Long-Term Pavement Performance Program Highlights: Accomplishments and Benefits 1989-2009

RETURN on INVESTMENT

Colorado Implements Proven PCC Pavement Practices

The Colorado Department of Transportation (DOT) has been a strong supporter of LTPP by being proactive in examining performance at its LTPP test sections and making improvements based on these evaluations. A 2006 report¹⁹ documented the implementation of improved PCC pavement practices based on LTPP test sections. The LTPP data confirmed that widening a slab from 12 ft to 14 ft (3.7 m to 4.3 m) provides the structural equivalent of increasing slab thickness by 1 in. (2.5 cm); and that a single 1/8-in. (0.32-cm) cut is as effective as Colorado DOT's previous standard 3/8-in. (0.95-cm) double cut for PCC joints, thereby providing a savings of $0.57 per linear foot of joint ($1.87/m). These results were derived from the SPS-2 and SPS-4 projects, respectively.

Many aspects of the LTPP program that are clearly beneficial to the highway community are difficult to quantify monetarily—such as procedures for QC/QA for research-level data collection, data collection techniques and practices, test methods, and database management. Other programs are benefiting from the extensive experience of the LTPP program, as well. For example, plans for the Long-Term Bridge Performance Program emphasized lessons learned in LTPP: the importance of standardizing data collection procedures and documenting data cleaning and analysis in rigorous reports. The plan also recommended using the LTPP program as a model for organization structure and oversight.²⁰

Other aspects of the LTPP program can be defined monetarily as cost savings recognized through implementation and can serve as a basis for determining the return on investment of the LTPP program.

LTPP by the Numbers

The numerous innovations that have directly resulted from the LTPP program—procedures, software tools, manuals, and research findings—have been implemented across the United States and abroad. A partial listing of LTPP resource statistics is shown in table 2.

Opportunity Cost

From an agency perspective, cost savings do not contribute directly to an increased bottom line, but rather to an optimized opportunity cost. Almost invariably there are significantly more projects to be completed than funding will allow. Funds that do not have to be used on one project can thus be shifted to another. As an example, the design of a project in Arizona was being based on existing tables of equivalent single-axle loads. However, because of the presence of an LTPP WIM site, measured traffic data were available. These data clearly showed traffic loads to be much less than the design table indicated. This resulted in a cost savings of more than $2 million for the project—extra funds that could then be allocated to other priority projects. Nationwide, these "save/extra" moneys serve to improve the overall pavement network without incurring additional costs.

"The true benefit of the LTPP database will come from its use in developing new pavement designs and methods for building and maintaining pavements."

Preserving and Maximizing the Utility of the Pavement Performance Database, Transportation Research Board, 2009

Table 2. Long-Term Pavement Performance (LTPP) Resources

Table 3. Estimated Annual Expenditures for Highways and Roads in 2006 Dollars Under SAFETEA-LU¹

¹Safe Accountable Flexible Efficient Transportation Equity Act: A Legacy for Users, Public Law 109-59.

Projected Cost/Benefit Ratios

In 2007, the Congressional Budget Office published a paper documenting "Trends in Public Spending on Transportation and Water Infrastructure, 1956 to 2004." ²¹ This report provides public expenditures (on the Federal, State, and local levels) for both capital spending and operation and maintenance spending, and it also breaks these expenditures down by type of infrastructure, including highways and roads. Annual expenditures under current legislation²² are provided in table 3. Using numbers from the 2007 report as a base and subtracting the amount spent on bridges, one can extrapolate that more than $114 billion is spent each year on roadways and highways. Typically 40 percent of that amount is dedicated to pavement construction and maintenance; thus the annual investment in pavements totals about $45.6 billion.

Quantification of the return on research investments can prove quite challenging. In most instances, the research does not include a discussion of cost implications, and assumptions must be made. This scenario utilizes cost information whenever possible and is very conservative in assessing the benefit. Simply providing a cumulative savings is not realistic since independent findings do not necessarily provide a 1:1 cumulative relationship. For instance, it is not practical to suggest that 10 separate findings, each resulting in "saving" a single half inch in a pavement design, would cumulatively provide 5 inches of savings.

Suppose the return on investment (savings) from the LTPP data since program inception in 1989 is one-quarter of 1 percent (0.0025), or $1.7 billion. As LTPP monitoring is continued past 2009, the annual savings, beginning in 2015, is expected to be about $456 million per year, or about 1 percent of the total pavement investment—double what could be expected if monitoring ended today (table 4). Over a 10-year span (2015 to 2024), the savings achieved as a result of continued monitoring will total $4.56 billion.

Table 4. Projected Savings as LTPP Data Are Utilized

To reiterate, the estimated savings shown are extremely conservative. Considering that the MEPDG team estimates $1 billion in annual savings from implementing the new design procedure, and—as demonstrated herein—that LTPP's benefits range much more broadly than supporting development and implementation of the MEPDG, it could be argued that future LTPP cost savings should start at 10 figures.

By any measure, the LTPP program has already provided a substantial return on investment, with a benefit–cost ratio exceeding 6:1. Put in the context of other large research programs, this number is quite reasonable. For instance, the estimated return on research investment for MnROAD is 8.9:1,23 and Washington DOT has documented returns on its State research funds at over 18:1 when considering all funding sources in the State.24 In fact, the benefit–cost ratio for LTPP over the 2015–2024 period is projected at over 50:1, using recent AASHTO and TRB estimates for proposed levels of funding support. Furthermore, even greater returns can be achieved through expanding future monitoring activities to pavement materials and design methods that have been developed since 1987.

Better estimates of traffic volumes and loads support more
rational allocations of construction and rehabilitation dollars.

FHWA-HRT-10-071