One of the many challenges facing federal state and local transportation agencies developing sustainable "green highway systems" is the lack of research and the subsequent adoption as inclusions in design/contractor specifications. If new sustainability based actions are to be realized on highways, new approaches and technologies need to be tested, proven and adopted by DOTs. A menu of sustainability based specifications needs to be provided to transportation designers, contractors and operation/maintenance professionals to improve implementation timing.
Why does it take so long for new and innovative sustainable ideas to become adopted by state and local departments of transportation (DOTs)? Maybe I am missing something, but it appears that many DOTs do not directly and quickly adopt research and new sustainability based specifications developed and approved by other states DOTs, agencies or professional associations. I also appears that other countries, especially in Europe, are more progressive and proactive in adopting and implementing sustainability-based technologies for transportation.
The Federal Highway Administration's (FHWA) Every Day Counts (EDC) is designed to identify and deploy innovation aimed at shortening project delivery, enhancing the safety of roadways, and protecting the environment. These goals are worth pursuing for their own sake. But in challenging times, it's imperative to pursue better, faster, and smarter ways of doing business. EDC is designed to focus on a finite set of technical initiatives. The FHWA EDC program is currently promoting five current innovation technologies to state and local partners (1):
- Adaptive Signal Control
- Geosynthetic Reinforced Soil Integrated Bridge System
- Prefabricated Bridge
- Safety Edge
- Warm-Mix Asphalt
I think it is great that FHWA Teams will work with our state, local, and industry customers to deploy the new initiatives and will develop performance measures to gauge their success; however, the innovation technologies need to be expanded beyond these very limited five technologies. EDC actions need to be expanded and be more sustainability-based towards environmental enhancement, efficient energy management, water conservation and material reuse-recycling. As part of the EDC effort, FHWA needs to actively promote the creation of proven sustainable-innovative technologies into specifications; this will aid in implementing innovative technologies is a more expedited fashion. These expedited actions will support the reduction of greenhouse gas emissions and reduce material and energy costs.
On a side note, it is hoped that the Department of Transportation/FHWA will consider better performance on meeting the sustainability targets established by President Obama's Executive Order 13514; Department of Transportation /FHWA performed marginal to poor in the categories of: 1) use of renewable energy, 2) reduction in potable water intensity, 3) reduction in fleet petroleum use, 4) green buildings, and 5) scope 3 greenhouse gas emissions reductions (2). Improved sustainability performance at an agency level will provide more creditability to Department of Transportation/FHWA when promoting new innovative technologies and their commitment towards sustainability.
The following are eleven of many innovative and sustainable ideas and technologies that I found by performing a recent literature search. These are some innovative technologies that should be actively considered, tested, promoted and implemented by FHWA and state DOTs; many of these practices are currently being used in Europe.
I hope my readers find these brief summaries interesting and informative:
1. Pressure Plate Piezoelectricity
The charge that gathers in crystal and ceramic solid materials in response to strain has recently begun to gain the interest of entrepreneurs and scientists alike. A number of materials are piezoelectric, including topaz, quartz, cane sugar, and tourmaline; meaning an electrical charge begins accumulating inside these materials when pressure is applied. A company called Innowattech is installing strips of asphalt embedded with piezoelectric materials. According to the company, the generators could produce 1 MWh of electricity from a four lane highway, or enough to power 2,500 homes. Princeton University researchers combined silicone and nanoribbons of lead zirconate titanate to create PZT, an ultra-efficient piezoelectric material that can convert up to 80 percent of mechanical energy into electricity (9).
2. Solar Roadways
In Idaho, a 45 mile section of a highway is currently being tested with solar panels installed onto the road surface. Solar roadways may efficiently generate power because they allow for generally unobstructed sunlight to strike the surface. Theoretically, the roadways in the U.S. can supply the land area required for the country to replace other energy sources with clean, renewable solar power. Solar Roadways is an Idaho-based company started by an electrical engineer, Scott Brusaw, after he found out that covering just 1.7% of the country's land surface in the Continental United States with PV panels, could power the country's entire energy demands with solar power.
The innovative solar roadway concept includes the installation of a durable glass-based roadway surface in which photovoltaic panels will be wired directly into the grid. Solar roadways would also be heated during the winter by the system, melting ice and snow and increasing safety for drivers. The top road surface layer contains the solar collector cells, LED lights, and heating element, and is covered with a translucent, high‐strength glass that still provides traction for cars. The electronics layer is in the middle, and contains a microprocessor board that can sense vehicle and pedestrian loads, control the heating element for snow and ice removal, control variable lighting, and provide communications (6,8).
3. Road Energy Systems (RES) Thermal Energy Asphalt Pavements
Asphalt pavements have gained acceptance in recent years as an interesting new renewable energy source. As asphalt pavements can heat up to 70 degrees Celsius during solar irradiation, a comparison with solar hot water systems seems obvious. Several designs have been developed to extract heat from an asphalt pavement. Most available solutions apply a heat exchanger design by incorporating tubes in the asphalt pavement. In addition to its energy potential, the advantage in using an asphalt collector is the maintenance of the pavement. In summer time the maximum temperature of the asphalt pavement can be reduced so that the chance of permanent deformation is mitigated. In winter time, it is possible to avoid slippery roads by increasing the minimum pavement temperature. Snow-free pavement is the result, requiring no salt or other environmentally hazardous contaminants. RES® has been successfully applied in several road and airport projects in the Netherlands, Belgium and Scotland and there is a growing interest and demand for the technology in the US and China (3).
4. Heated Bridge Decks
Heated bridge decks in colder climates can be beneficial for a number of reasons: 1) the life cycle of bridges improves when bridges are temperature controlled (cooled in the summer, and heated in the winter); the amount of expansion and contraction stresses is reduced. This can extend the life of a bridge by reducing the cyclical wear and tear on joints and panels, 2) heated decks can increase safety and improve mobility, heated bridges can melt black ice and light snow accumulation. By removing these potential hazards, there could be fewer accidents on bridges. With fewer accidents, bridges would be passable during inclement weather, and traffic congestion (idling, vehicle emissions) could be reduced, 3) reduced infrastructure deterioration is realized by the reduced use of salt. The salt often corrodes steel and shortens the bridge lift. Also, salt is only effective within certain temperature ranges. If bridge decks were internally heated, the use of salt could be reduced dramatically, 4) improvement of the surrounding environment could be seen by using less salt or sand to de‐ice bridge decks which could potentially improve the surrounding groundwater and benefit local flora and fauna, 5) reduced required maintenance during snow events by making snow removal easier because the heated deck surface could prevent hard ice from forming. Snow plows could potentially become more efficient by removing snow faster (and with fewer vehicle emissions).
Three methods for heating bridges are hydronic, heat pipe, and electrical. Hydronic involves circulating a heated fluid through pipes that are embedded within the bridge, near the surface of the pavement. Fluid can be heated by various sources including geothermal energy. Renewable energy sources such as wind or solar power can also be developed to run the heating unit. The cooled fluid is pumped back to the source and reheated to circulate again. Heat pipe, a series of pipes containing a 'working' fluid, is embedded in the bridge deck. The fluid is vaporized at one end of the pipes, and condenses (releasing heat) as it travels to the other end. Through capillary action or gravity, the condensed fluid returns to the heat source to be vaporized again. The electrical method involves electrical current pushed through metals embedded in a concrete bridge deck. This current produces heat, which is then transferred to the surrounding materials. Heating cables placed within the concrete can also be used. Heated bridges are mainly meant to eliminate black ice and light snow, they are not designed for or intended to combat or melt heavy snowfall. Application of heated bridge technologies generally can be justified economically and practically only for installations in a temperate region (5).
5. Greener Roads Through New Mixing and Compaction Technologies
The Ammann Compaction Expert (ACE) enables the operator of a roller to choose a vibration mode on the road construction site. Very fast compaction is achieved and the current level of compaction is measured constantly. Excessive or over-compaction is prevented and in addition, the energy consumption of the machine itself is minimized. Intelligent compaction with high-tech measurement and control equipment therefore is a key enabling technology for the wider application of low-temperature asphalt. Lowering the maximum temperature of the asphalt during production and mixing allows a reduction of fuel consumption at the mixing plants, since less energy is needed to heat the minerals and the bitumen. The second advantage of lower temperatures is the significant decrease of construction worker exposure to asphalt smoke and fumes (3).
6. Environmentally Sound Road Marking Products
Ostrea Route and Ostrea Spray are road marking products made from pine resins, vegetable oils and ground oyster shells. The environmental/health balance sheet for the water-based road paint show impacts at least 30% lower than for a typical solvent-based paint. Atmospheric VOC emissions are an impressive 88% lower, especially during the application phase. An airless line marker shows several clear advantages, compared to other machines/systems: superior operator ergonomics and safety; excellent application quality; centralized control station management of the main marking work; optimum reliability, safety and service life; lower noise levels. The two marking products replace the use of quarry lime thus eliminating the need for extraction and much of the raw material transport. They reduce the use of non-renewable petroleum resources and reduce greenhouse gas emissions by 20% on application and over the whole product life cycle and eliminate packaging waste (3).
7. Terminal Blend Tire Rubber Asphalt (TBTRA)
TBTRA creates quieter and safer driving conditions and also provide a very durable surface while creating a more environmentally friendly atmosphere. After extensive research, it was learned that using "wet" and "dry" tire rubber asphalt manufacturing processes led to excessive smoke and aroma being released into the atmosphere at asphalt plants. However, using a terminally blended manufacturing process proved to be the most environmentally-friendly option. TBTRA is produced in a closed-system plant, preventing smoke and particulates from entering the atmosphere. In addition to being smoother, quieter, and safer-particularly during rainstorms, the TBTRA has proven to have a significantly lower concentration of roadway pollutants running into the roadside ditches compared to contaminated stormwater runoff of other asphalt pavement (3,7).
8. Biofuels Based Pavements
Biofuel has several applications as an alternative to petroleum-based asphalt. A biofuel co-product (BCP) containing lignin can be used as an agent to stabilize pavement bases and sub-grades in road construction. The Iowa DOT and Iowa State University released a report in April, 2010, which showed that BCP is a viable material for soil stabilization. The BCPs tested demonstrated excellent potential for stabilizing low-quality soils for low and high volume roads. Another innovation that is being studied at Iowa State University is referred to as "Bioasphalt." Bioasphalt is made using a 5% mixture of bio-oil as a potential alternative to petroleum-based products. Bioasphalt utilizes renewable materials and can be mixed at a lower temperature, which saves energy and reduces fossil fuel emissions during the mixing process. Bioasphalt is currently being tested on a bike trail in Des Moines, Iowa. If the tests are successful, further demonstrations will be conducted containing higher percentages of bio-oil (6).
9. Photocatalytic Concrete
Self‐cleaning, photocatalytic concrete contains a type of cement mix coated with highly reactive titanium dioxide particles which react to break down harmful air pollutants. When exposed to sunlight, the concrete's titanium dioxide compound (known as TX Active) has its electrons combine with pollutants, such as formaldehyde, benzene, and ammonia, to break down into innocuous water molecules. This process cleans the concrete by deflecting and degrading dirty air particles. In addition to cleaning the air, titanium dioxide helps keep the concrete cool by reflecting sunlight. Self‐cleaning concrete has been actively researched over the past ten years by the world's fifth largest cement producer, Italcementi. Photocatalytic concrete has been experimented with success throughout the world. In Italy, a busy Milan street saw its nitrous oxide emissions reduced by 60% after being paved with photocatalytic concrete. A project that paved roughly two acres of an industrial area in Bergamo, Italy with photocatalytic concrete caused nitrous oxide emissions to reduce by 45%. Experts claim that if 15% of exposed urban surfaces were coated with TX Active then air pollution could be diminished by as much as 50%. Photocatalytic concrete is also economical because the TX Active only needs to be applied to the exposed surface rather than throughout an entire substance (6).
10. Design for Deconstruction
Designing for deconstruction (also referred to as designing for disassembly) involves managing and extending the life-cycle of building and construction materials. In terms of transportation, highway construction projects could take advantage of reuse or recycled building materials (such as lumber for formwork) from another worksite instead of consuming raw, new materials. This reduces the impact on the environment and can be more cost-effective than purchasing new materials. Also, by minimizing the amount of and types of material used in construction, fewer items are left to recycle or reuse at the end of the structures life cycle. When demolishing or removing a roadway structure, the concept of designing for deconstruction encourages careful removal of construction components and materials, so they can be purposefully reused elsewhere. This practice not only increases the life cycle of materials, but also reduces the amount of waste or rubble that traditionally needs to be sent to a landfill (6).
11. Solar, Wind Power Generator Jersey Barriers
Researchers in the United States are seeing Jersey barriers as a source for wind and solar energy. Mark Oberholzer, a Houston based architect and former professor at Rice University, is developing a concept to harness the energy produced by wind from passing traffic along a highway. He is researching the design of Jersey Barriers embedded with miniature wind turbines to capture wind generated from passing vehicles. Initially, a single row of vertical axis turbines was to be installed but the design has been revised to embed a dual row of turbines. While the energy can be redistributed to the electrical grid, feeding it to an adjacent electric railway would minimize the losses and inefficiencies associated with moving electricity long distances. The researchers claim that the generated solar energy can be used to supply power to the highway's night-time illumination (6).
(1) FHWA Every Day Counts; http://www.fhwa.dot.gov/everydaycounts/index.cfm
(2) Executive Office of the President Council on Environmental Quality; http://www.whitehouse.gov/administration/eop/ceq/Press_Releases/April_19_2011
(3) International Road Federation Innovative Practices for Greener Roads (2009);
(4) Building Green Infrastructure International Road Federation; http://www.springsgov.com/units/communications/Building_Green_Infrastructures.pdf
(5) An Electronic Freeway to the Future; http://chusid.com/pdf/CI-We-May2011.pdf
(6) Sustainable Transportation Solutions and Emerging Technologies (June 2011) I-15 Mobility Alliance; http://www.i15alliance.org/pdfs/tech_memos/sustainability_emerging_technologies/I-15CSMP_Sustainability_FINAL.pdf
(7) Building Green Infrastructures; http://www.springsgov.com/units/communications/Building_Green_Infrastructures.pdf
(8) Solar Roadways; http://www.solarroadways.com/main.html
(9) Electricity Generating Dance Floors and Other Miracles of Piezoelectricity; http://www.good.is/post/electricty-generating-dance-floors-and-other-miracles-of-piezoelectricity.