U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590
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-10-005 Date: July/August 2010|
Publication Number: FHWA-HRT-10-005
Issue No: Vol. 74 No. 1
Date: July/August 2010
Below are brief descriptions of communications products recently developed by the Federal Highway Administration's (FHWA) Office of Research, Development, and Technology. All of the reports are or will soon be available from the National Technical Information Service (NTIS). In some cases, limited copies of the communications products are available from FHWA's Research and Technology (R&T) Product Distribution Center (PDC).
When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at www.ntis.gov to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Toll-free number: 800-553-NTIS (6847)
Web site: www.ntis.gov
Requests for items available from the R&T Product Distribution Center should be addressed to:
R&T Product Distribution Center
Szanca Solutions/FHWA PDC
13710 Dunnings Highway
Claysburg, PA 16625
For more information on R&T communications products available from FHWA, visit FHWA's Web site at www.fhwa.dot.gov, the Turner-Fairbank Highway Research Center's Web site at www.tfhrc.gov, the National Transportation Library's Web site at http://ntl.bts.gov, or the OneDOT information network at http://dotlibrary.dot.gov.
Development of a Multiaxial Viscoelastoplastic Continuum Damage Model for Asphalt Mixtures
Publication No. FHWA-HRT-08-073
Mathematical Analysis of the Empirical Mode Decomposition is a 3-year study sponsored by the FHWA Exploratory Advanced Research Program and awarded to Princeton University to develop a mathematical foundation for empirical mode decomposition (EMD). Invented more than 10 years ago, EMD provides a nonlinear time-frequency analysis with the ability to evaluate nonstationary signals. Transportation-related applications of EMD could include detecting early signs of fatigue in vibrating metal components and locating cracks or loss of rigidity in reinforced bridge columns. This fact sheet discusses EMD's origins, mathematical challenges, and potential benefits to the transportation industry.
Over the past decade, researchers have developed uniaxial material models that can accurately capture various critical phenomena such as microcrack-induced damage that is critical in fatigue modeling, strain-rate temperature interdependence, and viscoplastic flow. The initial model focused on uniaxial tension behavior; however, accurately predicting the performance of an asphalt mixture in a pavement structure requires a multidimensional model. The multiaxial viscoelastoplastic continuum damage model combines elements of viscoelasticity, continuum damage mechanics, and viscoplasticity to model the material's behavior. Another factor critical to predicting the performance of the real pavement structures is incorporating the material model into a pavement model that considers the vehicle and climatic loads and the boundary conditions. Researchers developed the in-house finite element package for this purpose. According to the report's conclusions, the resulting predictions are reasonable and a reliable simulation of pavement response. Researchers are now applying these models within a performance specification for asphalt mixtures.
The report is available at www.fhwa.dot.gov/publications/research/infrastructure/pavements/08073/index.cfm. Printed copies also are available from the PDC.
Real-Time Pedestrian Detection: Layered Object Recognition System for Pedestrian Collision Sensing (Fact Sheet)
Publication No. FHWA-HRT-10-022
Current pedestrian detection technologies use fixed cameras pointing at predetermined zones, or vehicle-mounted monocular camera systems. To detect pedestrians more accurately and reduce pedestrian fatalities, a project spon-sored by FHWA's Exploratory Advanced Research (EAR) Program moves beyond current systems and integrates two- and three-dimensional technology to provide cues for potential locations of pedestrians. This fact sheet dis-cusses the current state of the technology, the project's layered processing framework, the major challenges to overcome, and future efforts.
This EAR project focuses on developing a real-time, in-vehicle, vision-only system to detect pedestrians and to determine potential collisions with high accuracy and minimal false alarms. Using multiobject classification, the system distinguishes seven classes of objects—the ground, pedestrians, vehicles, buildings, bushes, trees, and other tall vertical structures such as light poles. The layered pedestrian-detection algorithm can then recognize objects that are not pedestrians and eliminate them from analysis, gaining real-time performance speed in hazard identification.
The fact sheet is available at www.fhwa.dot.gov/advancedresearch/pubs/10022/index.cfm. Printed copies are available from the PDC.
Driving Automation Forward: Human Factors For Limited-Ability Autonomous Driving Systems (Fact Sheet)
Publication No. FHWA-HRT-10-021
In May 2010, speaking to students and faculty at the Massachusetts Institute of Technology, Secretary of Transportation Ray LaHood underscored the need to enlist the country's best and brightest to help solve today's transportation challenges. Among those challenges are designing vehicles that emit zero greenhouse gases, engineering a revolution in green energy, and building cars that do not crash. On the latter point, FHWA's Human Factors for Limited-Ability Autonomous Driving Systems, an EAR project, aims to investigate driver engagement through the development of limited-ability autonomous driving systems. This fact sheet discusses a brief history of vehicle automation, knowledge gaps in working with human factors, automated driving challenges, and the future of automation.
The EAR project addresses a critical technology and knowledge gap that limits the near-term availability of vehicles that can control their own speeds and steering for substantial distances on public roads. One question is how to help drivers maintain adequate situational awareness so they are prepared to intervene when traffic conditions require. With this in mind, the EAR project will use smart adaptive cruise control, lane centering, and two next-generation driver-assistance technologies that automate longitudinal and lateral control. The study will involve human factor studies and experiments in simulators, on test tracks, and on public roads.
The fact sheet is available at www.fhwa.dot.gov/advancedresearch/pubs/10021/index.cfm. Printed copies are available from the PDC.
High Performance Concrete Bridge Deck Investigation (TechBrief)
Publication No. FHWA-HRT-09-070
As part of an FHWA technology deployment initiative begun in 1993, State transportation departments started using high performance concrete (HPC) in their bridges. The program included the construction of demonstration bridges throughout the United States, which provided researchers with a large amount of data on the use of HPC. This re-port provides a summary of the performance of those bridges and information on the program's objective, background, investigation process, results, and recommendations.
FHWA compiled information from the demonstration bridges and used that data to develop recommendations on basic design parameters for HPC. The data included photographs and cross-sectional drawings of the bridges, as well as details about the materials and methods used in construction. The investigation demonstrated that HPC bridge decks can be constructed to perform well, and they exhibit relatively few cracks after multiple years of service.
The document is available at www.fhwa.dot.gov/publications/research/infrastructure/structures/09070/index.cfm. Printed copies are available from the PDC.
Structural Behavior of a 2nd Generation UHPC Pi-Girder (TechBrief)
Publication No. FHWA-HRT-09-069
Compared to more conventional concrete materials, ultra-high performance concrete (UHPC) exhibits superior properties such as exceptional durability, high compressive strength, usable tensile strength, and long-term stability. FHWA completed an experimental investigation focused on the structural behavior of a newly developed highway bridge girder cross section, the pi-girder. This girder was developed and optimized to exploit the advanced mechanical and durability properties of UHPC. The report provides information on the study's objective, the second-generation UHPC pi-girder, the test program, conclusions, initial pi-girder deployment, and recommendations for further development of the pi-girder.
The testing completed for this study focused on the structural performance of the girder's deck when subjected to simulated wheel loads. The design, fabrication, and testing of a second-generation UHPC pi-girder modular bridge component demonstrated the viability of the decked UHPC modular girders concept for use in conventional and accelerated bridge construction. The researchers found that the transverse flexural capacity of the girder is sufficient, and the capacity of the longitudinal joint exceeded that of the prefabricated deck.
The document is available at www.fhwa.dot.gov/publications/research/infrastructure/structures/09069/index.cfm. Printed copies are available from the PDC.
Structural Behavior of a Prototype UHPC Pi-Girder (TechBrief)
Publication No. FHWA-HRT-09-068
FHWA conducted an experimental investigation focused on the structural behavior of a newly developed highway bridge girder cross section, the pi-girder. This girder was developed and optimized to exploit the advanced mechanical and durability properties of UHPC. This report provides information on the study's objective, the UHPC prototype pi-girder, the test program, conclusions, and recommendations for further development of the pi-girder.
The research program included two phases. The first phase focused on the manufacture of four UHPC pi-girders. Workers fabricated these 70-foot (21.3-meter)-long prestressed girders at a conventional production plant for precast bridge girders and then transported them to FHWA's Turner-Fairbank Highway Research Center. The second phase focused on the physical testing of the full-scale girders through the application of structural loads. The research demonstrated that the concept of decked UHPC modular girders for bridge construction is viable. The structural response of the girder prototype exceeds design requirements in terms of ultimate shear capacity and meets flexural design requirements with the inclusion of appropriate prestress force.
The document is available at www.fhwa.dot.gov/publications/research/infrastructure/structures/09068/index.cfm. Printed copies are available from the PDC.
Simulator Evaluation of Low-Cost Safety Improvements on Rural Two-Lane Undivided Roads: Nighttime Delineation for Curves and Traffic Calming for Small Towns (TechBrief)
Publication No. FHWA-HRT-09-062
As part of an effort to support strategic highway safety plans, FHWA organized 26 States to participate in the Evaluations of Low-Cost Safety Improvements Pooled Fund Study. The purpose of this study is to estimate the safety effectiveness of several unproven, low-cost safety strategies identified in the National Cooperative Highway Research Program Report 500 series.
This report, Simulator Evaluation of Low-Cost Safety Improvements on Rural Two-Lane Undivided Roads: Nighttime Delineation for Curves and Traffic Calming for Small Towns, examines low-cost visibility enhancements for navigating horizontal curves at night in rural areas. To help enhance the visibility of the curves, edgelines and post-mounted delineators (PMDs) were selected as the best alternatives for the simulator study. For curves, the researchers concluded that PMDs used with edgelines performed better in terms of slowing drivers down than pavement markings alone. The novel streaming PMDs solution—simulated reflectorized PMDs enhanced by light-emitting diode (LED) lamps that produce sequential streaming pattern of lights—offered the most dramatic potential benefit in terms of advanced curve detection.
Researchers also conducted tests to identify engineering measures to better manage speed on main roads through towns that are not suitable for traditional traffic calming techniques. The simulator study investigated the speed-calming effects of chicanes—artificial features that create extra turns in a roadway—located at the entrance to and exit from a town. In addition, bulbouts—curb extensions designed to slow drivers down—were evaluated at intersection locations in a town. For towns, the researchers concluded that chicanes slowed drivers the most, followed by parked cars on both sides of the road.
This document is available at www.fhwa.dot.gov/publications/research/safety/09062/index.cfm. Printed copies are available from the PDC.