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Publication Number:  FHWA-HRT-15-005    Date:  July/August 2015
Publication Number: FHWA-HRT-15-005
Issue No: Vol. 79 No. 1
Date: July/August 2015


Communication Product Updates

Compiled by AUTHOR 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 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: 703–605–6000
Toll-free number: 1–888–584–8332
Web site: 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
13710 Dunnings Highway
Claysburg, PA 16625
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 Web site at www.fhwa.dot.gov, the FHWA Research Library at www.fhwa.dot.gov/research/library (or email fhwalibrary@dot.gov), or the National Transportation Library at ntl.bts.gov (or email library@dot.gov).

Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project (Report)

Publication Number: FHWA-HRT-14-020

Cover of the report Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project.Each year, more than 10,000 people are killed in speed-related crashes. The majority of these crashes occur on roads that are not part of the interstate system. Local streets and collector roads have the highest speed-related fatality rate per vehicle mile driven. To address this issue, safety professionals must help drivers better recognize road geometries, characteristics, and conditions and adjust their speed appropriately. This report discusses the effectiveness of dynamic signs that alert drivers to changes in roadway conditions and provide drivers with recommended speeds to safely negotiate a curve.

Systems of dynamic speed feedback signs are one method to reduce vehicle speeds and, consequently, crashes on curves. These systems show promise, but they have not been fully evaluated on curves. The Center for Transportation Research and Education at Iowa State University conducted a national demonstration project to evaluate the effectiveness of two different signs in reducing speeds and crashes on curves along two-lane roadways at 22 sites in 7 States. The project aims to provide traffic safety engineers and other professionals with additional tools to more effectively manage speeds and crashes on rural horizontal curves.

Researchers collected data before and at 1, 12, and 24 months after installation of the dynamic speed feedback signs. On average, most sites had decreases in mean speeds, with decreases up to 10.9 miles (17.5 kilometers) per hour, noted at both the point of curvature and center of the curve. Researchers compared the numbers of vehicles traveling 5, 10, 15, and 20 miles (8, 16, 24, and 32 kilometers) over the posted or advisory speed limit. Large reductions in the number of vehicles traveling over the posted or advisory speed occurred for all of the after periods, indicating that the signs were effective in reducing high-end speeds, as well as average speeds.

Researchers also conducted a before-and-after crash analysis, and developed crash modification factors ranging from 0.93 to 0.95 depending on the crash type and direction of the crash.

This document is available to download at www.fhwa.dot.gov/publications/research/safety/14202/index.cfm.

Long-Term Bridge Performance High Priority Bridge Performance Issues (Report)

Publication Number: FHWA-HRT-14-052

Cover of the report Long-Term Bridge Performance High Priority Bridge Performance Issues.FHWA initiated the Long-Term Bridge Performance (LTBP) Program to collect, store, and analyze data to better understand how bridges deteriorate over time. Bridge performance includes performance of materials, protective systems, individual components of the bridge, and the structural system as a whole.

The success of the LTBP Program depends on being able to identify the most important performance issues faced by bridge owners. As a starting point, researchers classified possible issues and the parameters influencing performance into the following categories: structural condition (durability and serviceability, including fatigue); functionality (user safety and service); costs (to State departments of transportation and users); and structural integrity (safety and stability in failure modes).

Researchers sought input from bridge owners and key stakeholders. They interviewed bridge experts in 15 State DOTs and asked them to name the most common or difficult-to-solve performance issues in their bridge inventories. This report includes findings from these interviews. The research team also held a workshop to identify high priority issues related to the performance of bridge substructures.

Researchers used the findings from the interviews and workshop to develop a list of 22 high priority performance issues. From this list, they recommended six bridge performance issues as the first topics to be studied under the LTBP Program. These topics include treated and untreated concrete bridge decks, deck joints, bearings, coatings for steel bridge superstructure elements (including weathering steel), and detection of the condition of embedded pretensioned strands and post-tensioning tendons in prestressed concrete bridge sections.

This report is intended for bridge program personnel from Federal, State, and local agencies, as well as parties engaged in bridge-related research and the bridge engineering community.

This document is available to download at www.fhwa.dot.gov/publications/research/infrastructure/structures/ltbp/14052/index.cfm. Printed copies are available from the PDC.

Alkali-Silica Reaction Mechanisms and Detection: An Advanced Understanding (TechBrief)

Publication Number: FHWA-HRT-14-079

Traditional attempts to mitigate deterioration in concrete structures caused by alkali-silica reaction (ASR) focused on preventing or reducing the amount of gel formed by modifying the chemical environment. Engineers have found that limiting the alkali content of concrete, using supplementary cementitious materials, and employing chemical admixtures are effective strategies and have been used extensively for that purpose.

Given the complexity of chemical and physicalmechanisms of ASR, researchers face difficulty in developing reliable test methods for quality control and models for performance prediction. This study aimed to provide an increased understanding of the fundamental mechanisms of ASRand to develop additional options for detecting and controlling ASR in susceptible aggregates.

This document discusses detailed research methodology and several potential approaches to determine the reactivity of aggregate, mitigate ASR, and detect the damage caused by ASR. These approaches include the advanced quick chemical test, use of a model to predict the minimum dosage of lithium nitrate, use of acoustic emission, and x-ray and neutron imaging to detect damage caused by ASR.

Researchers expect that a more indepth understanding of the mechanisms underlying ASR, combined with methods to detect ASR damage developed in this study, will help to establish more reliable methods of mitigating ASR and to increase the design life of newly constructed concrete structures.

This document is available to download at www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/14079/index.cfm. Printed copies are available from the PDC.

Interlaboratory Variability of Slip Coefficient Testing for Bridge Coatings (Report)

Publication Number: FHWA-HRT-14-093

Cover of the report Interlaboratory Variability of Slip Coefficient Testing for Bridge Coatings.Bolted connections are a critical part of most steel bridges. Crews assemble individual components in the field using high-strength bolts, which are often designed to prevent slipping by relying on friction between the bolted surfaces created by the clamping force of the bolts. Because steel bridges may be painted to prevent corrosion, the coatings used on these surfaces must demonstrate a predetermined friction coefficient. The friction coefficient is defined by a test method determined by the Research Council for Structural Connections (RCSC). In recent years, the bridge engineering community--through the National Transpor-tation Product Evaluation Program of the American Association of State Highway and Transportation Officials--has noted concerns that ambiguities within the test method might increase the variability of reported friction coefficients.

This report outlines the findings and recommendations from a round-robin laboratory study on slip coefficients of organic zinc-rich primers for steel bridges. Prior to this work, coating manufacturers noted the variability of slip coefficients for the same coatings despite no changes in formulation. Researchers conducted the study to quantify the variability and recommend changes to RCSC to reduce the variability.

The researchers found that participating labs followed the RCSC procedure, but were sometimes reporting very different slip coefficients for identical coatings. The major finding was that the manner in which each lab measured slip displacement contributed to the greatest variability in frictional coefficient results.

The study recommends that RCSC clarify its intended method for measuring slip deformation. Once implemented, the team anticipates that the revised test method will appropriately quantify coating frictional coefficients and ensure proper connection performance.

This report will benefit those in charge of specifying and testing steel bridge coatings, including coating manufacturers, RCSC, State DOTs, researchers, and design consultants.

The document is available to download at www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/14093/index.cfm.




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