| Asset management is a systematic process used to maintain, upgrade, and operate physical assets cost-effectively. Managing transportation assets in this manner is not a new concept. For example, state highway agencies have developed and used pavement, bridge and maintenance management systems for a couple of decades. These systems have typically operated without linkages among them, however, and without a clear connection to resource allocation and other agency processes.
What is new with transportation asset management is a strategic, business-oriented approach to what has been a fragmented, reactive, tactically driven field. While the original motivation was to increase agency effectiveness, asset management also serves to:
- Reduce the material resources needed to support the maintenance and operation of
- transportation facilities
- Account for impacts upon transportation facility users during and after work is done on a road
- Adjust maintenance and operations practices to reduce these impacts.
Thus, asset management is a strong contributor to achieving sustainable highways. In fact, it is integral to the economic efficiency part of the triple bottom line and supportive of environmental as well as social objectives. To demonstrate this point in specific, quantitative terms, the application of life-cycle cost analysis to highway pavement management is discussed below.
Life-Cycle Cost Analysis
Life-cycle cost analysis (LCCA) is an important tool that is used to evaluate the long-term economic efficiency of competing investment options. In defining “long term” for pavement projects, the Federal Highway Administration (FHWA) recommends an analysis period of at least 35 years. This extended analysis period, much longer than in traditional methods, clearly supports the goals of sustainability.
Properly applied, LCCA is comprised of two cost categories: agency costs and road user costs.
Figure 1: Additional Surfacing Placed Before Failure (Source: Doyt Boiling, Utah Technology Transfer Center, Good Roads Cost Less – An Asset Management Approach for State, County and Local Government, 2001) |
Figure 2: Additional Surfacing Placed After Failure (Source: Doyt Boiling, Utah Technology Transfer Center, Good Roads Cost Less – An Asset Management Approach for State, County and Local Government, 2001) |
Agency Costs. Agency costs are the stream of costs incurred over the analysis period. They are estimated in constant dollars and discounted to the present using a real discount rate. The point is to identify maintenance strategies and pavement designs that minimize the net present value of this cost stream.
A key tenet of asset management is that a program of early interventions taken before pavement failure will minimize the cost stream. Pavements tend to deteriorate over time following a classic “S-curve,” and the most effective interventions occur before traversing down the steep part of the curve. Consider, for example, Figures 1 and 2 (Figure 2 on the following page) illustrating two alternative points of intervention. Figure 1 illustrates a pavement resurfacing project that occurs prior to pavement failure. A 50-mm (2-inch) overlay extends the pavement life by approximately one million axle applications. In contrast, the Figure 2 resurfacing project occurs after pavement failure and a 145-mm (5 3/4-inch) overlay is required to accomplish the same extension of one million axle applications.
The example shown in Figure 2 not only leads to additional costs, in a sustainability context it also requires additional materials and, hence, additional natural resources. The additional 95 mm (3 3/4 inches) translates to more than 17 tons of additional aggregate and binder per lane mile.
Replicated across the country, post-optimal interventions require the unnecessary application of substantial amounts of material each year.
Road User Costs. Road user costs comprise three categories: vehicle operations, delays and accidents. Each of these three cost categories may be calculated for two conditions:
- • Increased costs during the resurfacing/reconstruction project(work zone effects)
- • Long-term costs during the ongoing operation of the highway.
While each of the six cells in this three-by-two matrix would have a calculated value, the most significant user costs are delay costs associated with the work zone (delay costs can account for more than 95 percent of work zone road user costs) and long-term vehicle operation costs (VOC). In this overview article, the discussion is limited to these two cells.
Work Zone Effects: User Delay Costs. The traditional approach to pavement management projects has been to generally disregard, or at least not quantify, the user costs generated by project work zones. This omission clearly unbalances the analysis and can lead to suboptimal decisions on project design and scheduling. In contrast, asset management principles support a rigorous analysis of work zone effects on road user costs, particularly delay costs—which can become immense in a congested urban environment.
Analysis suggests that delay costs in a forced flow situation can easily exceed $500,000/day on a heavily traveled urban freeway. At this level of impact, practically any increased agency cost can be justified if it materially reduces the duration of the project. This realization has led many agencies to be cautious in the application of work zone delay costs to project design. Nonetheless, FHWA has sponsored the development of QuickZone, an easy-to-use analytical software tool that supports quick and flexible estimates of work zone delays, and it is encouraging state departments of transportation to take these costs into account in the planning, design and operation of work zones.
Road user delay cost estimates can be used to derive estimates of air emissions, fuel consumption and health impacts. This would be a useful topic for further research that would support the presentation of results in the context of economic, environmental and social outcomes.
Long Term Cost: VOC. In addition to reducing agency costs, timely pre-failure interventions result in smoother pavements, and smoother pavements reduce VOC. These cost reductions are principally in the area of reduced fuel consumption and, thus, are directly pertinent to the sustainability perspective.
Asset management calls for a comprehensive assessment of all costs and, from this perspective, VOC are considerably larger than agency costs. One calculation suggests that in estimating total costs for a typical highway segment during its design life, VOC are approximately seven times greater than agency costs; thus, any improvement is significant.
A specific quantification of the improvement in VOC caused by smoother pavements has proven difficult due to a lack of real-world data. Perhaps the most authoritative calculation is derived from a recent experience at WesTrack, an accelerated pavement test facility in Nevada sponsored by FHWA. WesTrack uses four driverless trucks to accomplish repetitive pavement loadings to test the validity of new Superpave mixture design procedures.
During two and a half years of testing, these trucks traveled more than 1.3 million km (800,000 miles) and applied 4.9 million equivalent single axle loads, after which various pavement sections exhibited varying amounts of roughness, rutting and/or cracking. A major pavement rehabilitation project was then performed at the facility.
The distinct differences in pavement condition immediately before and after rehabilitation provided a unique opportunity to precisely measure the effect of pavement condition on VOC with other variables held relatively constant. The rehabilitation project reduced the average International Roughness Index (IRI) by at least 10 percent and heavy truck motor fuel mileage improved by 4.5 percent. Extrapolating that improvement to a truck fleet operation of 1.6 million vehicle km (nearly 1 million vehicle miles) per year, an annual fuel savings of over 38,000 liters (nearly 10,000 gallons) would be achieved. Also, there was a dramatic reduction in the frequency of fatigue failures of truck and trailer components.
Perpetual Pavements
Perhaps the fullest realization of the application of asset management principles to pavement design and management is embraced by the concept of perpetual pavements. The idea is that a combination of robust design (full-depth deep-strength pavements), recent developments
in material mix and selection, and an aggressive preventive maintenance program (including thin overlays for the riding surface) can achieve very long term performance for pavement structures—greater than 50 years. This concept has been promoted primarily as a method to reduce agency cost, which is a noteworthy goal; however, from the perspective of sustainable highways the curtailment of periodic reconstruction projects and the continued provision of smoother pavements also can serve to save material resources, reduce fuel consumption and minimize user delays.
In 2001 the Asphalt Pavement Alliance initiated an annual program of perpetual pavement awards to encourage the further development of this concept. Its 2003 awards were presented to six state departments of transportation (Arizona, Minnesota, Missouri, Nebraska, Ohio, and Oklahoma), the New Jersey Turnpike Authority and the City of Toronto, Canada in recognition of pavement structures dating back to 1950.
This concept is addressed also in the re-authorization of the U. S. federal transportation program currently pending before Congress. HR. 3550 proposes the authorization of a “Highways for LIFE pilot program” to encourage the development of long-lasting, high-quality, cost-effective highway projects.
Asset Management and Sustainable Highways
While the example discussed above was applied to pavements, the same principles apply to virtually all aspects of highway work—bridges, drainage structures, traffic control devices, pavement markings, etc. In addition, when improved technologies and processes for recycling materials and reducing the disruptive aspects of road improvement are incorporated into the engineering analyses, an asset management approach is an important analytical tool that strengthens our ability to deliver sustainable highways. |
