Below are brief descriptions of communications products recently developed by the Federal Highway Administration's 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 website 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
5301 Shawnee Road
Alexandria, VA 22312
Telephone: 703–605–6050
Toll-free number: 1–888–584–8332
Website: www.ntis.gov
Email: customerservice@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
700 North 3rd Avenue
Altoona, PA 16601
Telephone: 814–239–1160
Fax: 814–239–2156
Email: report.center@dot.gov

For more information on R&T communications products available from FHWA, visit FHWA's website at www.fhwa.dot.gov, the FHWA Research Library at https://highways.dot.gov/research/resources/research-library/federal-highway-administration-research-library (or email fhwalibrary@dot.gov), or the National Transportation Library at ntl.bts.gov (or email library@dot.gov).

Properties and Behavior of UHPC-Class Materials

Publication Number: FHWA-HRT-18-036

Ultra-high performance concrete (UHPC) is a cementitious composite material composed of an optimized gradation of granular constituents, a water-to-cementitious materials ratio less than 0.25, and a high percentage of discontinuous internal fiber reinforcement. UHPC-class materials can be differentiated from conventional concrete-like materials by their exceptional mechanical and durability properties. As the demand for this innovative class of materials increases, so will the need for knowledge about the material properties and characteristics.

To fill this knowledge gap, researchers at FHWA's Turner-Fairbank Highway Research Center (TFHRC) executed an experimental study on six different commercially available materials being marketed as UHPC class. The goal of the research was to provide the bridge engineering community with a more comprehensive set of properties for this class of materials, which in turn could facilitate broader use within the sector. The researchers evaluated the UHPC-class materials using 14 different test methods developed by ASTM, the American Association of State Highway and Transportation Officials, or the TFHRC. Results indicate that these materials behave similarly with respect to some performance measures such as compressive strength, tensile strength, and durability, but vary with respect to others such as dimensional stability, bond to precast concrete, and compressive creep.

The publication is available at www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/18036/index.cfm.

Performance of Grouted Connections for Prefabricated Bridge Deck Elements

Publication Number: FHWA-HIF-19-003

Accelerated bridge construction (ABC) has become increasingly popular for new bridges and for replacement/rehabilitation projects. ABC offers numerous advantages, which include reduced traffic disruption, expedited project delivery, and increased work zone safety. To realize some of these advantages, construction typically employs prefabricated bridge elements and systems (PBES).

Laboratory research and field studies indicate that the primary challenge for PBES lies in the design and construction of the connections, which are typically made using interlaced connector elements and field-cast grout. Poor detailing and design considerations have been shown to pose problems with fabrications, construction, durability, and capacity.

This study investigated deck-level connections employing interlaced reinforcing bars with different grout materials and different precast panel details for potential use in accelerated bridge construction projects. The research team began by reviewing relevant literature to determine promising grout materials for field-cast connections as well as different precast panel details currently being deployed in precast deck systems. Researchers then created a test matrix of grout materials and different connection detail combinations.

The research team conducted two series of experiments. The first tested the bond behavior between precast concrete and different connection grouts. The second investigated several parameters frequently considered during the design of these connections: shear key shape, reinforcement type, connection grout material type, and precast surface preparation.

The study concluded that test variables showed varying influence on the behavior of the deck-level connections. Thus, the selection of field-cast grout materials represents one of the most critical design considerations for deck-level PBES connections.

The publication is available at www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/19003/index.cfm.

Techbrief: Safety Evaluation of Flashing Yellow Arrows at Signalized Intersections

Publication Number: FHWA-HRT-19-035

A flashing yellow arrow for permissive left-turn movements at signalized intersections helps drivers who are turning left on a permissive circular green signal avoid confusion. The concern is that drivers turning left on a permissive circular green signal might mistake that signal as implying that the left turn has the right-of-way over opposing traffic, especially under certain geometric conditions.

FHWA's study aimed to undertake a before-and-after evaluation of the safety effectiveness of flashing yellow arrows at signalized intersections. The study used data from four States—Nevada, North Carolina, Oklahoma, and Oregon—to examine the effects for specific crash types, including total, injury and fatal, rear-end, angle, left-turn, and left-turn opposite through crashes. The evaluation included 307 treated sites and 438 reference sites.

The research found that a flashing yellow arrow is the best overall alternative to the circular green signal as the permissive signal display for a left-turn movement and that left-turn drivers demonstrated a high level of understanding and correct response to flashing yellow arrows. Also, a flashing yellow arrow display in a separate signal face for the left-turn movement offers more versatility in field application. It is capable of operating in any of the various modes of left-turn time-of-day operations and is easy to program to avoid the "yellow trap" associated with some permissive turns at the end of the circular green signal.

The results of this study show that crashes decrease when flashing yellow arrow signal phasing replaces a permissive or protected/permitted left-turn signal. The crash reduction ranged from 15 to 50 percent depending on the treatment type. The treatment has a positive benefit, especially for total crashes, injury and fatal crashes, and crashes related to left-turn movements.

The publication is available at www.fhwa.dot.gov/publications/research/safety/19035/index.cfm.

Asphalt Binder and Mixture Laboratory (ABML) Look-In

Publication Number: FHWA-HRT-20-057

The Asphalt Binder and Mixture Laboratory–Implementation and Delivery (ABML-ID) is currently assessing automated asphalt extraction technology prescribed in ASTM D8159, the Standard Test Method for Automated Extraction of Asphalt Binder from Asphalt Mixtures. Evaluations will be based on the comparison of physical property changes in high, intermediate, and low-temperature asphalt binders, reclaimed asphalt pavement (RAP), and binder blended with RAP extracted using the traditional AASHTO T 164 Method A and automated extraction.

ASTM D8159 covers the quantitative determination of asphalt binder content in asphalt mixtures and pavement specimens—using the automated computer controller or human-machine interface system—to perform a solvent extraction for specification acceptance, service evaluation, quality control, and research. The benefits of ASTM D8159 include the reduction of sources of variability due to automated process, ease of use, less hazardous material exposure, reduction in purchase and disposal costs of trichloroethylene, and determination of asphalt binder content and gradation in one working day.

ABML-ID is a partnership between the Office of Preconstruction, Construction, and Pavements; the Office of Infrastructure Research and Development; and the Resource Center to actively support implementation-focused activities that advance research products into field evaluation and deployment. The ABML-ID supports the FHWA Mobile Asphalt Technology Center in providing technical expertise to the asphalt pavement community. ABML-ID also focuses on projects of national interest from State departments of transportation and stakeholders.

The publication is available at www.fhwa.dot.gov/publications/research/infrastructure/pavements/20057/index.cfm.

High Friction Surface Treatment (HFST) Quick Reference

High Friction Surface Treatment (HFST) is a pavement surface treatment consisting of a polymer resin binder used to bond a 1- to 3-millimeter nominal-size polish- and abrasion-resistant aggregate to the pavement surface. HFST is typically used as a spot treatment on targeted locations, and specifically restores or enhances the friction of virtually any structurally sound pavement surface to reduce roadway departure crashes.

This quick reference guide provides an overview of HFST including applications, site selection, specifications, materials, installation, inspection, testing and acceptance, and performance monitoring. It also provides links to additional resources for more information.

The publication is available at www.fhwa.dot.gov/publications/research/safety/highfriction/index.cfm.