March/April 2008 · Vol. 71 · No. 5

March/April 2008

Communication Product Updates
Compiled by Zac Ellis of FHWA's Office of Research and Technology Services

Below are brief descriptions of products recently published online by the Federal Highway Administration's (FHWA) Office of Research, Development, and Technology. Some of the publications also may be available from the National Technical Information Service (NTIS). In some cases, limited copies are available from the Research and Technology (R&T) Product Distribution Center.

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
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-605-6000
Toll-free number: 800-553-NTIS (6847)

Address requests for items available from the R&T Product Distribution Center to:

R&T Product Distribution Center, HRTS-03
Federal Highway Administration
9701 Philadelphia Court, Unit Q
Lanham, MD 20706
Telephone: 301-577-0818
Fax: 301-577-1421

For more information on R&T publications from FHWA, visit FHWA's Web site at www.fhwa.dot.gov, the Turner-Fairbank Highway Research Center's Web site at www.tfhrc.gov, the National Transportation Library's Web site at http://ntl.bts.gov, or the OneDOT information network at http://dotlibrary.dot.gov.

Traffic Detector Handbook: Third Edition—Volume I
Publication No. FHWA-HRT-06-108

The objective of this handbook is to provide a comprehensive resource for selecting, designing, installing, and maintaining traffic sensors for signalized intersections and freeways. The handbook specifically targets audiences such as traffic engineers and technicians who work with in-roadway or over-roadway traffic sensors. These two families of sensors have different characteristics and thus corresponding advantages and disadvantages--both of which are discussed throughout the handbook. The topics covered include sensor technology, applications, in-roadway sensor design, installation techniques, and maintenance. The handbook includes the latest research available on treatments and best practices used by the surveyed jurisdictions, with references provided for students, practitioners, researchers, or decisionmakers who wish to learn more about a particular subject.

A chapter on sensor technology discusses the operation and use of inductive loop detectors, magnetic sensors and detectors, video image processors, microwave radar sensors, laser radars, passive infrared and passive acoustic array sensors, and ultrasonic sensors, plus combinations of sensor technologies. The sensor application topics address issues such as safety, operational performance, multimodal issues, and physical and economic factors. In addition, the appendixes include research, background papers, and implementation guidance.
This handbook is the first volume of the third edition and contains chapters 1 through 4. The second volume, Traffic Detector Handbook: Third Edition--Volume II (FHWA-HRT-06-139), contains chapters 5 and 6 and all appendixes.

This document is available online at www.tfhrc.gov/its/pubs/06108/index.htm. Limited copies are available from FHWA’s R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-111512.

Freeze-Thaw Resistance of Concrete With Marginal Air Content
Publication No. FHWA-HRT-06-117

Freeze-thaw resistance is a key durability factor for concrete pavements. Recommended parameters for concrete’s air void system are normally 6 ± 1 percent total air with a spacing factor less than 0.20 millimeter (0.007 inch). However, observations show that some concretes not possessing these commonly accepted thresholds still offer good freeze-thaw resistance in laboratory studies. This study evaluated the freeze-thaw resistance of several “marginal” air void mixes, with two types of air entraining admixtures: a Vinsol® resin and a synthetic admixture.

The study used rapid cycles of freezing and thawing in plain water, in the absence of deicing salts. For the specific materials and concrete mixture proportions used in this project, the marginal air mixes (concretes with fresh air contents of 3.5 percent or higher) presented  an adequate freeze-thaw performance when using the Vinsol resin-based air entraining admixture. The synthetic admixture did not show the same good performance as the resin.

The document is available online at www.fhwa.dot.gov/pavement/pccp/pubs/06117. Limited copies are available from FHWA’s R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-110357.

Pedestrian and Bicyclist Intersection Safety Indices: User Guide
Publication No. FHWA-HRT-06-130

This study developed safety indices to enable engineers, planners, and other practitioners to prioritize intersection crosswalks and approaches with respect to pedestrian and bicyclist safety. The study collected data on pedestrian and bicycle crashes, conflicts, avoidance maneuvers, and subjective ratings of intersection video clips by pedestrian and bicycle experts. A total of 68 intersection crosswalks were selected for the pedestrian analysis from the cities of Philadelphia, PA; San José, CA; and Miami-Dade County, FL. The bicycle analysis included 67 intersection approaches from Gainesville, FL; Philadelphia, PA; and Portland and Eugene, OR.

Researchers developed prioritization models based on expert safety ratings and behavioral data. The indicative variables included in the pedestrian safety index model included type of intersection control (signal or stop sign), number of through lanes, 85th percentile vehicle speed, main street traffic volume, and area type. The indicative variables in the bicycle safety models (for through, right-turn, and left-turn bike movements) included various combinations of road characteristics. These included bicycle lanes, traffic volumes on main and cross streets, the number of through lanes, presence of on street parking, main street speed limits, presence of traffic signals, and number of turn lanes.

With this user guide, practitioners will be able to use the safety indices to identify crosswalks and intersection approaches with the highest priority for in depth pedestrian and bicycle safety evaluations. Practitioners then can use other tools to address potential safety problems.

The document is available online at www.tfhrc.gov/safety/pedbike/pubs/06130/index.htm. Limited copies are available from FHWA’s R&T Product Distribution Center. The document also is available from NTIS under order number PB2008-101294.

Traffic Detector Handbook: Third Edition—Volume II
Publication No. FHWA-HRT-06-139

This handbook provides a comprehensive resource for selecting, designing, installing, and maintaining traffic sensors for signalized intersections and freeways. The target audience includes traffic engineers and technicians who are responsible for in-roadway and/or over-roadway traffic sensors. These two families of sensors have different characteristics and thus corresponding advantages and disadvantages. Topics in the handbook include sensor technology, applications, in-roadway sensor design, installation techniques, and maintenance.

The chapter on sensor technology discusses the operation and uses of inductive loop detectors, magnetic sensors and detectors, video image processors, microwave radar sensors, laser radars, passive infrared and passive acoustic array sensors, ultrasonic sensors, and combinations of sensor technologies. With regard to sensor applications, topics include safety, operational performance, multimodal issues, and physical and economic factors that practitioners should consider. The appendixes include research, background papers, and implementation guidance. The information contained in this handbook also references the latest research available on treatments and best practices in use by the surveyed jurisdictions.

This handbook is the second volume of the third edition and contains chapters 5 and 6 and all appendixes. The first volume, Traffic Detector Handbook: Third Edition—Volume I (FHWA-HRT-06-108), contains chapters 1 through 4.

The document is available online at www.tfhrc.gov/its/pubs/06139/index.htm. Limited copies are available from FHWA’s R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-111511.

Durability of Segmental Retaining Wall Blocks: Final Report
Publication No. FHWA-HRT-07-021

Segmental retaining wall (SRW) systems are commonly used in a range of applications, including highway projects. A combination of reduced construction costs, versatility, aesthetic appearance, ease of installation, and an increasing number of proprietary designs available in the market help make the system a popular choice. Despite these inherent advantages, some users have reported problems with the durability of SRW blocks in cold climates. Deterioration of some installations in State highway applications has resulted in concern over the long-term performance of SRW systems and led to stricter specifications and, in some cases, restrictions on future uses.

In response to these concerns, FHWA funded research to determine the cause and extent of SRW block distress. The study identified and recommended test methods for improving durability, and recommended specifications for States to ensure long-term durability and performance in highway applications. This report summarizes the key findings of the project and provides guidance on producing durable SRW
blocks for highway applications.

The document is available online at www.tfhrc.gov/structur/pubs/07021/index.htm. Limited copies are available from FHWA’s R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-111513.

Current Provisions and Needed Research for Lightweight Concrete in Highway Bridges (TechBrief)
Publication No. FHWA-HRT-07-051

This document is a technical summary of an unpublished FHWA report, Synthesis of Research and Provisions Regarding the Use of Lightweight Concrete in Highway Bridges (FHWA Contract No. DTFH61-04-C-00029).

The TechBrief summarizes a synthesis report on completed research and current American Association  of State Highway and Transportation Officials (AASHTO) provisions related to lightweight concrete used in highway bridges. The report provides a reference point for an FHWA research program aimed at addressing perceived shortcomings in the AASHTO specifications for lightweight concrete. The report also makes recommendations for future research efforts, focusing on the use of lightweight concrete in bridge structures.

The TechBrief is available online at www.fhwa.dot.gov/bridge/pubs/07051/07051.pdf.

Hydraulics Laboratory Fact Sheet
Publication No. FHWA-HRT-07-054

This fact sheet describes the major components, accomplishments, expertise, and partners of the J. Sterling Jones Hydraulics Research Laboratory—a state-of-the-art facility at TFHRC used to conduct a variety of experiments pertaining to water. Among other things, the laboratory provides a means of testing the hydraulic properties of submerged bridges, highway drainage structures, and stream crossings. For example, the laboratory gives operational engineers the design tools needed to solve problems with stream stability, develop design standards for bridges in areas with a high risk for floods, and contribute to design standards to address scouring around bridge piers and submerged bridge decks.

TFHRC has more than 24 laboratories for research in the areas of safety; operations, including intelligent transportation systems; materials technology; pavements; structures; and human- centered systems. The expertise of TFHRC scientists and engineers covers more than 20 transportation-related disciplines, and these laboratories are a vital resource for advancing FHWA’s body of knowledge. FHWA’s Office of Research, Development, and Technology operates and manages TFHRC to conduct innovative research to provide solutions to transportation problems both nationwide and internationally. TFHRC is located in McLean, VA. For more information, visit www.tfhrc.gov.

The fact sheet is available online at www.tfhrc.gov/structur/pubs/07054/07054.pdf.

Analysis of an Ultra-High Performance Concrete Two-Way Ribbed Bridge Deck Slab (TechBrief)
Publication No. FHWA-HRT-07-055

This document is a technical summary of an unpublished FHWA report, Analysis of an Ultra-High Performance Concrete Two-Way Ribbed Bridge Deck Slab.

This TechBrief highlights the design process for an ultra-high performance concrete (UHPC), two-way ribbed, prestressed bridge deck element. UHPC is a relatively new material that has demonstrated good durability properties, high compressive strength, and usable tensile resistance. The desirable high compressive and usable tensile resistance can lead to smaller and more efficient precast cross sections. The durability properties of UHPC specifically lend themselves toward use in the most environmentally stressed portions of bridges, namely the decks.

This document is available online at www.fhwa.dot.gov/bridge/pubs/07055/07055.pdf. A printed copy of the report is available only from NTIS under order number PB2007-112112.

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Other Articles in this issue:

PEL: A Path to Streamlining And Stewardship

Scoring Intersection Safety

The Environmental First Lady

PLAN Go Slows

Integrated Corridor Management

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March/April 2008 · Vol. 71 · No. 5