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Version 1.3

How Does INVEST Measure Sustainability?

INVEST is based on a collection of sustainability best practices called "criteria." Each criterion describes a best practice and assigns it a point value based on its sustainability impact.

Each INVEST criterion describes a particular sustainability best practice and assigns it a point value (or "weight") according to its relative impact on transportation sustainability. The points associated with the criteria that are achieved for a given program or project are added together to give a total score. That score can then be used internally for purposes such as tracking progress toward more sustainable infrastructure, tracking integration of sustainable best practices into projects, and stakeholder and community outreach.

The fundamental basis for weighting the criteria is based on both the triple bottom line principles and related benefits of sustainability (see How Are the Criteria Weighted?).

Version 1.3 of INVEST applies weighting for the Project Development (PD) criteria only. Criteria in the System Planning modules (SPS and SPR) and the Operations and Maintenance (OM) module are all equally weighted at 15 points (except the bonus criterion in each SPS and SPR which is valued at 10 points).

Principles of Sustainable Highways

A sustainable highway should be planned or replaced, financed, designed, constructed, inspected, operated and maintained in a way that provides sustainable benefits related to the three principles of the triple bottom line: Social, Environmental, and Economic. These principles can be metrics for evaluation, with a focus on both natural laws and human values. Natural Laws encompass the essential understanding that humans live and operate within the context of ecosystems with finite resources (the Environmental principle). Human values cover both the Social and Economic principles. The Social principle can be broadly understood as seeking quality of life for all; that is, the ultimate satisfaction of basic human needs. The Economic principle can be defined in terms of the efficient or productive use of public capital, including the need to avoid deterioration of capital assets.

Highway project development (including project planning, design, and construction) should seek to apply these principles. These principles are useful because they begin to define specific results that can be achieved by improving highway sustainability. They begin to provide distinct reasons for highway project development to incorporate such diverse concepts as climate change, environmental protection, judicious use of funds, regional air quality improvement, construction quality incentives, recycling promotion, social equity, and environmental management system use. If done effectively, the result should be more sustainable highways.

Relating Criteria to Principles

Each criterion in INVEST contributes to sustainability by benefitting the different combinations of the triple bottom line principles: Social, Environmental and Economic. This graphic is used throughout the tool to indicate the primary and secondary triple bottom line principles supported by each criterion. Colored rings indicate supported principles and a section of the criteria write-ups called “Sustainability Linkage” further describes the impacts considered. Emphasis is on the primary and secondary benefits although often, there are tertiary benefits that are not discussed that may support a principle or principles not indicated.

This "mapping" of criteria to sustainability principles is important because it provides the basis by which a criterion can be considered to contribute to sustainability. Criteria mapping may involve some subjective judgment; but, where practical, mapping an item back to sustainability is done using empirical evidence. The goal is to create an evaluation system where each criterion is, to the extent possible, shown through existing research to have an impact on sustainability.

Mapping criteria to triple bottom line principles can assist users in selecting criteria to pursue based on the type of project or desired sustainability goals and objectives. Importantly, the nature of sustainability requires users to make trade‐offs between or among different aspects of sustainability. For instance, one might have to select between using recycled material that must be trucked over a long distance or using locally provided virgin material. Both options (recycled material vs. local material) relate to sustainability (e.g., Environmental and Economic principles). Decisions regarding these types of trade‐offs are likely to be at least partly based on the specific project and the interests of its owners and stakeholders. INVEST allows users to choose from a long list of criteria to fit the specific project or goals. The following tables provide a consolidated mapping of affected triple bottom line principles for criteria included in each of the INVEST modules.


Next > How are the Criteria Organized?


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