U.S. Department of Transportation
Federal Highway Administration
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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-12-003 Date: March/April 2012|
Publication Number: FHWA-HRT-12-003
Issue No: Vol. 75 No. 5
Date: March/April 2012
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:
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/research/library (or email firstname.lastname@example.org), or the National Transportation Library at ntl.bts.gov (or email email@example.com).
Publication Number: FHWA-HRT-11-041
On February 23, 2011, leaders from the FHWA Office of Operations Research and Development and the Exploratory Advanced Research Program convened a 1-day workshop to examine technological innovations in accessible transportation and better understand the needs of pedestrians and travelers with visual impairments or other disabilities. A panel of speakers consisting of disability experts, academics, transportation industry experts, and other professionals gathered at the Turner-Fairbank Highway Research Center in McLean, VA, to discuss applications of technology, identify knowledge gaps and opportunities, and highlight barriers to implementation.
The report includes the six presentations from the workshop on topics ranging from economics, situational environmental awareness, and accessibility to intelligent transportation systems, robotics, wayfinding, and mobile technology. Workshop attendees participated in four group discussions, and the report includes summaries and recommendations from each group on subjects that include intelligent transportation systems, wireless technologies, and mobile computing; robotics, artificial intelligence, and object detection; navigation, wayfinding, orientation, and guidance; and universal design and accessible transportation. Workshop participants also discussed the need for research and potential next steps in simulation, improving confidence, driver assistance technology, and performance metrics.
This report is available at www.fhwa.dot.gov/advancedresearch/pubs/11041/index.cfm. An executive summary (FHWA-HRT-11-042) is also available at www.fhwa.dot.gov/advancedresearch/pubs/11042/index.cfm. Printed copies of the report and executive summary are available from the PDC.
Publication Number: FHWA-HRT-11-049
Treatments applied to pavements can delay or mitigate existing wear and tear, improving pavement performance and prolonging pavement life rather than increasing structural capacity. Effective preventive maintenance relies on selecting the appropriate technique and the timing of treatment application. This TechBrief covers experimental design, a performance indicator, statistical analysis, and results, including preferred treatments for distresses such as fatigue cracking, rutting, and roughness.
Researchers conducted a Long-Term Pavement Performance (LTTP) Specific Pavement Study SPS-3 experiment using thin hot-mix asphalt (HMA) overlay, slurry seal, crack seal, and chip seal. Each site was categorized according to moisture (wet or dry climate), temperature (freeze or no-freeze zone), subgrade type (fine grained or coarse grained), traffic load (low or high), and existing pavement condition (good, fair, or poor).
Researchers found that a thin overlay and chip seal was more effective than slurry seal and crack seal treatments and performed better than the control section for fatigue cracking. The thin overlay mitigated and slowed the progression of rutting under all circumstances, and there were no significant differences between slurry seal, crack seal, and the control with respect to rutting. Chip seal effectively reduced the development of rutting in no-freeze zones and wet regions; only the thin overlay was effective in mitigating and delaying the progression of roughness under certain conditions. For any existing level of rutting, thin overlays outperformed the other treatments followed by chip seals; thin overlays and chip seals outperformed other treatments when the existing section had minimal cracking prior to the treatment and higher levels of preexisting cracking. Maintenance costs are a critical factor when deciding which mixture type to use.
This report is available at www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/11049/index.cfm. Printed copies are available from the PDC.
Publication Number: FHWA-HRT-11-050
This TechBrief compares the performance of rehabilitation strategies for flexible and rigid pavements. Researchers evaluated statistically the impacts of overlay thickness, preparation prior to overlay, and mix type on performance using data from LTPP SPS-5 and SPS-6 experiments.
Techniques commonly used in the United States and Canada were applied to test sections on a continuous highway site, which guaranteed all sections were subjected to the same climate conditions and traffic and were constructed under the same subgrade and pavement structure. The factors considered in the experiment included the type of treatment, surface condition before completion of rehabilitation, environmental conditions, and traffic load. Thirty-two sites built for SPS-5 and SPS-6 included 18 rehabilitation projects over flexible pavements, 8 asphalt concrete over joint plain concrete pavements (JPCP), and 6 over joint reinforced concrete pavements (JRCP). The researchers monitored the sites for periods ranging from 8 to 17 years.
They found that thick overlays improved the performance of rehabilitated flexible pavements for smoothness and fatigue cracking. Mix type did not have a statistically significant effect on performance. Milling the existing HMA surface prior to overlay was effective in keeping the overlay smooth, and smoothness performance was improved significantly in all JPCP and JRCP sections overlaid with HMA, with thicker HMA overlays producing smoother pavements. In comparison, rehabilitation strategies applied to rigid pavements without HMA overlays did not exhibit as smooth surfaces. The maximum preparation showed improved smoothness over minimum preparation for JPCP, but not for JRCP.
The report is available at www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/11050/index.cfm. Printed copies are available from the PDC.
Publication Number: FHWA-HRT-11-051
When designed properly, reclaimed asphalt pavement (RAP) mixes have demonstrated a quality comparable to virgin HMAs. However, despite the success rate of RAP-mix projects, the perception that recycled materials are of inferior quality still persists. This TechBrief provides a summary of results from the statistical analysis of data collected during the LTPP program comparing the performance of recycled HMA to virgin mix in flexible pavement overlays.
To compare design methodologies and construction alternatives for rehabilitation of flexible pavements, researchers applied techniques commonly used in the United States and Canada to test sites in various geographical locations. Test sections at each site were subject to similar climatic, subgrade, pavement structure, and traffic conditions. Experimental factors included the surface condition prior to overlay, environment, and traffic load, as well as different treatment alternatives. Virgin and RAP mixes were used in combination with surface preparation and overlay thickness in 9 sections, including a control section, in each of the 18 sites selected for the experiment.
Results showed that RAP and virgin HMA mixes used in overlays of flexible pavements performed equivalently across a range of climates, traffic loadings, and existing pavement conditions during a period of up to 17 years.
The TechBrief is available at www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/11051/index.cfm. Printed copies are available from the PDC.
Publication Number: FHWA-HRT-11-059
Epoxy-coated reinforcement (ECR) is the principal concrete reinforcing material currently in use in corrosive environments in the United States. This TechBrief highlights a study focused on evaluating methods for making ECR more corrosion resistant by using multiple corrosion-protection strategies in bridge decks and components in marine environments where salt, moisture, and high temperatures are prevalent.
Researchers used laboratory and large field test specimens and compared the performance of corrosion-protection systems on the basis of chloride threshold, corrosion rate, life expectancy, and cost effectiveness. They evaluated fusion-bonded thermoset ECR in conjunction with inorganic and organic corrosion inhibitors, bars coated with zinc prior to the application of epoxy, and chemical pretreatments and epoxy formulations that increase the adhesion of the epoxy coating to reinforcing steel.
Researchers analyzed 11 systems in which ECR was combined with another corrosion-protection system and 3 systems in which uncoated steel was combined with a corrosion inhibitor. The researchers determined that conventional fusion-bonded epoxy coatings significantly improve the corrosion resistance, life expectancy, and cost effectiveness of reinforcing steel in severe climates. Coated bars with damaged coatings initiate corrosion at chloride contents within concrete that are several times greater and corrode at rates that are typically two orders of magnitude below those exhibited by conventional reinforcement.
Research findings on conventional reinforcement, cracks, epoxies, reduced water-cement ratio, corrosion inhibitors, reinforcement with multiple coatings, coated bars, and adhesion reductions also are discussed in this TechBrief, which is available at www.fhwa.dot.gov/publications/research/infrastructure/bridge/11059/index.cfm. Printed copies are available from the PDC.