March/April 2007 · Vol. 70 · No. 5

March/April 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.

LTPP Product List

Publication No. FHWA-HRT-06-119

FHWA's Long-Term Pavement Performance (LTPP) program is a 20-year study of inservice pavements designed to collect the data required to understand how and why pavements perform the way they do. The U.S. Congress mandated the LTPP program to "prepare products and deliver them to the appropriate customers in a rational, organized manner." To fulfill this mandate, the LTPP program developed the products contained on this list.

This document is available online at www.fhwa.dot.gov/pavement/ltpp/pubs/06119/index.cfm.

FHWA/NHTSA National Crash Analysis Center Fact Sheet
Publication No. FHWA-HRT-06-110

The National Crash Analysis Center (NCAC) is a globally unique storehouse of safety experts and information that focuses on advancing new technologies and tools for analyzing crashes. NCAC primarily supports the U.S. Department of Transportation's strategic goal to reduce fatalities and injuries on the Nation's roadways but also supports efforts to improve safety worldwide.

Shared-Use Path Level of Service Calculator — A User's Guide
Publication No. FHWA-HRT-05-138

Shared-use paths are becoming increasingly busy in many places in the United States. Path designers and operators need guidance on how wide to make new or rebuilt paths and whether to separate the different types of users. The current guidance is not specific, has not been calibrated to conditions in the United States, and does not accommodate the range of modes found on a typical U.S. path. FHWA recently completed a project to develop a method for estimating the level of service (LOS) for shared-use paths that overcomes these limitations. The research included the development of the theory of traffic flow on a path, an extensive effort to collect data on path operations, and a survey during which path users expressed their degree of satisfaction with the paths shown on a series of videos.

Based on the theory developed and the data collected, the researchers developed an LOS estimation method for bicyclists that requires minimal input and produces a simple and useful result. The method requires only four inputs from the user: one-way user volume in the design hour, mode split percentages, trail width, and presence or absence of a centerline. Factors involved in estimating the LOS for a path include the number of times a typical bicyclist meets or passes another path user and the number of those passes that are delayed. The method considers five types of path users when calculating the LOS for an adult bicyclist: other adult bicyclists, child bicyclists, pedestrians, runners, and in-line skaters.

This report provides step-by-step instructions on how to use the LOS procedure and spreadsheet calculation tool, which are available for download from the TFHRC Web site at www.tfhrc.gov. Other products related to this effort include Evaluation of Safety, Design, and Operation of Shared-Use Paths: Final Report (FHWA-HRT-05-137), which documents the research and the spreadsheet calculation tool, and the TechBrief Evaluation of Safety, Design, and Operation of Shared-Use Paths (FHWA-HRT-05-139).

The user's guide document is available online at www.tfhrc.gov/safety/pedbike/pubs/05138/index.htm. The NTIS publication order number is PB2006-114951.

Evaluation of Safety, Design, and Operation of Shared-Use Paths: Final Report
Publication No. FHWA-HRT-05-137

FHWA researchers developed a method for estimating the LOS for bicyclists on shared-use paths that requires minimal input and produces a simple and useful result. Factors involved in the estimation of an LOS for a path include the number of times a typical bicyclist meets or passes another path user, the number of those passes that are delayed, the path width, and whether the path has a centerline. The method considers four other types of path users aside from adult bicyclists, for whom the LOS is calculated — pedestrians, runners, child bicyclists, and in-line skaters.

This report documents the research conducted during the project. Other products related to this effort include Shared-Use Path Level of Service Calculator — A User's Guide (FHWA-HRT-05-138), which documents the LOS procedure and spreadsheet calculation tool, and the TechBrief Evaluation of Safety, Design, and Operation of Shared-Use Paths (FHWA-HRT-05-139).

The NTIS publication order number is PB2006-114284.

A Laboratory and Field Study of Composite Piles For Bridge Substructures
Publication No. FHWA-HRT-04-043

The most commonly used pile materials are steel, concrete, and wood. These materials can degrade, and the degradation rate can be relatively rapid in harsh marine environments. Estimates indicate that the United States spends more than $1 billion annually for repairing and replacing waterfront piling systems. This high cost has spurred interest in alternative composite pile materials such as fiber-reinforced polymers (FRPs), recycled plastics, and hybrid materials. Because only minimal performance data are available for composite piles, FHWA researchers undertook a project to investigate the following by means of field tests and analyses: (1) the behavior of composite piles at the soil-pile interface, (2) the long-term durability of concrete-filled FRP shell composite piles, and (3) the driveability and axial and lateral load response of concrete-filled FRP composite piles and steel-reinforced recycled plastic piles. In addition, FHWA implemented a long-term monitoring program at a bridge over the Hampton River in Virginia.

According to laboratory results, values for the residual interface friction angle between three pile surfaces and a subrounded to rounded sand were 27, 25, and 28 degrees for the FRP composite pile, the recycled plastic pile, and the prestressed concrete pile, respectively. The values of residual interface friction angle between these piles and a subangular to angular sand were 29, 29, and 28 degrees for the FRP composite pile, the recycled plastic pile, and the prestressed concrete pile, respectively. Regarding the durability of FRP composite piles, the researchers found that moisture absorption caused degradation of strength and stiffness in the FRP shells, but freeze-thaw cycles had little effect. Analyses indicated that FRP degradation due to moisture absorption should have minimal impact on axial capacity of the FRP composite piles because most of the axial capacity is provided by the concrete infill. However, FRP degradation has a greater effect on lateral capacity because the FRP shell provides the capacity on the tension side of the pile.

The field tests demonstrated that there were no major differences in driveability among the FRP composite pile, the recycled pile, and the prestressed concrete pile. In static load tests, the FRP composite pile and prestressed concrete pile exhibited similar axial and lateral stiffness, and the plastic pile was significantly less stiff. Conventional static analyses of axial load capacity, axial load versus settlement, and lateral load versus deflection provided reasonable predictions for the composite piles, at least to the levels of accuracy that can be achieved for more common pile materials. FHWA also implemented a long-term monitoring program for an FRP composite pile and a prestressed concrete pile so researchers can compare their load-transfer performance over time. The Virginia Department of Transportation will perform the long-term monitoring.

This document is available online at www.tfhrc.gov/structur/pubs/04043/index.htm. The NTIS publication order number is PB2006-114274.

Geometric Design Laboratory Fact Sheet
Publication No. FHWA-HRT-06-101

The mission of the Geometric Design Laboratory is to provide technical support to the FHWA Office of Safety Research and Development to develop the Interactive Highway Safety Design Model (IHSDM), a suite of software tools for evaluating the safety of highway geometric design alternatives. The current public release of IHSDM is available for download at www.ihsdm.org.

The fact sheet is available online at www.tfhrc.gov/about/gdl.htm.

Optimization of Traffic Data Collection for Specific Pavement Design Applications
Publication No. FHWA-HRT-05-079

The objective of this study is to establish the minimum effort required for collecting traffic data for pavement design applications satisfying a maximum acceptable error under a prescribed confidence level. The approach consists of simulating the traffic data input to the 2002 National Cooperative Highway Research Program (NCHRP) 1-37A design guide for 17 distinct scenarios for collecting traffic data using extended-coverage, weigh-in-motion (WIM) data from the LTPP database. The scenarios include a combination of site-specific, regional, and national WIM data, automated vehicle classification, and automated traffic recorder data of various lengths of coverage. The researchers obtained regional data using clustering techniques and estimated pavement life using mean traffic input and low-percentile input to the NCHRP 1-37A design guide for three levels of confidence: 75 percent, 85 percent, and 95 percent. For each confidence level, the researchers estimated ranges in prediction errors for the pavement life. Then they produced a three-dimensional plot, indicating the maximum error by confidence level for each of the scenarios analyzed. The plot can be used to establish the minimum required effort for collecting traffic data, given the acceptable error and the desirable level of confidence.

This document is available online at www.fhwa.dot.gov/pavement/ltpp/pubs/05079/index.cfm. The NTIS publication order number is PB2006-110476.

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Other Articles in this issue:

Old World Ways

New Lime Test for Hot Mix Asphalt Unveiled

Better Options For Older Adults

Creep and Recovery

Understanding Freight Bottlenecks

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March/April 2007 · Vol. 70 · No.5