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Public Roads - May/June 2013

May/June 2013
Issue No:
Vol. 76 No. 6
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates

by Lisa Jackson of FHWA's Office of Corporate Research, Technology, and Innovation Management

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 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
5301 Shawnee Road
Alexandria, VA 22312
Telephone: 703–605–6000
Toll-free number: 1–888–584–8332
Web site:

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
Telephone: 814–239–1160
Fax: 814–239–2156

For more information on R&T communications products available from FHWA, visit FHWA's Web site at (or email, or the National Transportation Library at (or email

Performance Testing for Superpave and Structural Validation (Report)

Publication Number: FHWA-HRT-11-045

Cover of the report, Performance Testing for Superpave and Structural Validation.This report shares findings from research conducted under two transportation pooled fund projects: Full-Scale Accelerated Performance Testing for Superpave and Structural Validation and Accelerated Pavement Testing of Crumb Rubber Modified Asphalt Pavements. Researchers identified specification tests that perform better than current SUperior PERforming Asphalt PAVEment (Superpave®) tests at determining expected fatigue cracking and rutting performance. Full-scale accelerated pavement testing and laboratory characterization tests on mixtures and binders provided the basis for recommendations.

The researchers evaluated the tests based on their ability to discern resistance to fatigue cracking and rutting. Using full-scale performance and laboratory tests, the researchers demonstrated that asphalt modified with crumb rubber could significantly slow or stop the growth of fatigue cracks in a composite asphalt pavement structure. A hybrid technique to modify asphalt with a combination of crumb rubber and conventional polymers, called terminally blended crumb rubber, exhibited good fatigue cracking resistance relative to the control binder. Also, the simple addition of polyester fibers to asphalt mix provided high resistance to fatigue cracking without the use of polymer modification.

The researchers also quantified the capabilities of the National Cooperative Highway Research Program's methodologies for mechanistic-empirical pavement design and analysis to predict rutting and fatigue cracking of modified asphalts.

The report is available to download at Printed copies are available from the PDC.

Federal Highway Administration 100-Year Coating Study (TechBrief)

Publication Number: FHWA-HRT-12-045

Cover of the TechBrief, Federal Highway Administration 100-Year Coating Study.This TechBrief, which summarizes the report Federal Highway Administration 100-Year Coating Study (FHWA-HRT-12-044), presents the results and major findings from a performance evaluation of eight selected coating systems based on experimental data from laboratory and field testing.

The study began in August 2009 and focused on searching for durable coating systems with the potential to provide 100 years of virtually maintenance-free service life for steel bridge structures at costs comparable to existing coatings. Researchers selected three three-coat systems (two of which served as controls for the study), four two-coat systems, and one single-coat system of high-ratio calcium sulfonate alkyd. Then they evaluated all the coating systems under accelerated laboratory testing as well as outdoor exposure under natural weathering with and without salt spray in McLean, VA, and at the Golden Gate Bridge in San Francisco, CA.

The study found that none of the selected coating systems, including the two three-coat control systems, will provide maintenance-free corrosion protection for 100 years. Based on performance records in earlier FHWA studies, the researchers had selected two three-coat control systems that performed better than other test coating systems in every category. They selected five test coating systems hypothesized to provide superior performance compared to commercially available products, but these did not deliver desirable performance exceeding the three best coating systems. Further, the researchers observed unexpected premature failure of two of the two-coat systems. Three of the tested coating systems performed satisfactorily in some categories but poorly in others compared to the best performers.

This TechBrief is available to download at Printed copies are available from the PDC.

Casual Carpooling Scan Report (Report)

Publication Number: FHWA-HRT-12-053

Cover of the Casual Carpooling Scan Report.This report discusses the results of a study on casual carpooling, also known as dynamic ridesharing, conducted for FHWA's Exploratory Advanced Research (EAR) Program. The study involved a scan team of transportation professionals, academics, and entrepreneurs who visited informal carpool lines (also known as slug lines or casual carpool lines) in San Francisco, CA; Washington, DC; and Houston, TX, in November and December 2010.

The team observed "slugs" (riders who typically assemble at bus stops and park-and-ride lots throughout a metro area to catch a ride to work) and compared practices among locations. They also met with private ride-match providers, regional planners, carpool participants, and transportation planners and engineers. Scan team members reported on what they learned at the casual carpooling sites and identified gaps in the data and research.

The team found that casual carpooling participants are motivated by saving time and money. Passengers tend to feel safer when there is a second occupant in the vehicle, but a second passenger is not always required for passengers to feel safe getting into a car. Infrastructure, including barrier-separated reversible high-occupancy vehicle (HOV) lanes, park-and-ride lots, and direct access to HOV lanes from parking areas, can play an important role in creating conditions conducive to casual carpooling. Transit and casual carpooling are complementary modes of transportation, as slugs tend to use transit as a backup mode. The team also noted that it is difficult to say what role technology might play in bringing casual carpooling to new locations.

This report is available to download at Appendix B to the Casual Carpooling Scan Report (FHWA-HRT-13-023), which includes the observations of the individual members of the scan team at each slug line, is available to download at