management approach.

A relevant question is what happens when we implement a pavement-management driven investment strategy but the level of investment is not sufficient to prevent roads from falling into the “Poor” category.  If it is true that maintaining roads in better condition provides better return on investment, it follows that the optimized strategy favors these projects to the detriment of addressing the roads in worst condition. This is borne out on the following charts, of average condition and condition distribution, drawn from an actual budget scenario for a transportation agency.  The scenario achieves the goal of maintaining current network pavement condition over 15 years (actually, it marginally improves it): While average condition is maintained, the percent of length in “poor” condition increases from just over 1% in 2014 to almost 16% in 2029.

 

In this case, this makes me feel good about how my pavement-management system is working — but there is still the reality of an increasing length of pavements in poor condition that results from this management approach.  This feature of the optimized strategy – how well the traveling public is prepared to deal with increasing lengths of poor pavements – has to be addressed somehow. At best, the road users could get used to these conditions if they understand the higher rate of return on investment of the optimized strategy.  However, if the transportation system customers are not willing to be subjected to these poor conditions, this could create a backlash with the end result that the (demonstrably) more effective strategy is abandoned.

There are two questions that, if answered, can be of great use in supporting the optimized strategy under such a constrained-funding scenario:

1.  What are the results of the same level of funding but using a worst-first approach?

2.  How can “poor” roads be addressed without abandoning the optimized strategy?

A Pavement Management System can provide an answer to the first question by limiting interventions to those at lower condition levels. In the state DOT example above, a reconstruction-only strategy over the same period and at the same investment level leads to 37% poor roads at the end of 15 years– and in the above example, non-pavement-related costs are excluded, so the result is likely to be much worse if right-of-way, maintenance-of-traffic, and other project complexity is built into the forecast.

(These two graphs were obtained by using the same $140M investment level as the optimized strategy, but limiting treatment options to “capital improvement” projects, i.e. reconstruction, rubblization, full-depth reclamation.)

Based on traditional practice, however, the strategy is not likely to be to reconstruct but to apply some remedial treatment that would be less costly but achieve some improvements. The result in that case would be to arrive to a state of “network mediocrity,” probably still with a significant length of roads in poor condition.  This can also be simulated with a pavement management system by adding a remedial treatment with its own expected performance model and treatment application rules. The most negative implication of this approach is that the structural backlog of pavements is not addressed at all, making it that much more difficult to ever improve network conditions beyond that mediocre state achieved – doing that would entail major rehabilitation or reconstruction of the majority of the network.

The answer to the second question gets to the point of my post: Let’s say that, like me, you as pavement manager have not set up such a remedial treatment in the Pavement Management System. It is still possible to estimate the required effort to deal with the “poor-road backlog” by looking at PMS output.  This can be done by applying a unit cost and expected duration to a “typical” remedial treatment. Assuming that all poor roads are unacceptable to “road customers,” it is possible to use the miles of poor pavement (lane-miles, preferably) and an expected remedial-treatment duration to assign a cost to achieving this objective of addressing poor roads. At the end of the life of the treatment, a subsequent remedial treatment would have to be applied, to the end of the analysis period. In the case above with a 15-year analysis period, and using a remedial treatment lasting 5 years, the roads that are listed as poor in the initial years would receive up to three remedial treatments. Estimating program size to control the length of pavements in poor condition then becomes an accounting and engineering-economics exercise solvable in Excel.  To get the number of miles required each year the new poor miles are added to those for which the remedial treatment duration has expired; the program costs can be brought to present values or to an equivalent annual uniform cost and then the funding source can be sized appropriately.

A major caveat is that unless funding for this remedial program is provided from a separate source, this will take away funds from an optimized strategy, thus reducing the ability to achieve a network objective such as maintaining current network condition. An iterative process of adjusting (reducing) the optimized funding and recalculating the size of the remedial program is going to be required to develop actual condition targets. And, as always, project-level pavement evaluation and management have to be part of the equation to arrive at the actual projects delivered with such a program.

Lastly, it must be stressed that there is no panacea in the remedial-treatment management of poor roads: they will still require major investments for their condition to be improved. But what an explicit remedial-treatment program can do is minimize the amount of funding allocated to a worst-first strategy while maintaining the optimized strategy, which is where the real return on investment is. Ideally, the remedial treatment, with costs and performance predictions, would be built into the pavement management system. If – like me – you are not quite there yet, it is still possible to use your PMS to provide a reasonable approximation.

 

For more information, please contact Edgardo Block at Edgardo.Block@ct.gov