Building a better mousetrap
by Byron N. Lord
The highway community has a long way to go in nurturing and accepting new innovations and technologies. And, once an innovation is identified, a more robust and systematic program for delivering it and ensuring that it is adopted are necessary steps. What would encourage and facilitate the development of innovations and accelerate their deployment as solutions on the U.S. highway infrastructure?
As noted elsewhere in this issue of PUBLIC ROADS, the Nation's highways are the backbone of the best transportation system in the world, yet more than 17,700 kilometers (11,000 miles) of pavement on the national highway system are in poor condition, nearly 24,000 of its interstate bridges are classified as deficient, and roadway conditions were cited as a factor in approximately 30 percent of the 42,815 highway fatalities in 2002. Many U.S. highways and bridges have far exceeded their original design lives, and demands on them continue to grow.
Even if all the money needed were available to upgrade the system and bring it up to prime condition, would the problem be solved? Actually, if the transportation community used current approaches to building highways, a massive reconstruction program might bring as many problems, if not more, than it would solve. Look at recent statistics: In 2002, nearly 1,200 people died on U.S. highways in construction work zones. In 2001, congestion in highway work zones resulted in 2.6 hours of delay per driver, and 3.1 billion vehicles of capacity loss. And those statistics are at the current construction levels. To gear up for a huge reconstruction program to overhaul the entire highway system, those numbers might logically increase severalfold each year.
"When faced with the magnitude of the challenge and the demand for additional resources just to stem the tide of deterioration and to reduce the delay and disruption," says Gary Hoffmann, deputy secretary for highway administration, Pennsylvania Department of Transportation (DOT), "it becomes obvious that the technology and the practices that built America's highways in the 20th century are no longer adequate for the challenges and needs we face for the 21st century."
But what if the transportation community stepped back and decided to find a better way, a better overall business model? The model would be based on, first, determining the customer needs, then under-taking a global search of other nations and other industries for potential "better mousetraps," or solutions. Upon discovery of a better mousetrap, the industry would need a highly efficient system for adopting and spreading that new technology throughout the highway community. In addition to putting the user first, the transportation community would bring the best solutions into day-to-day practice as a norm rather than as a case-by-case special exception to meet an emergency.
Using this business model would employ new ways to improve drivability, visibility, and traction--to keep drivers in their vehicles and on the roadway--safely on their way to work, home, or play. New techniques would accelerate the construction process, reducing and minimizing the time that lanes are out of service and capacity decreased due to construction. New and better processes, equipment, and materials would be used to manage construction logistics and worksite traffic flow to eliminate or minimize disruption and delay. All of these innovative approaches and technologies then would be made available using a comprehensive technology transfer program.
But the next question, after that long "what if," is "how"? How do agencies obtain all these new approaches and technologies? How will the technologies be distributed? And where does the industry get this new business model?
To bring about this change, the industry must develop an extensive commitment to facilitating the advance of innovation, to look at how things are done in other areas, both inside the highway community and in other fields, both in this country and overseas. Such a program would focus on working with others to:
* Stimulate investment in innovation and accelerate deployment
* Develop an improved technology infrastructure to support highway safety, construction, and quality
* Offer the opportunity and support to bring innovation to the highway community, assisting in refinement and adoption
* Develop improved tools to facilitate achievement of performance standards
* Provide opportunities for a broader segment of the highway construction industry beyond those firms directly involved in the construction of projects
* Sustain momentum
Scope
The types of innovations that might be pursued could include, but by no means are limited to:
* Application of industrial engineering principles to improve the efficiency of highway construction practices
* Integration of automated sensors into construction equipment or highway structures (pavements and bridges) to achieve enhanced real-time process control
* Application of technologies that have proven successful in other industries, other countries, or the U.S. highway construction industry
The Approach
Three key elements need to be developed for this model to work: First, customer needs should define the ultimate outcomes. Without a clear focus, the potential is great for pursuing innovations that really do not fill any need. This process should be a continuous one, so that there is ongoing feedback on the current state of the highway system and the needs of its users.
At the same time, a major database needs to be established to catalog innovations other nations and industries are using that could have an application in America's highway program. Development of this database, too, should be ongoing, so that new innovations are incorporated periodically.
Finally a process should be established to identify adoptions and technical support needs. This process would evaluate needs and capabilities and determine how best to facilitate putting the technology forward as a best practice and to accelerate its adoption into normal practice.
Transferring the Technology
Once innovations are identified--whether through seeing them used by other highway agencies inside and outside the United States or through making a highway application of nonhighway technology--the major challenge will be to get the innovations out to the marketplace: the highway community. This technology transfer will require demonstrations, formal training programs, workshops, and strategic marketing plans for individual innovations.
Again, though, the key to the success of the new business plan is its being embraced by the entire highway community. Merely having the Federal Highway Administration (FHWA) set up some systems without the active participation of the rest of the community would virtually guarantee failure.
Innovations adopted could be included in a toolbox of approaches that highway agencies could turn to. Technology transfer tools and materials, including the development of training, could be promoted to accelerate the adoption of innovations fostered under the technology partnerships.
This effort could establish new business models to meet and keep pace with the needs of the future. Investing in capturing untapped genius and putting it to work to build and strengthen the safety, efficiency, and quality of our Nation's highways follows the examples of so many other areas, from agriculture to communications to military applications.
A few examples of innovations can illustrate the potential for deploying better solutions through technology partnerships. Each of the examples represents innovations that were not previously being practiced in the United States but benefited from design and construction guidance and technical refinements to adapt them to U.S. practice. Today, the United States is enjoying the benefits of these innovations through safer, faster construction and improved quality.
Stone Matrix Asphalt
Stone matrix asphalt (SMA), used in Europe for approximately 30 years, was first developed to provide resistance to abrasion caused by studded tires. In the 1970s, Germany banned studded tires, so the use of SMA mixtures declined because there no longer appeared to be a critical need for these mixtures and because of higher material and construction costs. In the Germany of the 1980s, however, rutting of hot-mix asphalt became a greater concern due to increased tire pressure, wheel loads, and traffic volume, and SMA mixtures began to be used again.
In the meantime, Sweden continued to allow the use of studded tires, and SMA mixtures have provided good performance under these severe loading conditions. Other European countries have used SMA mixtures with similar success. At least nine European countries are using SMA as a conventional wearing course with more than 1.09 million metric tons (1.2 million tons) of the mixture placed on motorways in the United Kingdom during 2001.
An FHWA-sponsored European study tour in the fall of 1990 brought this technology to the United States. The study group consisted of contractors and representatives from the National Asphalt Pavement Association (NAPA), Asphalt Institute, FHWA, and State highway agencies. The purpose of the trip was to observe the quality of roads and to discuss construction and contracting procedures. One of the items that most impressed the group was the performance of SMA mixtures. Based on the trip members' observations, FHWA decided to help support the construction of SMA test sections on U.S. highways to determine construction feasibility, performance, and cost-effectiveness.
Staff from FHWA's Turner-Fairbank Highway Research Center assisted States by providing information on SMA mix design, while FHWA's Mobile Asphalt Pavement Mixture Laboratory provided materials analysis onsite and support for quality control and compliance. NAPA, in cooperation with FHWA, published a series of documents on design and construction issues using the SMA mixture. In 1997, the National Cooperative Highway Research Program's (NCHRP) Designing Stone Matrix Asphalt Mixtures (Report 9-08) identified guidelines for the design and construction of SMA. The report is the basis of the current American Association of State Highway and Transportation Officials (AASHTO) specification.
Currently, more than 28 States use SMA as an asphalt pavement wearing surface. The Georgia DOT uses an open-graded friction course as a wearing surface over SMA on major freeways. Since 1992, Maryland has constructed 85 SMA projects totaling more than 2,093 kilometers (1,400 lane miles). SMA is specified exclusively in Maryland on high-speed roadways--89 kilometers (55 miles) per hour and higher--where traffic counts exceed 20,000 Average Annual Daily Traffic (AADT).
States using the mixture have found that rutting has been virtually eliminated on SMA surfaces, while reflective cracking has been greatly reduced. Improved durability--less stripping and raveling than conventional mixes--has been observed. The increased surface texture has reduced hydroplaning and spray. Overall, SMA mixtures have increased performance life significantly. A Canadian study indicated that the higher initial cost (20-25 percent) is more than offset by the reduction in rutting and the 30-40 percent decrease in thickness. FHWA estimates that approximately 45 million metric tons (50 million tons) of SMA have been placed on U.S. highways since 1991.
Air Void Analyzer
Air is a natural component of concrete but large air voids are undesirable. Some amount of entrapped air, consisting of tiny bubbles dispersed evenly throughout the concrete, is desirable for freeze-thaw resistance. Although entrained air improves workability, it also reduces compressive strength, so it must be kept under control.
For a concrete to be freeze-thaw durable, it typically needs to contain from 4 to 8 percent air by volume, uniformly dispersed in small bubbles throughout the volume of concrete. Onsite pressure-meter testing is used routinely to measure the total entrained air content. Although pressure meters are effective in determining total air content, they do not indicate how that volume of air is distributed throughout the concrete.
Even though research has shown that it is vital for adequate freeze-thaw performance to characterize the air void system in this manner, there currently are no standardized test methods to determine these properties on fresh concrete. The only standardized method to determine the air void system is to run a linear traverse or modified point count as prescribed in American Society for Testing and Materials' (ASTM) "Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete" (C-457). Unfortunately, these tests are performed on hardened concrete and typically take several days to complete, when the concrete most likely already has traffic on it. The tests are expensive and generally are performed to determine the cause of premature deterioration, not to prevent it.
The air void analyzer is a portable device that measures the entrained air void structure of fresh concrete in about 30 minutes. Test results correlate closely with ASTM C-457 values obtained on hardened concrete. The concrete producer or contractor can use the air void analyzer at the job site to adjust the mixture proportions and mixing procedures in real time, and these admixture adjustments can improve the air void structure dramatically and thus the concrete's freeze-thaw durability. Because the new technology can be used on fresh concrete and allows real-time evaluation, it helps to improve quality control and also speeds construction.
The air void analyzer, which was developed more than a decade ago by a European firm, is one of several technologies used by FHWA's Mobile Concrete Laboratory. The Kansas DOT has been using the analyzer technology since April 2001 and has developed a State specification. Kansas is working with FHWA to lead an effort by AASHTO's Technology Implementation Group to accelerate deployment of the air void analyzer technology. Implementation goals include developing a common standard test protocol, specification, and data collection form that all States could use, and identifying training needs and available resources.
Mammoet, an Innovative Transport Device
A Washington-Oregon project, renovation of the Lewis and Clark Bridge, involved installation of a new deck. Built in 1929, the historic steel truss bridge spans the Columbia River between Longview, WA, and Rainier, OR. To minimize impacts on the traveling public, the Washington State DOT committed to a tight construction window of 9:30 p.m. to 5:30 a.m. nightly, for 120 nights, rather than closing the entire bridge.
A total of 103 concrete deck panels were replaced, each measuring 11 meters (36 feet) wide by up to 14 meters (45 feet) long, and each weighing up to 81,720 kilograms (180,000 pounds). To remove and replace each panel took approximately 8 hours. Vehicles were able to drive on the new deck panels the day after installation. Benefits to the public include having the bridge open for normal daytime traffic--important due to the close proximity to the Port of Longview. The redecking will extend the life of the Lewis and Clark Bridge for another 25 years.
To replace the deck panels, the contractor employed an innovative approach. A large transport device produced by a Dutch company, Mammoet, was used to transport the new deck panels to the top of the bridge. The firm specializes in solving heavy lifting and transport challenges in the petrochemical and power generation industries.
The Mammoet hauler is 64 meters (210 feet) long and consists of a truss laying on its side with two low-profile "trucks," one supporting each end of the truss. Each truck has 24 axles with 2 to 4 wheels that rotate nearly 360 degrees. A single driver using a console and joystick operates the trucks. The truss spans a gap of more than 27 meters (90 feet) between the trucks, which allows the transport to carry two 14-meter (45-foot) deck panels at the same time. The transport itself weighs more than 122,580 kilograms (270,000 pounds), unloaded.
After being driven on top of the bridge, Mammoet picks up a panel that has been cut out, then rolls forward and lowers a replacement panel into place. Finally, Mammoet is driven off the bridge carrying the old panel and then repeats the process with each panel.
Self-Consolidating Concrete
In the early 1990s, Japan developed self-consolidating concrete (SCC), which does not require vibration to achieve full compaction, for bridge building and tunnel construction. An SCC mix has a high degree of workability and remains stable both during and after placement.
Self-consolidating concrete uses common ingredients, plus superplasticizers and viscosity modifiers. The mix must meet three key property requirements:
* Ability to flow into and completely fill intricate and complex forms under its own weight
* Capability to pass through and bond to reinforcement material under its own weight
* High resistance to aggregate segregation
Eliminating vibration cuts down on the labor needed and speeds up construction, resulting in cost savings and less disruption of traffic. It also reduces the noise level at construction sites. The overall concrete quality is improved, as problems associated with vibration are eliminated, including undervibration, overvibration, and damage to the air void structure.
Several European countries formed a consortium in 1996 to develop SCC for practical applications. Over the past 5 years, the Netherlands, Sweden, and the United Kingdom have constructed SCC bridges and structures. Sweden used SCC on the Sodra Lanken road in Stockholm, the largest ongoing infrastructure project in that country. The project will provide a 6-kilometer (3.7-mile) four-lane link from west to east in the southern part of the city. The highway includes seven major junctions, with bridges, earthen retention walls, tunnel entrances, and concrete box tunnels. Begun in 1998, the work is slated to wrap up in 2004.
One lesson learned from SCC projects in Europe and Japan is that the production of SCC requires more experience and care than that of conventional vibrated concrete. Although most common concrete ingredients and mixers can be used for producing SCC, mixes must be designed properly and tested to assure compliance with the project specifications. All commonly used form materials are suitable for SCC, but, during cold weather placement, insulating the framework to maintain the temperature and normal setting time may be necessary. During the hardening process, SCC is more sensitive to temperature and tends to dry faster than conventional vibrated concrete, because there is little or no water near the surface. The concrete should be cured as soon as practical after placement to prevent cracking due to surface shrinkage.
Roundabouts
Roundabouts are used extensively throughout Europe and in many other places around the world to reduce crashes, traffic delays, fuel consumption, air pollution, and construction costs, while increasing capacity and enhancing intersection beauty. "They have been used successfully to control traffic speeds in rural and urban settings and in residential neighborhoods," says Joe G. Bared, a highway research engineer in FHWA's Office of Safety Research and Development, "and are accepted as one of the safest types of intersection design."
A modern roundabout has three major characteristics compared to the traffic circles and rotaries that were its predecessors. First, in a modern roundabout, vehicles in the circular travel way have the right of way. This change on a national basis in England in 1963 marked the start of the modern roundabout era. Second, roundabouts are small, generally from 21 to 49 meters (70 to 160 feet) in diameter compared with 91.5 to 122 meters (300 to 400 feet) for traffic circles and rotaries. Third, roundabouts have a raised entry "splitter" island that slows vehicles just before entry, duplicating in a sense the curvature that the drivers will experience within the roundabout itself.
In 1990 the modern roundabout arrived in the United States in Summerlin, a planned community on the west side of Las Vegas, NV. With rapid growth of the surrounding community, daily traffic increased from very low flows to about 7,000 vehicles in the north roundabout and to about 11,000 vehicles in the south roundabout. Only four crashes have been reported at the two roundabouts over their 5-year history.
When the first roundabout freeway interchange in the Nation was built in 1995 at the I-70 interchange in Vail, CO, roundabouts then numbered about a dozen nationally. At Avon, CO, which is the next I-70 interchange west of Vail, five roundabouts were installed in 1998 between the I-70 interchange and the Beaver Creek Mountain ski resort.
The first modern roundabout on the California State highway system was installed by the city of Santa Barbara in 1992. The roundabout replaced an intersection of five two-lane streets regulated by stop signs. The old intersection averaged four crashes per year. Since installation of the roundabout, crashes have averaged 2.1 per year, with only five reported in a 28-month period.
Maryland's first roundabout was built in April 1993 in Lisbon. Measuring 31.5 meters (103 feet) in diameter, the roundabout replaced a lightly traveled four-leg intersection regulated by a flashing beacon. The former intersection had averaged eight crashes with eight personal injuries per year. Two crashes occurred in the first 3 months after construction of the roundabout, resulting in two personal injuries. For the following 21 months, there were no reported crashes.
Roundabouts have been constructed in practically every State, including Alaska and Hawaii. Today, the number of modern roundabouts in the United States has leaped to around 800.
"We anticipate that roundabouts will be built in the United States by the hundreds annually in the coming years," says Bared, "and by the thousands annually early in the 21st century." If so, the increase will duplicate the trends that took place first in Britain and Australia during the 1970s and 1980s, and now being repeated throughout western Europe.
Moving Forward
The previous examples are merely a taste of the type of innovation that is possible through a new business model for designing, building, and maintaining highways. Although finding and effectively distributing innovations and technology will be critical to the success of such a model, the true barometer will be how well the highway community as a whole can come together effectively as partners to support the need for such a new model and to spread the word on new approaches. Thus, the key will not be, "What if I ...," but rather, "What if we ..."
Ultimately, what may be responsible for getting the highway community to adopt a better mousetrap sooner rather than later is in creating a proper environment where new mousetraps are appreciated.
Byron N. Lord is a program coordinator in FHWA's Office of Infrastructure. Lord has more than 30 years of experience with FHWA and has served as chief of the Pavement Division in the Office of Research, as chief of the Infrastructure Division in the Office of Technology Applications, and recently as deputy director of the Office of Pavement Technology. He has bachelor's and master's degrees in civil engineering from the Citadel and West Virginia University.