Today’s highways perform differently from those of the 1960s and 1970s. There are about 3½ times as many vehicles on the roads as there were in the 1960s, and the road network itself is more extensive and incorporates features aimed at expediting traffic flow and reducing risks to users. Thirty years ago, a driver crossing narrow medians of an Interstate highway had a good chance of avoiding conflict with vehicles in the opposing lanes because of light traffic, but today, chances are high that a collision with another vehicle would result. Experience in Missouri has demonstrated the effectiveness of median cable barriers, which catch and decelerate a vehicle and prevent it from entering the opposing lanes. The installation of 179 miles of median cable barrier on Interstate 70 reduced cross-median fatalities by more than 90 percent, from 24 in 2002 to two in 2006 (Chandler 2007). Many states subsequently expanded their use of median barriers as a highly effective safety measure.
Other highway innovations may be less visible to users but have been useful in allowing those responsible for the nation’s roads to improve overall performance in a period of constrained budgets. Examples include new bridge and pavement materials that require less frequent maintenance and renovation and that have longer service lives, thereby reducing operating costs. New materials and innovative construction techniques have also resulted in more effective ways of building new roads and bridges and of rehabilitating aging infrastructure and in environmental benefits. For example, experience in Virginia has shown that the lower temperatures and reduced fumes associated with warm-
mix asphalt are advantageous for work crews during paving, while the reduced energy consumption during production and reduced plant emissions offer further advantages compared with hot-mix asphalt (Diefenderfer and Clark 2011).
In addition to the benefits gained through technological innovations, innovative procurement strategies have allowed state departments of transportation (DOTs) to reduce considerably the overall duration of major construction projects without compromising the quality of the final product and allowed private contractors more opportunities to introduce innovative processes and products. A better understanding of the behavior of travelers in general, and highway users in particular, has informed the development of transportation policies and helped make more effective use of the most congested parts of the nation’s highway network.
RD&T has fueled innovation across the nation’s road network since the early 1950s, when the nation’s highway organizations joined forces to develop advances in pavement design (TR News 1996). Today, a wide variety of research activities are conducted under the auspices of programs responding to the needs of the numerous jurisdictions responsible for the highway system (see Chapter 3). These activities cover numerous disciplines and range from investigations aimed at gaining more comprehensive knowledge and understanding of a subject (e.g., the relationship between a pavement material’s properties and its composition), through the design and development of prototypes and processes (e.g., robust, low-cost transponders for road pricing applications), to practical implementation of research results (e.g., the incorporation of advanced design and measurement techniques into state DOT construction standards).
The federal government plays a major role in the national RD&T enterprise, both through its support of research conducted by other organizations (such as universities and contractors)
and through its own RD&T activities. FHWA has been instrumental in furthering innovation in the highway sector, as illustrated by the examples in the following section.
HIGHWAY INNOVATIONS FOSTERED BY FHWA
Doing More with Less: Stronger Bridge Materials Result in Major Cost Savings
When Hurricane Katrina made landfall in Louisiana on August 29, 2005, the accompanying storm surge severely damaged the I-10 Twin Span Bridge across Lake Pontchartrain, which links New Orleans and Slidell. Rising water and battering waves shifted a number of the bridge’s 255-ton concrete spans off their piers and misaligned others, leaving the 5½-mile structure impassable. Emergency repairs allowed a phased reopening of the bridge between October 2005 and January 2006, but because I-10 is a vital transportation artery, the Louisiana Department of Transportation and Development (DOTD) decided that the repaired structure needed to be replaced by a new, more robust bridge capable of withstanding surges driven by hurricane-force winds (Lee and Hall 2011). Construction of the new $800 million bridge began in August 2006 and was completed in September 2011. The project took advantage of a new high-strength, high-performance concrete (HPC) material offering improved performance and an accompanying reduction in cost.
To help overcome concerns about the use of new HPC materials for bridge construction, FHWA’s HPC Technology Delivery Team, created in 1997, has assisted a number of state DOTs in the design and construction of HPC bridges and encouraged others to try HPC in their highway bridges (FHWA 2005). The team’s goal is to improve the durability and cost-effectiveness of the nation’s transportation infrastructure through the use of HPC and to educate users about topics such as structural design and specifications, mix design and proportioning, and costs (for example, see Russell et al. 2006).
The Louisiana DOTD has gradually been introducing high-
strength HPC into its bridge construction program to develop an in-depth understanding of how this material behaves in the field. For example, the successful construction of the Charenton Canal Bridge, which opened to traffic in 1999, demonstrated that an HPC bridge could be designed and built in Louisiana with the use of locally sourced materials to limit transportation costs (LTRC n.d.). Use of HPC on the new I-10 Twin Span Bridge saved a minimum of $16 million because of the need for less concrete and fewer girders (LTRC n.d.). In addition, the Louisiana DOTD expects the new bridge to have a minimum service life of 75 years instead of the standard 50-year service life for concrete structures because the new concrete is less permeable to water and thus more resistant to environmental degradation. The extended service life will provide savings in life-cycle costs over and above the savings in construction costs.
Diverging Diamond Interchange: Quicker, Cheaper, Safer
With increasing traffic volumes, congestion has worsened at many highway junctions. As a result, drivers, pedestrians, and cyclists experience longer delays and greater risks when they cross busy intersections. To address these issues, FHWA researchers are exploring innovative designs with the potential to alleviate congestion and enhance safety at intersections and interchanges.
One of FHWA’s researchers heard a talk about an innovative interchange concept at a 2003 symposium and, inspired by the findings, set out with colleagues at the Turner-Fairbank Highway Research Center (TFHRC) to study how the diverging diamond interchange (DDI) might work.1 Models indicated that, by moving through traffic and left-turning vehicles to the left side of the road at highway intersections through signalization, the design offers operational, safety, environmental, and cost benefits. FHWA’s driving simulator experiments at TFHRC further confirmed the potential safety benefits, even for drivers
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1 See the diverging diamond interchange website: http://www.divergingdiamond.com.
unfamiliar with the new interchange design, and allowed engineers to address problems with sight distance that might not have been noticed otherwise (FHWA 2007).
The first DDI in the United States, located at I-44 and MO-13 in Springfield, Missouri, was completed in June 2009. The project aimed to alleviate congestion on the heavily traveled Kansas Expressway (MO-13) at I-44, which historically had mile-long traffic backups and serious left-turn crashes. By rehabilitating the MO-13 bridge over I-44, Missouri DOT was able to complete construction in 6 months at a cost of $3.2 million. In contrast, a conventional interchange would have required a new, much larger bridge, which would have raised the cost to about $10 million and the construction time to 12 to 18 months (Bared and Saiko 2010). Important safety benefits were realized almost immediately, with an 80 percent reduction in injury crashes and a 53 percent reduction in all crashes in the first year of operation (McCarthy et al. 2013).
More than 30 DDIs have been built in the United States since 2009. State DOTs and other jurisdictions across the country have realized important savings in cost and construction time, and road users have enjoyed fewer delays and improved safety. Meanwhile, FHWA researchers continue to evaluate the impacts of DDIs and identify strategies to improve safety and accommodate pedestrians and cyclists (FHWA 2014b).
Design–Build Project Delivery: Shortening the Time from Concept to Concrete
In the mid-1990s, during preparation for the 2002 Winter Olympics in Salt Lake City, the Utah DOT was under pressure to reduce the time needed to complete its I-15 corridor reconstruction project. Mindful not only of the high-profile Olympic deadline but also of the public’s desire to minimize the period of severe traffic congestion accompanying the construction work, the Utah DOT decided to use a contracting method known as design–build (DB) to expedite the project and speed construction.
At the time, a number of state DOTs were testing and eval-
uating alternative contracting methods, including DB, under FHWA’s Special Experimental Project Number 14 (SEP-14)—Innovative Contracting. SEP-14 was established in 1990 with the objective of exploring opportunities for expediting highway projects through the use of alternatives to the traditional design–bid–build (DBB) contracting approach. Under DBB, design and construction are conducted sequentially under two separate contracts, and cost is the single criterion determining the winning bid. In contrast, under DB, the design and construction phases of a project are combined into a single contract, which is usually awarded on either a low-bid or a best-value basis. By eliminating the need for a second procurement process and allowing for some overlap of design and construction (activities that are conducted sequentially under DBB), DB can reduce overall project duration, sometimes considerably. In addition, use of a best-value criterion for contract award allows state and local agencies to consider a range of factors, including social and economic impact, safety, public perception, and life-cycle costs.
The Utah DOT’s I-15 project was one of about 300 transportation projects proposed for DB contracting under SEP-14; located in 32 states, the projects were worth nearly $14 billion. The project outcomes confirmed the time-saving advantages of DB. By 2002, for example, the Florida DOT had awarded 49 DB projects for nearly $500 million worth of work and estimated that DB cut the traditional delivery period by 30 percent (Gransberg et al. 2008). The Utah DOT’s I-15 project also demonstrated the benefits of DB for large highway projects. Construction on the $1.63 billion project began in April 1997 and was completed 4 years 4 months later, in July 20012—a major time saving compared with the estimated 10 years needed to complete the project under traditional contracting methods.3
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2 Project Profiles, I-15 Corridor Reconstruction Project. FHWA Office of Innovative Program Delivery (http://www.fhwa.dot.gov/ipd/project_profiles/ut_i15_corridor.aspx).
3 Bolling, D. Undated. An Innovative Contracting Overview. PowerPoint presentation available at http://www.ic.usu.edu.
FHWA conducted a comprehensive national study evaluating the effectiveness of DB contracting in response to a request in the 1998 Transportation Equity Act for the 21st Century (SAIC et al. 2006). By analyzing DB projects completed under SEP-14, the agency was able to assess the impacts of DB on project duration, cost, and quality and was able to provide guidance to transportation agencies about the types of project likely to benefit from a DB approach. The knowledge gained from SEP-14 projects has helped institutionalize the DB contracting process, which was rarely used by state DOTs 15 years ago but is now a common approach for saving time on large highway construction projects.
Road Pricing Offers Opportunities to Manage Congestion
Congestion in many major metropolitan areas of the United States has become a growing source of frustration for motorists, with those traveling at peak times sometimes needing to allow 60 minutes for trips that take only 20 minutes in lighter traffic (TRB 2013). There are now more than 250 million registered highway vehicles on U.S. roads, a number that has grown by more than one-third over the past 20 years.4 Opportunities to expand highway capacity to accommodate these vehicles are limited by construction costs, which average $10 million per new lane mile in urban areas (FHWA 2006), and by the need to avoid adverse impacts on local communities.
More than 50 years ago, Nobel Prize–winning economist William Vickery suggested managing traffic congestion by charging drivers more to use overcrowded roads at peak times. Customers have long been used to paying more for hotel rooms, airline tickets, and electricity when demand is high, but in the 1960s the idea of point-of-sale charges for roadway use conjured up visions of “a clutter of toll booths, an army of toll collectors, and traffic endlessly tangled up in queues” (Vickery 1963). However, Vickery suggested that “with a little ingenuity, it [might be] pos-
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sible to devise methods of charging for the use of city streets that are relatively inexpensive, produce no interference with the free flow of traffic, and are capable of adjusting the charge in close conformity with variations in costs and traffic conditions.”
Today, technological innovation has allowed Vickery’s vision of traffic flowing freely through an adaptive charging system to become a reality with the implementation of all-electronic tolling and dynamic pricing on express lanes, also known as high-occupancy toll (HOT) lanes. Examples include the I-95 and I-495 express lanes in Virginia; the SR-91 express lanes in Orange County, California; the I-15 HOT lanes in San Diego, California; and the I-394 express lanes in Minnesota. An antenna above a “priced” lane communicates with a transponder (e.g., an E-ZPass tag) in a vehicle, collecting information that allows each vehicle to be identified and the toll charged to a particular customer.
However, demonstrating that pricing is effective in reducing congestion and can gain public acceptance is a separate challenge. In 1991, the Congestion Pricing Pilot Program [renamed the Value Pricing Pilot Program (VPPP) in 1998] was established by Congress to demonstrate whether and to what extent roadway congestion can be reduced with pricing strategies. As part of this program, FHWA entered into agreements with states and cities to explore strategies for managing congestion, including tolling demonstrations. Between 2008 and 2012, approximately $65 million in federal funding supported value pricing projects in 12 states (California, Connecticut, Florida, Illinois, Maryland, Minnesota, New Jersey, North Carolina, Oregon, Texas, Virginia, and Washington) and in two cities (New York City and Washington, D.C.).
Projects and studies conducted under the VPPP have provided many valuable lessons.5 Most important, they have demonstrated that congestion can be reduced in highway corridors
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5http://www.ops.fhwa.dot.gov/congestionpricing/value_pricing/index.htm.
when pricing is implemented. For example, peak-hour traffic on the SR-91 express lanes in Orange County, California, typically moves at more than 60 mph, whereas traffic on the unpriced lanes travels at average speeds of 15 mph or less. Thus, travelers on the express lanes can save as much as half an hour on a single 10-mile trip at peak times (FHWA 2006).
Road pricing proposals have frequently raised equity concerns because of the fear that low-income drivers may be priced off the road. However, broad generalizations about the fairness of priced lanes are misleading (TRB 2011), and lessons from the VPPP indicate that equity concerns are being addressed through better planning and public outreach. Moreover, experience has shown that motorists across all income groups are willing to pay for a faster, more predictable, and stress-free ride that gets them to work, medical appointments, and child-care pickup on time and that frees more personal time for friends, family, and recreational activities (FHWA 2006).
While the concept of road pricing has been present for more than half a century, FHWA’s work with states and cities through the VPPP has been essential in demonstrating that pricing is now a practical and widely acceptable option for managing congestion.
The federal government, through FHWA, has played a vital role in providing the steady stream of innovations needed to support improvements in the nation’s highways. Today’s roads are faster, safer, and greener than those of the 1960s and 1970s, in large part because of FHWA’s RD&T activities and those of other research organizations that FHWA has promoted through technology transfer. In addition to performing its own research and supporting research conducted by others, the agency has coordinated activities across the complex and diverse highway RD&T enterprise. It has been instrumental in encouraging the risk-averse public-sector organizations responsible for the
nation’s roads to embrace innovations that offer benefits for users and infrastructure owners alike.
Strategies that have proved effective in the past cannot guarantee future success. Nonetheless, it appears highly likely that FHWA, if provided with the appropriate resources, can continue to play a vital role in fostering the innovations needed in meeting the challenges of the highway system of the 21st century. The various organizations conducting highway RD&T are described in Chapter 3, and some of the innovations, and FHWA’s anticipated role in their development and implementation, are described in Chapter 4.
