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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - November/December 2014

November/December 2014
Issue No:
Vol. 78 No. 3
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates

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 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, the FHWA Research Library at (or email, or the National Transportation Library at (or email

State of the Practice and Art for Structural Health Monitoring of Bridge Substructures Publication Number:

dep11Based on standards established by the Florida Department of Transportation and FHWA, visual inspections of U.S. bridges are required every 2 years. And although visual inspections are adequate, they do not provide a reliable way to determine the actual health of a bridge’s foundation elements. This report offers an overview of the benefits of remote data acquisition systems for the short- and long-term monitoring of highway bridges. It also includes a discussion of previous methods for monitoring foundation health for comparison throughout the life cycle of the bridge.

Researchers used wireless communication and Internet systems technologies to provide remote monitoring capabilities for structural members. A voided shaft test site in Clearwater, FL, and a bridge replacement site in Minneapolis, MN, served as the primary proving grounds. Researchers obtained data from beneath the ground to assess health and performance, and to review capabilities of a low-cost automated data acquisition system. They evaluated the system by remotely uploading information to a host server and making spontaneous changes to the system configuration without a site visit.

The study provides an overview of procedures for remote automated monitoring that bridge owners can apply to a structural element to enable lifetime monitoring. These techniques include a variety of sensors and devices to record temperature, load, strain, movement, and other vital parameters to monitor structural health.

The study highlights the convenience and, in some instances, limitations and considerations when planning a remote monitoring program. It summarizes the successes and learning experiences gained from this project, including a review of the short- and long-term monitoring procedures implemented on the I–35W Bridge in Minneapolis, MN. Researchers explain the construction, setup, instrumentation, monitoring procedure, and results for a full-scale remote structural health monitoring system.

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

An FHWA Special Study: Post-Tensioning Tendon Grout Chloride Thresholds
Publication Number: FHWA-HRT-14-039

dep12Elevated levels of chloride were recently found in a commercially pre-bagged grout powder for grouting tendons in post-tensioned bridges. The chloride value in the powders exceeded the current limits set by all of the domestic and international regulatory committees.

A chloride threshold is defined as the minimum chloride concentration needed to induce corrosion. However, there is limited information pertaining to the actual chloride threshold for seven-wire prestressed strands. Prompted by the high chloride levels found in the commercial powders, FHWA conducted a 6-month accelerated corrosion testing program to determine chloride thresholds for post-tensioned strands.

This report discusses the testing program and presents two chloride threshold values determined for post-tensioned strands that were fully encased in the contaminated grout. The first threshold value has a 0.4 percent chloride concentration by weight of cement, which is the lowest amount to initiate corrosion of the strands. At this threshold, researchers demonstrated that rust spots can form and a small number of pits can start to form beneath some of those spots. The second chloride threshold is 0.8 percent chloride concentration by weight of cement for corrosion propagation. At this threshold, researchers determined that corrosion starts to intensify in terms of the number of pits and pit depth; this threshold is considered critical.

Once a chloride concentration exceeds the critical threshold, significant corrosion damage can be anticipated, and the long-term structural integrity of the bridge may be compromised. If post-tensioned tendons contain carbonated grout, segregated grout, cracks in the duct, voids filled with water with or without chloride ions, or free sulfate ions in contact with the strands, corrosion is possible below the proposed threshold values.

This report is available at Printed copies are available from the PDC.

Efficient and Safe Merging Solutions--Advanced Freeway Merge Assistance: Harnessing The Potential of Connected Vehicles
Publication Number: FHWA-HRT-14-045

dep13Freeway merging, a major safety concern, can cause traffic to slow and contribute to bottlenecks and crashes. This fact sheet discusses an Exploratory Advanced Research (EAR) Program project designed to improve the efficiency and safety of freeway merges using connected vehicle technology.

The project, Advanced Freeway Merge Assistance: Harnessing the Potential of Connected Vehicles, focused on developing and evaluating freeway merge assistance systems that may significantly improve operations in a connected vehicle environment.

As a starting point, the Center for Transportation Studies at the University of Virginia conducted a study in 2008 that developed strategic algorithms for improving merging. Researchers developed a dynamic lane control algorithm to encourage lateral movements of mainline vehicles by using a lower speed limit for the far right lane of the freeway; a gap-responsive onramp signal algorithm to give a ramp vehicle the green light based on expected gap availability in the freeway mainline; and a merging control algorithm to control and advise speed changes for mainline and ramp vehicles to enable safe merging in the smallest space, at the highest speed possible.

Researchers on the EAR project aimed to enhance the efficiency and safety of these algorithms. Leveraging the communications capabilities of connected-vehicle technologies, the researchers integrated microscopic traffic simulations with wireless network simulations. The blended simulation results helped in designing and assessing traffic impacts of control actions associated with freeway merging. To determine the safety impacts of various scenarios, the researchers developed a safety evaluation module to project the number of crashes.

This research has the potential to significantly improve freeway merge operations. Additional research is recommended to further develop the concept of operations, understand its value, and identify promising deployment scenarios.

The document is available at Printed copies are available from the PDC.

Guidelines for the Implementation of Reduced Lighting on Roadways
Publication Number: FHWA-HRT-14-050

dep14Streets and roads may be illuminated with more light than is necessary or lighting may be maintained too conservatively. The energy required for roadway lighting is considerable and can comprise a significant portion of a transportation agency’s budget. The goal of adaptive lighting is to provide an acceptable degree of illumination for the safety of roadway users while minimizing costs.

The guidelines presented in this report address the need to maintain the safety effects of roadway lighting while alleviating the budgetary strains associated with the maintenance and operation of the lighting infrastructure. The report proposes a new set of criteria for practitioners to apply to their roadway environments. The criteria identify appropriate lighting levels for given roadway characteristics and usage.

The methodology for applying the criteria is based on existing international standards that accommodate various roadway characteristics and usage. The criteria presented in the report use real-world lighting data and robust statistical analysis of the crash histories of associated roadways. Practitioners are likely to benefit from the enhanced data collection and statistical approaches.

For an adaptive lighting solution to produce a financial benefit, it should include a control system that is either central or localized on each luminaire, a dimmable-controls-ready luminaire, and a localized metering or negotiated adaptive lighting electricity rate. The control system, the primary component of the adaptive lighting methodology, should be monitored and managed from a central location.

Primary benefits of adaptive lighting include lower energy use (potentially a 20- to 40-percent reduction), reduced maintenance, fewer traffic interruptions caused by maintenance, less light pollution, and reduced roadway glare, all while maintaining roadway safety.

This document is available at Printed copies are available at the PDC.