A growing number of highway projects are greening rights-of-way with solar power and other renewable sources of energy.

Significant sections of the Nation’s surface transportation system are at risk due to changes in the Earth’s climate. The effects of climate change, such as more frequent and intense heat waves and flooding, are already causing impacts on the Nation’s transportation infrastructure. State Route 37 near San Francisco Bay, for example, is at risk of flooding due to rising sea levels, according to the California Department of Transportation. In another western example, roads in Fresno, CA, are wearing more quickly due to the increasing duration of heat waves and the high temperatures they produce. On the east coast, catastrophic flash flooding associated with Tropical Storm Irene in 2011 resulted in significant damage to transportation infrastructure: Erosion destroyed roads and rail beds, undermined bridge foundations, and washed out culverts.

Transportation agencies are working to balance vulnerabilities and risks, and to identify strategies to adapt infrastructure to the effects of climate change. To this end, the National Research Council of the National Academies’ Special Report 290: Potential Impacts of Climate Change on U.S. Transportation describes the nature of the potential impacts and suggests appropriate adaptation strategies and organizational responses.

Unfortunately, the costs associated with adaptation strategies strain transportation budgets that are already tight. Funding for the Nation’s surface transportation system has declined over the last decade, and State transportation agencies are increasingly challenged by the shortfall in resources from traditional funding sources, such as from motor fuel and highway use taxes. In Intergovernmental Challenges in Surface Transportation Funding, the Pew Charitable Trusts reported that between 2002 and 2011, surface transportation funding fell by $27 billion, or 12 percent. In addition, both the Highway Account and the Mass Transit Account of the Highway Trust Fund are nearing insolvency. In light of shrinking budgets, transportation agencies are seeking ways to reduce costs and generate revenue.

Reducing greenhouse gases can help mitigate climate change. To help reduce greenhouse gas emissions within the confines of tight budgets, some State transportation agencies are using highway rights-of-way (ROW) to install renewable energy technology, such as wind turbines and solar panels, to generate electricity and supply it to utility companies. Depending on the site, ample highway ROW--including land alongside the highways, in the medians, within interchanges, and beyond the clear zones--can be ideal for such technology if it is consistent with the continued use, operations, maintenance, and safety of the highway facility, and will not impair the highway or interfere with the free and safe flow of traffic.

In addition to the environmental benefits of using clean, renewable sources of electricity, departments of transportation also stand to gain by lowering energy costs and creating new revenue streams. In some cases, the developer or utility installs the technology and then pays rent to the State for use of the land. The DOT also can form agreements with utilities to purchase the electricity generated by the technology at favorable rates over long periods. Those purchases can help offset the costs of purchasing electricity to provide lighting for other segments of the transportation infrastructure.

A New Light for Rights-of-Way

International transportation agencies have long installed renewable energy technologies within highway ROW. Since the 1980s France, Germany, the Netherlands, Switzerland, and the United Kingdom have all installed various types of solar arrays along highways. But the practice has only recently caught hold in the United States. Prior to 1988, the Federal Highway Administration prohibited the installation of utilities within interstate ROW, and many States adopted the same policy for State highways. This prohibition was consistent with the American Association of State Highway and Transportation Officials’ policies for longitudinal accommodation. In 1988, the FHWA policy changed to allow each State to decide whether to permit utilities within interstate ROW and to specify the conditions for approval, or to continue to adhere to the stricter AASHTO policies.

The 1988 FHWA policy also stated that public utilities (that is, utility service available for public use) that were “in the public interest” could be allowed in interstate ROW under a DOT’s approved utility accommodation policy. The conditions are that the utility service needs to be accommodated in ways that are safe for the traveling public and do not interfere with the operation of the highway.

The development of renewable energy technologies and alternative fuel facilities since then, and of opportunities to place these facilities within highway ROW, has caused FHWA and the States to reexamine the existing definition of “utility.” Some States do not view, or have not made a decision about, renewable energy installations as utilities, which is part of the reason why the practice has not been adopted more widely.

In 2008, the Oregon DOT became the first agency in the United States to install a solar panel array along a highway ROW. (See “Spotlight on Solar Arrays” in the November/December 2012 issue of Public Roads.) For its solar highway demonstration project, Oregon DOT installed 594 ground-mounted solar panels at the interchange of I–5 and I–205 in Tualatin, in the southern Portland metropolitan area. The panels produce approximately 130,000 kilowatt-hours of electricity annually--about one-third of the amount needed to illuminate the interchange.

“The project has been highly visible,” says Oregon DOT program manager Allison Hamilton. “We expect approximately 1.6 billion motorists to drive by the panels over the structures’ lifetime.”

Following the success of Oregon’s project, several other State transportation agencies began considering similar projects. The Ohio DOT partnered with the University of Toledo to install a large array of solar panels north of the Veterans’ Glass City Skyway bridge next to I–280 in Toledo, OH. The agency wanted to generate electricity to offset the bridge’s lighting consumption, as well as promote the use of solar energy in the State. The array installation began operation in January 2011. Despite this and a handful of other installations across the country, renewable energy facilities in highway ROW were at that time still considered fairly uncharted territory in the United States.

*Exlcudes renewable energy projects located at highway ROW not directly alongside the roadway, such as at rest areas or carports.

When these initial projects were just getting underway, the regulations that governed the use and management of highway ROW did not address renewable energy facilities, which present special challenges. Depending on the location, statutory or regulatory constraints or environmental, economic, or political variables may limit opportunities for developing renewable resources. For example, a State’s utility rules for net metering--a billing mechanism that credits customers who add electricity to the grid--may limit the amount of energy that a given site can generate. Finding an area that can support renewable energy facilities and is not otherwise being used or designated for future use also can be challenging. For example, long-range transportation plans may present potential siting conflicts, or other incompatibilities could arise such as wind project sites that might interfere with airport activities.

FHWA anticipated that State transportation agencies interested in Oregon DOT’s efforts might have questions about using renewable technologies. Dave Leighow, a realty specialist with FHWA’s Office of Real Estate Services, recalls internal conversations around that time: “We decided to consider the experience of Oregon DOT as an opportunity to take a broader look at the regulatory landscape related to renewable energy and highway ROW.”

In 2009, FHWA issued a memorandum titled “Guidance on Utilization of Highway Right-of-Way,” which clarifies how highway ROW can be used for renewable energy facilities. The guidance details when a State transportation agency can accommodate renewable energy facilities under its approved utility accommodation policy and when it would require an airspace lease (that is, a lease to cover highway air rights, which describe the area above or below the transportation facility and located within its ROW boundaries). Non-highway use of interstate ROW is subject to airspace leasing requirements, which involve charging current fair market value or rent for use of the ROW. This requirement may be waived if the agency shows that an exception is in the overall public interest for social, environmental, or economic purposes. This exception may be appropriate for activities that mitigate climate change or contribute to improvements in air quality.

A year later, FHWA sponsored a research effort to learn more from Oregon DOT and other State transportation agencies contemplating highway renewable energy projects. FHWA published the resulting report, Alternative Uses of Highway Right-of-Way, in January 2012. The report provides information to help State transportation agencies and local public agencies evaluate the feasibility of installing renewable energy technologies in ROW and identify effective practices for doing so. (Editor’s note: The authors of this Public Roads article wrote the report.)

The Trend Continues

At the time that FHWA published Alternative Uses of Highway Right-of-Way, two early adopters--Oregon DOT and Ohio DOT--had built solar energy projects within highway ROW, and the Texas DOT had constructed wind turbines at two rest areas. State transportation agencies in California, Colorado, and Massachusetts were actively developing projects or conducting feasibility studies to identify promising locations to implement a variety of renewable energy technologies. However, no other State transportation agency had pioneered the use of highway ROW for solar energy projects in the way that Oregon DOT was attempting.

In addition to its solar highway demonstration project, Oregon DOT constructed the Baldock Solar Station, a 1.75-megawatt solar array at the French Prairie Rest Area on I–5 in Clackamas County. The 6,994-panel array sits on about 7acres (2.8 hectares) of Oregon DOT property on the east side of the northbound rest area. The Oregon DOT placed the solar power plant into service in January 2012, and it now produces approximately 1.97 million kilowatt-hours of clean, renewable energy annually.

Reflecting on the first years of Oregon DOT’s two solar highway projects, Hamilton believes that the agency has found an approach that works. “Our agency essentially has the basics covered now,” she says. “The initial excitement may have waned a bit, but the projects are working perfectly. They require very little maintenance and basically blend into the background, so to speak. They operate themselves.”

She notes that although the weather obviously affects the panels’ output during the winter months, overall output has exceeded initial estimates. And concepts that were at first largely unfamiliar to the agency, such as retrieving renewable energy tax credits, have now become more routine.

“The challenge I think DOTs may face as they consider highway renewable energy projects,” Hamilton observes, “is finding utility partners willing to take on projects they may find unconventional or too small. The costs are coming down, but they may still be too high for some utilities.”

Beyond Highway Clear Zones

State transportation agencies are considering not only the properties adjacent to highway clear zones for use in generating renewable energy, but also all of the ROW. At least seven State transportation agencies have constructed solar array or wind turbine installations at rest areas or carports flanking highways. Some agencies are also considering brownfields as sites for generating renewable energy. The U.S. Environmental Protection Agency has developed a Liability Reference Guide for Siting Renewable Energy on Contaminated Properties for stakeholders considering such projects.

The Oregon DOT developed its solar highway demonstration project through a partnership with Portland General Electric, which owns and operates the plant, and U.S. Bank as the utility’s tax equity partner. The partnership makes use of State and Federal renewable energy tax credits and grants offered through Energy Trust of Oregon and the utility’s Clean Wind Fund.

Solar energy produced by the array feeds into the grid during the day, in effect running the meter backwards for energy needed at night to light the interchange through a solar power purchase agreement with the utility. The success of the demonstration project led Oregon DOT and Portland General Electric to collaborate to build the larger Baldock Solar Station. Portland General Electric operates and maintains the Baldock array under a lease arrangement with Bank of America, which financed and owns the project. The return on these investments includes generating renewable, clean energy that goes into Portland General Electric’s grid to serve its customers; creating new sustainable businesses and jobs; demonstrating innovative green technology; offering national leadership in sustainable development; and providing the State with an opportunity to gain revenue.

In the 3 years since FHWA published Alternative Uses of Highway Right-of-Way, State transportation industries have maintained their interest in solar electricity facilities within ROW. In addition to Oregon and Ohio, Colorado and Massachusetts have installed solar arrays along ROW. Texas and Florida have conducted research studies and geospatial analyses to assess highway renewable energy project options, and other States have issued requests for proposals or information regarding the development of solar panel installations along highway ROW.

An Exemplary Program

Massachusetts has demonstrated significant commitment to the installation of renewable energy technology along its roadways. The Massachusetts Department of Transportation (MassDOT) has installed solar arrays along six rights-of-way since October 2012, and has several other projects planned.

“These solar generation facilities will showcase MassDOT’s commitment to sustainability and innovation,” says MassDOT renewable energy specialist Hongyan Oliver.

In 2013, the agency initiated a statewide Solar Photovoltaic Energy Program to build enough ground-mounted solar photovoltaic facilities to generate up to 6 megawatts of power at multiple properties owned by the Commonwealth and located within the ROW. As MassDOT developed the program, the agency coordinated with the FHWA Massachusetts division to update its utility accommodation policy to include guidelines for renewable energy technologies installed on MassDOT real property or along its highways. The policy now outlines safety criteria and design standards, the project development process, compensation requirements, and license and lease agreements relevant to renewable energy projects on highways. The policy is available online at www.massdot.state.ma.us/Portals/8/docs/utilities/UAP.pdf.

To implement the program, MassDOT worked with a consultant to screen potential sites for their solar generation potential, considering shading, topography, existing drainage, ground utilities, proximity to electricity transmission lines, environmental concerns, any conflicting use, and visibility. Of more than 600 possible locations, surveyors identified 14 promising sites for ground-mounted solar panel systems. MassDOT’s highway administrator ultimately endorsed 10 parcels at 8 locations for initial project development. Several of the parcels encompass acreage at interchanges and medians of I–90, which runs east-west. MassDOT is currently analyzing other State highway locations as potential sites in pursuit of its goal to reach or surpass 6 megawatts of power generation.

Partnering to Finance Renewable Energy Projects

Transportation agencies facing limited budgets may not have resources readily available to fund the installation of renewable energy facilities on their highway lands. Commonly, DOTs that have implemented highway renewable energy projects successfully have relied on public-private partnerships. Under one business model, for example, the State transportation agency would not provide any upfront capital for the project. Instead, it would partner with a utility or private developer that would finance, construct, maintain, and decommission the renewable energy facility. The developer would recover its investment over time by selling the electricity generated by the facility and by taking advantage of Federal and State tax incentives, if applicable.

The recent projects in Massachusetts offer an example of this business model. MassDOT selected a developer to design, construct, finance, operate, maintain, and decommission its solar facilities. Under this arrangement, all partners stand to benefit financially. The utility will have some of its demand for power offset by the new generating source. The developer will receive all of the projects’ State solar renewable energy credits and tax incentives. And MassDOT, which did not use any State funding for capital costs on the projects, will purchase 100 percent of the electricity generated through a 20-year rate schedule that is significantly lower than the utility rates that MassDOT typically pays.

In addition, MassDOT will receive annual rent payments from the developer, which is leasing the land where the solar arrays are installed. MassDOT also benefits from the State’s existing net metering policy, which allows host customers to obtain net metering credits for exporting any excess power generated from qualified distributed generation units back to the grid. Between the reduced electricity costs and the lease revenue, MassDOT stands to gain from its solar energy program. MassDOT has the option to either extend the contract or purchase the facilities at fair market value at the end of the 20-year initial contract period.

The Conversation Builds

State transportation agencies, renewable energy developers, utilities, and other stakeholders continue to express interest in evaluating highway ROW for innovative, sustainable uses. Some are viewing these projects as more than simply one-off projects, and rather as a common way of doing business. As such, some State transportation agencies are paying close attention to regulatory, industry, and stakeholder developments in the renewable energy industry. Governmental policy changes could make highway ROW even more appealing for renewable energy development.

The ongoing awareness and appeal of these projects has helped motivate dialogue about the future. For example, the Transportation Research Board’s Committee for Waste Management and Resource Efficiency recently established a new subcommittee on infrastructure, facilities, and rights-of-way as sustainable resources to share knowledge and research on the alternative and innovative use of transportation assets to support overall environmental and economic sustainability objectives.

Beyond Solar Panels

In addition to using solar panels to convert sunlight into electricity, some State transportation agencies are piloting or considering other sources of renewable energy for highway ROW, including wind, organic materials, and geothermal sources. Texas and Missouri DOTs have installed wind turbines near highways. Transportation agencies in Michigan, North Carolina, and Utah have partnered with the Freeways to Fuel National Alliance to explore the use of highway ROW for growing crops that can be processed into biofuels. Others have used geothermal technologies to help warm bridge decks or power rest areas. Applications involving hydrokinetic technologies (for example, harvesting energy from waves and tides to power turbines) may present viable options in the future.

There is ample reason to explore the subject further, as demonstrated by the pioneering transportation agencies that have installed renewable energy technologies in highway ROW. These projects can provide a way for State DOTs to offset their carbon footprints, meet sustainability goals, and help create or sustain a local, green job market. They can also help reduce highway maintenance and operational costs while potentially generating additional revenue for transportation agencies.

Although the collective experience with such projects is growing, State DOTs continue to face considerable economic, ecological, legal, and political challenges in developing and implementing renewable energy projects in the highway ROW. FHWA supports State DOTs’ pursuit of these projects, and is a resource for information on issues that may arise and topics that States need to consider when designing, developing, and implementing renewable energy projects in the highway ROW.

Gina Filosa is an operations research analyst at the Volpe Center. She holds an M.A. in urban and environmental policy and planning from Tufts University and a B.A. in environmental studies from Providence College.

Carson Poe is a transportation industry analyst at the Volpe Center. He holds an M.A. in energy and environmental analysis from Boston University and a B.A. in interdisciplinary studies, environmental policy and planning, from Appalachian State University.

For more information, see www.fhwa.dot.gov/real_estate/right-of-way/corridor_management/alternative_uses.cfm or contact Gina Filosa at 617–494–3452 or gina.filosa@dot.gov, or Carson Poe at 617–640–8314 or carson.poe@dot.gov.