Sustainability is a difficult thing to measure and communicate. Perhaps because of this, a variety of different infrastructure markets have become involved with sustainability rating systems. There are a number of these systems relevant to the asphalt pavement industry. Although building rating systems, such as LEED (Leadership in Energy and Environmental Design) are well-established, others designed for general infrastructure or roads have gained a following in the last five years. By most measures, the influence of these road-related rating systems is growing in the transportation infrastructure community, and we can expect their use to grow in the next decade.
Because these rating systems can be used to evaluate projects within which asphalt pavements are typically included, it is useful to examine how they address the asphalt pavement industry and its products. Broadly speaking, sustainability rating systems for buildings, like LEED, have relatively few points available for asphalt pavements, which is to be expected because they are focused on buildings. However, because asphalt pavements constitute about 70 percent of all highway and street construction put in place annually in the U.S., one might expect infrastructure systems, and especially road-related systems, to address these pavements more thoroughly.
It is important that you understand what is in a particular rating system. Each rating system is unique and offers road owners and agencies specs they can use to ensure greater sustainability, while offering contractors capable of meeting these rating systems greater competitive advantage.
What counts and what doesn’t
Recently, Manisa Veeravigrom, Ph.D., developed a framework for roadway sustainability rating systems during work on her doctoral studies at the University of Washington by examining 11 existing systems (all the road-related systems available with sufficient documentation) to see what they contained. Among the pavement-related systems, she found that there are some commonly addressed topics:
- construction waste management,
- materials reuse and recycling,
- minimize materials,
- local materials,
- reduce non-renewable energy use, and
- reduce greenhouse gas emissions.
She also found a number of topics that were only addressed in a few systems, if any:
- work site safety,
- job training,
- prevailing wages,
- materials production emissions,
- durable structures (i.e., long-life pavements),
- construction quality control,
- life cycle assessment,
- local employment, and
- cost-benefit analysis (including life cycle cost analysis).
The fact that so few rating systems address these topics is concerning because the asphalt industry, for good reason, also values safety (Safety Innovation Award), training (Diamond Paving Commendation), wages, long-life pavements (APA’s Perpetual Pavement Award), construction quality (e.g., Sheldon G. Hayes, Ray Brown, Larry H. Lemon, and QIC awards), and cost. However, some rating systems do recognize these topics.
How prominent systems stack up
It is helpful to look at a few prominent rating systems in detail to see how they specifically address asphalt pavements. In this section, the LEED version 4 BD+C NC (Building Design and Construction for New Construction buildings), Greenroads version 2, the FHWA’s INVEST version 1.2, and Envision version 2.0 are examined in more detail. Each rating system was reviewed for credits that are considered “pavement-related credits.” This means credits that:
- Can be satisfied or partially satisfied by a paving contractor. These involve actions either specific to paving contractors or generally applicable to any contractor. Sometimes the paving contractor is only one of several entities that need to meet credit requirements in order to achieve points. These are generally items accomplished during construction or credentials possessed by the paving contractor.
- Address asphalt pavements in part or in whole. These generally involve a materials choice (e.g., porous asphalt); materials composition (e.g., recycled content), source (e.g., locally sourced), and manufacturing methods (e.g., warm-mix asphalt); and design (e.g., long life).
Scoring and certification process
While Table 1 shows what is available for pavements, what pavements actually earn through a certification process may be different. Access to detailed data from the first 22 Greenroads-certified projects allows a quick look at this, at least for Greenroads. While all 22 of these projects were certified with the earlier Greenroads version 1.5, in terms of pavement-related points, this version is quite similar to the current version 2 (version 1.5 has 53 of 108 points available for pavements, or 49 percent). For these 22 projects, the following ranges were observed:
- Total points earned: 32 to 46 (average of 37.7)
- Pavement scores: 8 to 23 (average of 15.5)
- Fraction of earned points from pavements: 20 to 53 percent (average of 41 percent).
This indicates that pavement-related credits are achieved at about the same fraction as they are included in the system, although achievement rates can vary significantly between projects.
Working with sustainability rating systems
Given that sustainability rating systems are likely here to stay, an intelligent approach to working with them is warranted. Here are four basic recommendations:
- Understand each significant rating system. First, not all sustainability rating systems are or will ever be used. Many are research efforts that will likely go no further. A few are being actively used to certify projects — most notably LEED, Greenroads, and Envision. The FHWA’s INVEST is only intended to be used as a self-assessment, so it is not used in any certification process. Second, it is worthwhile to understand how each system addresses asphalt pavements. This article is a start, but there is more detail available in reading through the rating system or talking with its director. It is generally not sufficient to read just the credit titles.
- Endorse and use rating systems that best represent asphalt pavements. There are differences between rating systems. Those that best represent asphalt pavements can be useful marketing tools by (1) advertising the sustainable attributes of the asphalt pavement industry, (2) independently verifying the value of these attributes (if the system allows for certification), and (3) understanding what projects pursuing certification are going to want from their asphalt pavement.
- Use your knowledge of sustainability rating systems for competitive advantage. It can be advantageous to align your company with a recognized sustainability brand — especially one that is wholly independent of the industry. In general, a membership fee (these can vary greatly) gets you in the door. Ultimately, there are few recognized sustainability credentials in the industry. A record of working on certified projects, an active membership, and accredited professionals (pass a test on the rating system, become accredited) in your company are the best credentials.
- Use rating systems to expand specifications. Often, specifications will not allow you to do what you know is possible and more sustainable. Sometimes, pursuing certification on a project can provide leverage for changing a specification.
During the last five years, infrastructure and road-specific systems have made good progress: a few are now used to review and certify projects. While asphalt pavements have relatively little influence in building rating systems like LEED, they have comparatively more in infrastructure and roadway rating systems like Greenroads, INVEST, and Envision. Even within these systems, there is great variety in how asphalt pavements are addressed. In general, materials, waste, energy use, and greenhouse gas emissions are usually addressed in roadway rating systems, but jobs, long-life pavement, life cycle cost, and life cycle assessment may not be included.
The LEED v4 BD+C New Construction rating system does not give much significance to asphalt pavements. Greenroads, INVEST, and Envision give more prominence to pavements, but substantial differences exist. A look at Greenroads-certified projects shows that pavement-related credits are achieved at a rate commensurate with their inclusion in the system (an average of 41 percent of all points earned come from pavement-related credits).
There are several ways to work with sustainability rating systems. Understanding what is in the rating systems is important. Once understood, these rating systems can be used as tools that, of course, encourage sustainable practices, but also tools that can provide competitive advantage and expand specifications.
- Veeravigrom, M., 2015, An International Framework for Sustainable Roadway Rating Systems, Ph.D. dissertation, University of Washington, Seattle.
Stephen Muench, Ph.D., P.E., is an associate professor at the University of Washington and a founder and president of the Greenroads Foundation (greenroads.org). This article is reprinted with permission from the January-February 2016 issue of Asphalt Pavement magazine, published by the National Asphalt Pavement Association (asphaltpavement.org).