U.S. Department of Transportation
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: FHWA-HRT-17-003 Date: March/April 2017|
Publication Number: FHWA-HRT-17-003
Issue No: Vol. 80 No. 5
Date: March/April 2017
FHWA’s Every Day Counts program promotes proven but underutilized technologies to advance the transportation sector. Take a look at five successful initiatives from the four rounds of the program.
|A road diet in Washington, DC, enabled the District Department of Transportation to add protected bike lanes in both directions along Pennsylvania Avenue. Road diets are one of five successful safety innovations championed by FHWA’s Every Day Counts initiative and are included in EDC-4 with several other pedestrian safety countermeasures.|
Increasingly, the transportation industry faces challenges from tightened budgets and the need for greater accountability and transparency. Highway agencies need effective tools and methods to make roads safer and last longer, reduce the use of resources, and decrease project delivery times. Since 2009, the Federal Highway Administration’s Every Day Counts (EDC) initiative, now in its fourth round, has worked to meet these needs and challenges.
The EDC initiative is a cooperative effort involving FHWA, the American Association of State Highway and Transportation Officials, and other stakeholders in the public and private sectors to advance a culture of innovation in the transportation community. Through this collaborative, State-based effort, the partners advance the rapid deployment of proven, market-ready strategies and technologies to shorten the project delivery process, enhance roadway safety, reduce congestion, and improve environmental outcomes. Designed to complement other initiatives centering on innovative technologies, practices, and investments, EDC plays an important role in helping transportation agencies fulfill their obligation to deliver the greatest value for the tax dollars spent.
In each of the program’s 2-year cycles, FHWA works with State transportation departments, local governments, tribes, private industry, and other stakeholders to identify a new set of innovative technologies and practices that merit widespread deployment. Once innovations are selected, State Transportation Innovation Councils work to bring together stakeholders from the public and private sectors to evaluate innovations and spearhead their deployment in each State.
“EDC’s collaborative, State-based approach to deploying innovation enables States to decide which innovations will work best for them and their customers,” says Tom Harman, director of FHWA’s Center for Accelerating Innovation.
Five safety innovations were promoted during the first three rounds of EDC: the SafetyEdgeSM in round 1 (2011–2012), intersection/interchange geometrics and high-friction surface treatments in round 2 (2013–2014), and road diets and data-driven safety analysis in round 3 (2015–2016). These last two are being continued in EDC-4 (2017–2018), with road diets included as one of five pedestrian safety countermeasures promoted under the Safe Transportation for Every Pedestrian initiative.
The development of the SafetyEdge is an excellent example of how two engineering disciplines--safety and pavements--came together to solve a problem. Pavement edge dropoffs have been linked to many serious crashes from roadway departures, including fatal crashes. To mitigate vertical dropoffs, FHWA advocates installing the SafetyEdge on pavements during paving or resurfacing.
Researchers at Northwestern University in Illinois first identified the problem of pavement edge dropoff as early as 1959, and studies by California and Texas in the 1970s and 1980s further quantified the problem. Although researchers in the 1980s documented the solution of a 45-degree angled wedge, most States failed to find a construction process that did not result in breakage, causing the same dropoff problem and requiring constant maintenance.
|An engineer measures the angle of a SafetyEdge application on a roadway in Shawano, WI.|
In 2003, maintenance engineers with the Georgia Department of Transportation, along with two FHWA experts (one in safety and one in pavements), pursued the constructability issue. Their efforts resulted in a 30-degree taper and the basic device that could form the shape in a way that is durable, does not slow down the paving process, and costs very little in extra effort or materials. However, the new technology and the safety benefits it offers did not gain traction among State transportation agencies until FHWA committed significant resources to pursue change.
FHWA’s EDC initiative and its predecessor, Highways for Life, gave the SafetyEdge technology the visibility needed to spread the word at leadership levels in State DOTs and to a wider audience in a short period. The EDC initiative was critical in convincing many agencies to acknowledge the problem of pavement edge dropoffs and that the SafetyEdge could not only solve it, but could do so at almost no cost--and likely extend the life of pavements by improving density at the pavement edge, which makes the pavement more durable. Because edge raveling is reduced, the roads may require less frequent maintenance.
|Diverging diamond interchanges, like the one shown here from above on I–15 in Utah, reduce the conflict points between different directions of traffic, resulting in fewer crashes.|
For FHWA, partnering with State and local agencies, as well as Local Technical Assistance Program centers, to make devices available and host open houses and demonstrations was critical to spurring widespread adoption, as was involving the paving equipment industry. For example, when the West Virginia DOT approached a paving contractor about including the SafetyEdge on a project, the contractor was able to apply the technique immediately because it had recently purchased a new paver that came equipped with the necessary device.
Prior to EDC, no States (and only one district in Georgia and a few counties in the country) had used the SafetyEdge as a standard practice. At the end of the first round of EDC, 36 State DOTs had adopted a standard specification with the SafetyEdge or some equivalent design.
Intersection and Interchange Geometrics
Intersections and interchanges are points of conflict where vehicles, pedestrians, and bicyclists cross paths or change direction--inherently resulting in conditions that can lead to serious crashes. More than 25 percent of annual highway fatalities in the United States occur at intersections or are intersection related. For crashes that result in injury but no fatality, intersections represent closer to half of the safety challenge.
To address that situation, the second round of EDC promoted alternative intersection and interchange designs, selected for their underutilization and potential for improving safety for all users while also reducing congestion.
A common characteristic among alternative intersection and interchange geometries is reduced or modified conflict points, particularly those associated with left turns across opposing traffic, facilitating simplified decisionmaking and safer movements through intersections by motorists, pedestrians, and bicyclists. EDC-2 focused on five design configurations under the umbrella of intersection and interchange geometrics: modern roundabouts, diverging diamond interchanges, displaced left-turn intersections, median U-turn intersections, and restricted crossing U-turn intersections.
The relationship between the geometry of the intersection and the type of traffic control used--whether yield, stop, or signal--can be optimized by improving the choreography of movement across the intersection. Although some of these geometric designs may seem complex or even counterintuitive, results from field studies and research demonstrate that users are able to navigate them effectively.
|EDC-2 Intersection and Interchange Guides|
|Displaced Left Turn Intersection Informational Guide (FHWA-SA-14-068)||http://safety.fhwa.dot.gov/intersection/alter
|Diverging Diamond Interchange Informational Guide (FHWA-SA-14-067)||http://safety.fhwa.dot.gov/intersection/alter
|Median U-Turn Intersection Informational Guide (FHWA-SA-14-069)||http://safety.fhwa.dot.gov/intersection/alter
|Restricted Crossing U-Turn Intersection Informational Guide (FHWA-SA-14-070)||http://safety.fhwa.dot.gov/intersection/alter
Increased safety and reduced congestion at intersections also can provide economic benefits to businesses and communities. The potential economic benefits, combined with improved safety, mobility, and maintained access to properties near intersections and interchanges, make alternative designs attractive transportation solutions for communities of all sizes.
The efforts under EDC to encourage the use of innovative intersections increased the momentum on several fronts. The use of roundabouts had been increasing to varying degrees for many years, but the design needed a coordinated push to achieve widespread acceptance. Similarly, despite a spike in interest in diverging diamond interchanges prior to EDC-2, a majority of States remained hesitant because of limited data on their use and results. And a lack of authoritative guidance hampered further progress on innovative intersection designs such as restricted crossing U-turn intersections, displaced left-turn intersections, median U-turn intersections, and others.
The EDC initiative focused the scattered and uncoordinated progress and experience into a unified effort. Through the partnership framework with AASHTO members and other stakeholders, planners and engineers received the resources to advance the state of the practice and create a legacy of experience that would sustain progress for innovative intersections beyond EDC-2. The effort included a series of informational guides, which are comprehensive planning and design resources for each of the different designs.
FHWA conducted training workshops and presentations and provided technical assistance, resulting in well over 1,000 professionals from dozens of States being educated about innovative designs. The EDC focus also resulted in outreach and educational materials such as videos and brochures, case studies, proceedings from the Transportation Research Board’s Alternative Intersections and Interchanges Symposium held in July 2014, and a robust program of continuing research and evaluation of innovative intersections and interchanges. For more information, visit http://safety.fhwa.dot.gov/intersection.
After EDC-2, the number of States (including Puerto Rico) actively implementing 2 or more of the 5 design configurations increased from 16 to 39, with 7 States reporting that they have made it a standard practice to consider alternative designs for all projects.
High-Friction Surface Treatments
Horizontal curves make up only a small percentage of U.S. highway miles but are the sites of more than 25 percent of highway fatalities in the Nation each year. Historically, highway agencies have used two approaches to reduce crashes at horizontal curves. The first, involving the redesign of the curve’s geometry, is expensive. The second, installing low-cost solutions such as signing, markings, and rumble strips, may address issues of driver error.
High-friction surface treatment (HFST) offers an innovative third solution. This low- to moderate-cost alternative can help significantly reduce crashes on these curves.
The deterioration of pavement surface friction can be a contributing factor to crashes on horizontal curves because vehicles need more friction in a curve to change the trajectory than on other sections of the road. At locations such as sharp horizontal curves and ramps, approaches to intersections, and downgrades where vehicles may brake excessively, the road surface of standard pavements may become prematurely polished, reducing the available pavement friction. HFST technology offers an overlay option that supplies more friction than traditional overlays and maintains that friction for a much longer time.
HFST is a thin layer of specially engineered, durable, high-friction aggregates applied as a topping on resins or polymers--usually urethane, silicon, or epoxy--with a binder. These aggregate systems have long-lasting skid resistance and make the overlay much more resistant to wear and polishing. HFST can be installed using any of the three main application methods: fully automated, semiautomated, and manual. However, mechanical installation is preferred as it requires much shorter installation time, reduces secondary crash exposure, and ensures a higher quality application.
|High-friction surface treatments, such as the one applied on this curve on a rural road in Thurston County, WA, are a low-cost method to reduce crashes and improve safety without redesigning a road’s geometry.|
The resin or polymer binder combination locks the aggregate firmly in place, creating an extremely rough, hard surface capable of withstanding everyday roadway demands, such as heavy braking and even snowplowing. When applied by maintenance crews, HFST restores pavement surfaces where high traffic volumes have worn down existing surface aggregates. The treatment also can serve as an alternative that compensates for substandard geometric designs, such as sharp curves and inadequate superelevation (the transverse cross slope designed to counter centrifugal force at a curve, preventing a vehicle from departing the roadway).
European countries have been using HFST as a standard practice for decades. The United Kingdom first evaluated the concept of applying skid-resistant surface treatments in the 1960s. After a successful trial near London, the treatments were used widely and now are required on certain curves, roundabouts, and intersection approaches. Other countries also began to apply HFST, and a 1976 U.S. study found a 31-percent reduction in crashes at intersections with the treatments. By the early 2000s, a handful of States had implemented surface treatments at curves, but transportation agencies were not using the method widely when it was selected as an EDC-2 innovation.
|Road crews apply durable, high-friction aggregates like this with resin or polymer binders to reduce crashes on horizontal curves.|
The EDC-2 campaign established goals to accelerate HFST deployment and adoption. The team created a plan to serve as a roadmap for rapid implementation, including technical guidance and assistance, benchmarking, marketing and communications, training, and project demonstrations to highlight notable practices. The effort included fact sheets, brochures, and videos; case studies; and specifications developed in partnership with AASHTO and the American Traffic Safety Services Association’s High Friction Surfacing Council.
Before-and-after evaluations of HFST applications show positive safety benefits. Kentucky placed HFST on 26 curves and, to date, has seen an average reduction from 6.2to 1.9 crashes per year at those locations. The Marquette Interchange in Milwaukee, WI, experienced 219 crashes in the 3 years prior to HFST installation. A study after the installation in 2011 found a total of nine reported crashes in the following 3 years. A recent before-and-after study from the South Carolina DOT on a series of HFST installations on horizontal curves indicates a benefit-cost ratio of 24 to 1.
Other benefits of HFST include negligible environmental impacts, reduced construction time and cost compared to other solutions, and minimal effect on traffic from the rougher surface. In addition, project installations for HFST are brief, and the materials set up quickly, so the treatments often can be applied in hours, requiring minimal impact on traffic during installation compared to a conventional pavement overlay project.
By the end of the 2-year EDC cycle, the number of States using HFST grew from 14 to 37 States, plus Washington, DC, and Puerto Rico. Fourteen States have made the use of HFST a standard practice for reducing crashes at critical locations.
Historically, adding lanes and widening roads has been one of the preferred solutions for reducing traffic congestion. However, the complete streets movement has brought an alternative: the road diet. A road diet is a roadway reconfiguration that typically involves narrowing or eliminating one or more traffic lanes and adding bicycle lanes and improved pedestrian facilities (such as sidewalks).
The reconfiguration offers several high-value improvements at a low cost when applied to traditional four-lane, undivided roadways. The primary benefits include enhanced safety, mobility, and access for all road users to accommodate a variety of transportation modes. A classic road diet involves converting an existing four-lane, undivided roadway segment to a three-lane segment consisting of two through lanes and a center, two-way left-turn lane. FHWA advises that roadways with average traffic volumes of 20,000 vehicles or less per day may be good candidates for a road diet and should be evaluated for feasibility.
Studies show that road diets result in an estimated crash reduction of 19 to 47 percent, reduced vehicle speed differential in the traffic flow, and integration of the roadway into surrounding uses that offers residents, businesses, and visitors an enhanced quality of life. A key feature of a road diet is that it enables reclaimed space to be allocated for other uses, such as turn lanes, bus lanes, pedestrian refuge islands, bike lanes, sidewalks, bus shelters, parking, or landscaping.
In January 2012, FHWA designated road diets as a proven safety countermeasure and a safety-focused design alternative to traditional four-lane, undivided roadways for certain applications. In 2015, FHWA selected road diets as an EDC-3 innovation, and it continues as a subset of an overarching pedestrian focus in EDC-4.
“With a road diet, pedestrians can be safely accommodated,” says Becky Crowe, a transportation specialist in FHWA’s Office of Safety. “The road diet program [that] started in EDC-3 will continue into EDC-4 through the Safe Transportation for Every Pedestrian [STEP] initiative. Road diets, along with four other countermeasures, will be advanced to improve pedestrian safety.” The other measures under STEP are pedestrian hybrid beacons, pedestrian refuge islands, raised crosswalks, and crosswalk visibility enhancements, such as lighting, signing, and marking.
As more communities desire complete streets and more livable spaces, they look to transportation agencies to find opportunities to better integrate pedestrian and bicycle facilities and transit options along their corridors. When an agency implements a road diet in conjunction with reconstruction or simple overlay projects, the safety and operational benefits are achieved essentially for the cost of restriping. FHWA is working closely with State and local agencies to develop guidance on road diet applications, perform feasibility studies, and support local and State marketing efforts.
Road diets have been implemented by transportation agencies for more than three decades, but only recently have they received serious consideration as a design alternative. By the end of EDC-3 in December 2016, half of the States had plans to make road diets a standard practice.
In Arizona, for example, Phoenix is implementing a comprehensive bicycle master plan and complete streets ordinance. Both projects rely heavily on road diets to improve safety and accommodate bicyclists and pedestrians. Utah’s largest metropolitan planning organization, Wasatch Front Regional Council, added road diets to the toolbox of solutions that member towns can request assistance for under the Local Planning Resource Program. And the Virginia DOT’s Northern Virginia District is close to institutionalizing road diets. Since 2010, the department has installed 15 road diets, 5 of them added in Fairfax County during the summer of 2015 alone.
|This road diet in Honolulu, HI, converted a road with two lanes in each direction to one lane in each direction with a shared center turn lane, dedicated bike lanes on each side, and parking for the residential neighborhood.|
In 2014, FHWA developed the Road Diet Informational Guide (FHWA-SA-14-028) to help communities understand the benefits of road diets and assist agencies in determining whether they are a good fit for certain corridors. In 2015, FHWA published Road Diet Case Studies (FHWA-SA-15-052) to provide stakeholders with examples and advice that can guide them in implementing road diets in their own jurisdictions. That same year, FHWA developed the Road Diet Desk Reference (FHWA-SA-15-046) to provide a quick overview of all the benefits associated with road diets.
During the EDC-3 promotion of road diets, 18 States institutionalized the use of road diets, exceeding FHWA’s target of 15 States by September 30, 2016.
Data-Driven Safety Analysis
“How many crashes on a roadway are beyond what’s expected from an engineering perspective?” This question has plagued transportation professionals for years. Now, there are methods to answer it.
With limited funding available to address transportation needs, highway professionals are constantly challenged to make decisions that maximize the return on investment. Evaluating a roadway in terms of generally accepted guidelines is no longer sufficient. Decisionmakers need to determine whether a roadway will perform satisfactorily in terms of crashes now and into the future--and to do this, they need data.
The data-driven safety analysis innovation has been championed under EDC-3 and again in EDC-4. It is the application of predictive and systemic analysis approaches to safety management and project development to support improved decisionmaking and more efficient, effective investments, resulting in fewer severe crashes.
Predictive analysis. Predictive analysis approaches combine crash, roadway inventory, and traffic volume data to provide more reliable estimates of the expected safety performance of an existing or proposed roadway. The results inform decisionmakers on how to manage roadway safety and project development as well as select and evaluate safety countermeasures. Predictive analysis enables planners to determine, among possible design alternatives, which might have the greatest reduction of fatal and injury crashes.
Examples of tools that State and local highway agencies can use to apply predictive approaches include AASHTO’s Highway Safety Manual, AASHTOWare Safety Analyst™ software, FHWA’s Interactive Highway Safety Design Model (IHSDM), the National Cooperative Highway Research Program’s Enhanced Interchange Safety Analysis Tool (ISATe), FHWA’s Crash Modification Factors Clearinghouse, State-developed tools, and several commercial products available in the marketplace.
Before the development of predictive methods, agencies had no way to quantify the anticipated safety impacts of transportation decisions. This knowledge gap made it hard to fully evaluate safety impacts alongside criteria such as environmental and operational effects. Agencies also faced challenges when comparing treatments to spot locations and corridors to determine which ones had the greatest potential to reduce fatal and serious injury crashes.
Using predictive analysis, highway planners can determine which of three potential roadway designs should result in the fewest crashes and injuries. Here, the estimate for the existing roadway configuration is 110 fatal and injury crashes per year. For the first alternative, the estimate is 65 crashes and for the second alternative, 45 crashes.
In 2010, AASHTO published its Highway Safety Manual, an authoritative resource for both crash prediction models and crash modification factors for segments of two-lane rural roads, rural multilane highways, urban/suburban arterials, and intersections on all of those roads. In 2014, AASHTO added models for freeways, interchanges, and ramps to the previous set of prediction models, creating a comprehensive toolbox of evidence-based models to predict safety performance in terms of crash frequency and severity.
Systemic analysis. Systemic analysis approaches employ a systemwide screening of a roadway network based on the presence of high-risk roadway characteristics associated with particular severe crash types. Examples of such features include shoulder width, horizontal curvature, roadside rating, and intersection skew. This approach can be particularly helpful when a significant number of crashes occur over a wide area, such as in States with an extensive rural or local roadway system. Systemic analysis also can be applied to investigate specific severe crash types such as horizontal curve, cross-median, and pedestrian crashes. A comprehensive safety management program incorporates a systemic approach to complement traditional site analysis (or “hot spot”) approaches.
Previously, agencies largely relied on simple analysis of hot spot sites. Although high-crash locations do exist, many times the hot-spot treatment approach led agencies to make high-cost improvements at a limited number of locations. Often, locations that were at risk of severe crashes had to wait for a crash to happen before they could be treated. This approach to treating high-crash locations led many States to fund only projects on high-volume roads, often on the State-owned system. Using a systemic approach, however, States can better understand and quantify safety risks without having to rely solely on crash experience, providing an opportunity to improve safety performance across their road networks.
For example, in identifying locations for a cable median barrier along a divided roadway, an agency could determine where to install the barrier based solely on historical data on fatal crashes. However, these investment decisions would benefit from looking at the issue from a crash risk perspective. Roadway characteristics such as median width, horizontal curvature, traffic volume, number of traffic lanes, and proximity to access points can all greatly affect safety performance. Conducting a systemic safety analysis by reviewing the impacts that these features have on safety performance enables an agency to make informed investment decisions.
Under EDC-3, FHWA set a target of 36 States reaching the demonstration stage (defined as testing and piloting the innovation) or better using data-driven safety analysis by September 30, 2016. As of late 2016, 37 States had reached that stage. As of November 2016, the Office of Safety provided data-driven safety analysis support to 41States, resulting in the delivery of 7 peer exchanges and 125 training and technical assistance sessions. FHWA’s efforts resulted in 19 States developing policies and procedures related to data-driven safety analysis and 29 States developing action or implementation plans for integrating safety performance into all highway investment decisions.
A systematic safety analysis can help planners determine where to implement safety measures. These images illustrate some of the factors in addition to crash history that an agency may consider in identifying and prioritizing locations to install cable median barriers, such as horizontal curves (left), entrance and exit ramps (center), median width (right), and high traffic volume.
“So far, 42 States have employed data-driving safety analysis to identify and properly scope projects, evaluate alternatives, select design criteria, and monitor system performance,” says Jerry Roche, a safety engineer in the FHWA Office of Safety. “Under EDC-4, we hope to institutionalize data-driven safety analysis in State procedures, as well as increase usage by local agencies.”
By advocating for broader deployment of predictive and systemic analysis approaches to decisionmaking on investments in highway safety, the EDC focus on data-driven safety assessment seeks to improve on traditional approaches that rely on crash history data at a given site and prioritizing hot-spot fixes. The net result is a more scientifically sound, data-driven approach to allocating resources--and, ultimately, fewer and less severe crashes.
The EDC-3 initiative focused largely on reaching out to State DOT personnel. Under EDC-4, this initiative will expand its emphasis to local agencies. The development of local road safety plans to identify and prioritize the funding of low-cost safety improvements has proven to be a highly successful strategy to implement the systemic approach and will be added to the activities promoted under data-driven safety analysis. Local road safety plans result in greater safety awareness among local agencies and greater participation in their State’s Strategic Highway Safety Plan and Highway Safety Improvement Program. The EDC-4 effort will build on work accomplished under EDC-3 to ensure that safety planning at the State and local levels is data driven and efficiently addresses safety on all public roads.
FHWA’s EDC initiative has sparked greater use of innovative technologies and processes within the U.S. transportation industry. In the area of safety, the focus on implementing SafetyEdge, high-friction surface treatments, intersection and interchange geometrics, road diets, and data-driven safety analysis has saved many lives.
“The long-term goal of EDC is to integrate these innovative technologies or processes into the standards, specifications, and manuals that highway professionals use every day, and, more broadly, to demonstrate the value of continually seeking new and innovative ways for the transportation industry to work better, smarter, and faster,” says Tony Furst, FHWA’s Chief Innovation Officer.
Legislators recognized the positive results from the EDC program in the Fixing America’s Surface Transportation (FAST) Act, signed on December 4, 2015. As part of this law, Congress directed FHWA to continue the EDC program, identifying and promoting a new collection of market-ready innovations and best practices at least every 2 years. With four rounds and counting, the EDC initiative will continue to foster and promote safety innovations that improve the Nation’s roadways for all users.
Michael S. Griffith is the director of the Office of Safety Technologies and has worked for the U.S. Department of Transportation for 27 years. He has a B.S. in business management from Ithaca College, an M.A. in statistics from SUNY University at Buffalo, and an M.S. in transportation engineering from the University of Maryland.
Joseph Cheung is a civil engineer in FHWA’s Office of Safety. He has both a B.S. and an M.S. from the University of Maryland and is a registered professional engineer in the State of Maryland. He is currently serving on the Transportation Research Board’s Committee on Roadside Safety Design and Committee on Visibility.
Cathy Satterfield is a safety engineer in FHWA’s Office of Safety focusing on reducing roadway departures and improving visibility. She holds a B.S. in civil engineering from the University of Minnesota and a professional engineer’s license in Idaho.
Jeffrey Shaw is a safety engineer with the FHWA Office of Safety. He holds a B.S. in civil engineering from the Illinois Institute of Technology and is a licensed professional engineer in Illinois.
For more information, visit www.fhwa.dot.gov/innovation/everydaycounts or contact Michael Griffith at 202–366–9469 or email@example.com.