November/December 2007 · Vol. 71 · No. 3

November/December 2007

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 research and technology publications from FHWA, visit the Turner-Fairbank Highway Research Center's (TFHRC) Web site at www.tfhrc.gov, FHWA's Web site at www.fhwa.dot.gov, the National Transportation Library's Web site at http://ntl.bts.gov, or the OneDOT information network at http://dotlibrary.dot.gov.

Optimized Sections for High-Strength Concrete Bridge Girders — Effect of Deck Concrete Strength
Publication No. FHWA-HRT-05-058

For more than 25 years, concretes with compressive strengths in excess of 41 megapascals, MPa (6,000 pounds per square inch, psi), have been used in the construction of highrise building columns. Although the availability of high-strength concretes initially was limited to a few geographic locations, now there are more opportunities to use these concretes across the Nation. The technology to produce higher strength concretes has developed primarily within the ready-mix concrete industry for use in buildings, but researchers are now applying the same technology for use in concretes for bridge girders and decks.

Engineers have been concerned about the durability of concrete bridge decks for many years, resulting in the development of numerous strategies to improve performance. Many factors that enable production of a durable concrete also result in a high-strength product. Consequently, a durable concrete bridge deck is likely to have a high compressive strength. This report evaluates the effect of high performance concrete (HPC) on the cost and structural performance of bridge decks and high-strength girder construction. The report investigates several areas with the potential for improved structural performance through the use of HPCs.

This document is available online at www.tfhrc.gov/structur/pubs/05058/index.htm. Limited copies are available from FHWA's R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-106399.

Long-Term Pavement Performance Program
Falling Weight Deflectometer Maintenance Manual
Publication No. FHWA-HRT-05-153

FHWA's Long-Term Pavement Performance (LTPP) program operates eight Dynatest^® Model 8000 Falling Weight Deflectometers (FWDs) to collect deflection data on test sections of inservice pavements across the Nation. The LTPP program collected deflection data during daily operations for 15 years, giving the FWDs very little downtime. To keep the complex hydraulic, electrical, and mechanical FWDs operating effectively under demanding conditions, engineers continuously focused on preventive maintenance. A dedicated maintenance regime also was important to collecting high-quality data and ensuring that the equipment would pass rigorous annual reference calibrations. The owner's manual produced by the manufacturer provides guidance on most repairs and troubleshooting; however, eventually FWDs require service beyond routine maintenance — in other words, the time comes for a complete overhaul.

In spring 2003, one of the contractors overhauled an FWD it operated on behalf of the LTPP program. During the overhaul, the contractor documented the process with photos and described the process for disassembling and reassembling the FWD components and subcomponents. This document provides FWD owners, operators, and technicians with continuous operation maintenance guidelines to complement the owner's manual for the Dynatest^® Model 8000.

This document is available online at www.fhwa.dot.gov/pavement/ltpp/pubs/05153. Copies are available from FHWA's R&T Product Distribution Center.

Long-Term Pavement Performance Program
Manual for Falling Weight Deflectometer Measurements, Version 4.1
Publication No. FHWA-HRT-06-132

This document provides background information and field operations guidelines for collecting FWD data on LTPP test sections. It includes equipment setup and calibration, test locations, and test procedures.

This is the fourth major version of the LTPP Manual for Falling Weight Deflectometer Measurements.
The first two were developed under the auspices of the Strategic Highway Research Program, while the latter two were completed under contract to FHWA. The latest revisions in this manual reflect changes in the data needs of the LTPP program and updates to the FWD equipment.

Current information and access to other technical references are available at http://www.fhwa.dot.gov/pavement/ltpp/. Copies are available from FHWA's R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-101960. To submit requests for LTPP data, technical questions, or user feedback, contact LTPP customer service by e-mail at ltppinfo@fhwa.dot.gov.

Advanced Quality Systems: Guidelines for Establishing and Maintaining Construction
Quality Databases
Publication No. FHWA-HRT-07-019

The main objective of this study was to develop and present guidelines for establishing and maintaining database systems for construction quality issues in asphalt and concrete paving projects for State highway agencies. The study included a literature search and review, followed by a survey of construction quality practices at nine States and a more detailed review of practices at four of those States.

The information collected from survey responses and indepth interviews provided insights about the agencies' databases, data categories, analyses performed, links to other State databases, and reports generated. Results indicated that the nature of the collected information, level of detail, and duration of time over which this information is retained differ significantly from agency to agency. In addition, the current systems differ considerably in their architecture, purpose, data collection, and access procedures.

On a broad scale, the study revealed that agencies are somewhat "data rich and information poor" and are "mostly focused on entering, not retrieving data." Also, because of poor linkages between construction quality and pavement performance and cost data, there is a very limited ability to "close the loop" by showing how improvements in specifications and construction affect performance and life-cycle costs.

In addition to documenting these and other observations and findings, the report presents a detailed description of the features and capabilities of an ideal database on construction quality. It provides illustrative examples of how to improve the overall quality of highway pavement projects. The recommended database is a Web-based system with client server architecture. The system should contain modules (described in detail in the report) for the database server, quality assurance (QA) of input data, QA management, and data translation (referencing).

This document is available online at www.fhwa.dot.gov/pavement/concrete/pubs/07019/index.cfm. Copies are available from FHWA's R&T Product Distribution Center. The document also is available from NTIS under order number PB2007-103341.

Safety Assessment of Interchange Spacing on Urban Freeways (TechBrief)
Publication No. FHWA-HRT-07-031

The decision to build a new interchange between an existing pair of interchanges involves evaluating whether there is sufficient need for traffic to enter and/or exit the freeway at that location. The obvious intent is to reduce the systemwide travel times and delays for motorists by providing convenient freeway access and egress.

Although there are ways to evaluate these operational benefits quantitatively, researchers have been unable to measure the impact of a proposed interchange in terms of safety or the number of crashes per mile of freeway. This knowledge is essential for conducting a comprehensive cost-benefit analysis of new interchange projects. To fill this void, FHWA developed this TechBrief, which covers interchange spacing from a safety perspective by estimating regression models to express crash frequencies as a function of highway characteristics, including interchange spacing. The TechBrief also explores use of regression models to quantify the relationship between interchange spacing and fatal and injury crashes. The data used to build the regression models pertained to freeway sections from 7 urban freeways in California and 10 urban areas in Washington State.

This document is available online at www.tfhrc.gov/safety/pubs/07031/index.htm. Limited copies are available from FHWA's R&T Product Distribution Center.

Traffic Performance of Three Typical Designs of New Jersey Jughandle Intersections (TechBrief)
Publication No. FHWA-HRT-07-032

Although New Jersey jughandle intersections (NJJIs) have been around for more than five decades, researchers had not yet developed a simplified procedure to evaluate their performance in handling traffic compared to conventional at-grade intersections. A limited number of studies reported qualitative and quantitative comparisons of NJJIs, but traffic engineers and planners lacked readily available tools to estimate average delays, numbers of stops, and maximum queues.

For this study, researchers used the traffic simulation tool VISSIM to model typical geometries over a wide distribution of traffic flow conditions for three NJJI designs. Comparisons of NJJIs with conventional intersections for similar volume conditions revealed that NJJIs produced lower average intersection delays and higher intersection capacities for near-saturated traffic conditions and similar traffic performance for undersaturated conditions. Practitioners can use statistical models documented in this study to assess average intersection delays, average numbers of stops per vehicle, and maximum queue lengths for three types of NJJIs — forward ramps, U-turn ramps, and reverse ramps.

This document is available online at www.tfhrc.gov/safety/pubs/07032/index.htm. Limited copies are available from FHWA's R&T Product Distribution Center.

Synthesis of the Median U-Turn Intersection Treatment, Safety, and Operational Benefits (TechBrief)
Publication No. FHWA-HRT-07-033

In the United States, congestion at intersections throughout urban and suburban areas continues to worsen and the number of crashes reported at intersections continues to increase. One potential treatment to combat congestion and safety problems at intersections is the Median U-Turn Intersection Treatment (MUTIT). Used extensively in Michigan for many years, the MUTIT was successfully implemented in Florida, Louisiana, Maryland, and New Jersey in recent years. The treatment eliminates direct left turns at signal-controlled intersections from major and/or minor approaches. Agencies can implement the MUTIT with or without signal control at median openings on a major road.

This synthesis summarizes the advantages and disadvantages of the MUTIT compared to conventional, at-grade, signal-controlled intersections with left turns permitted from all approaches. This TechBrief includes guidelines for the location and design of median crossovers on major roads. Many of the guidelines are borrowed from the Michigan Department of Transportation and address directional and bidirectional crossovers and widened areas called "loons" that facilitate the U-turn maneuver at roads with narrow medians and make it easier for larger vehicles to execute the turn. The TechBrief also presents information on the capacity and crash experience at MUTIT intersections relative to traditional intersections.

This document is available online at www.tfhrc.gov/safety/pubs/07033/index.htm. Limited copies are available from FHWA's R&T Product Distribution Center.

---

Other Articles in this issue:

The Greening of Public Roadsides

Senior Mobility Series: Article 8 New Vehicle Technologies May Help Older Drivers

Spotlight on Transportation Planning

A New Look at Sensors

---

November/December 2007 · Vol. 71 · No.3