January/February 2003
Recent Publications
Compiled by Zac Ellis of FHWA's Office of
Research and Technology Services
Below are brief descriptions of reports recently published by
the Federal Highway Administration's (FHWA) Office of Research, Development,
and
Technology. All of the publications are available from the National
Technical Information Service (NTIS). In some cases, limited copies
are available from the Research and Technology (R&T) Report Center.
When ordering from NTIS, include the NTIS publication 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)
Expanded Sales Desk Hours: 8 a.m. to 8 p.m. EST, Mon.-Fri.
Address requests for items available from the R&T Report Center
to:
R&T Report 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://isweb.tasc.dot.gov/library/library.htm.
Electrochemical Chloride Extraction: Influence of Concrete Surface
on Treatment
Publication No. FHWA-RD-02-107
One bridge restoration technique available for reducing corrosion-induced
concrete deterioration, which removes chloride ions while simultaneously
re-alkalizing the concrete adjacent to the steel, is electrochemical
chloride extraction (ECE). Studies have shown that ECE is capable
of removing, in a single application, a significant portion of the
chloride ions from a reinforced concrete structure. Prior research
also has shown that the quantity of chloride ions removed is dependent
on numerous factors, including quantity and spacing of reinforcing
steel, applied voltage, initial chloride concentration, etc. In addition,
investigations into chloride binding and competition between other
ions as current carriers have helped clarify the probable mechanisms
responsible for decreases in current efficiency with time during chloride
removal.
This portion of the investigation has focused on the influence of
the water-to-cement (w/c) ratio. In addition, an investigation was
conducted to identify the cause of the decrease in efficiency during
chloride removal. A clear relationship between the w/c ratio and the
chloride extraction rate was not evident. However, the investigation
revealed that the resistance of the concrete surface layer increases
considerably during ECE, which effectively restricts the current flow,
while the resistance of the underlying layer of concrete either decreases
or remains constant. It appears that the increased resistance of the
surface layer concrete is accompanied by the formation of a tightly
adhering residue on the concrete surface. Preliminary analysis of
the surface formation indicates it contains carbonate and calcium
chloride.
IHSDM Intersection Diagnostic Review Model Knowledge Base Report
Publication No. FHWA-RD-02-045
This report documents the results of a study on the "Development
of an Expert System for the Interactive Highway Safety Design Model
(IHSDM)." The objective was to develop software to perform a
diagnostic review of intersections on rural two-lane highways, referred
to as the Intersection Diagnostic Review Model (IDRM). The report
focuses on documenting the knowledge base developed for the IDRM software.
It also documents the software in that it identifies the knowledge
structure, problem definitions, models, decision algorithms, formulas,
and parameter values implemented in the software.
Modifications of Highway Air Pollution Models for Complex Site
Geometries, Volume I: Data Analysis And Model Development
Publication No. FHWA-RD-02-036
This is volume I of a two-volume report on a study to improve air
pollution dispersion models for depressed highway sites. The study
assesses limitations of flat terrain and other street-canyon air pollution
models. Experimental results from other documented field and atmospheric
wind tunnel tests, supplemented by those tests conducted during this
study, led to improved concepts and quantification of airflow dynamics
for depressed sites. A comprehensive set of highway cross-sections
and pertinent physical relationships were examined for resultant wind
flows, turbulence, concentration fields, and visual tracer paths.
Modifications of Highway Air Pollution Models for Complex Site
Geometries, Volume II: Wind Tunnel Test Program
Publication No. FHWA-RD-02-037
This is volume II of a two-volume report on a study to increase the
scope and clarity of air pollution models for depressed highway and
street canyon sites. The report presents the atmospheric wind tunnel
program conducted to increase the database and improve physical concepts
of pertinent movements and mixing of air and its contaminants. Wind
tunnel measurements are less costly than field measurements and are
sensitive to controlled input variables.
The first wind tunnel operations assured geometric, vortex structure,
and upstream flow similarity and correct building wake and moving
vehicle effects. Tracer gases from point, line, and moving vehicle
sources were used appropriately. For wind tunnel models of depressed
roads or street canyons, hot-wire anemometer velocity and turbulence,
pressure distribution, and receptor point concentration measurements
were made. Using a selected standard road model which had two dimensions
and a width/height (W/H) ratio of one, effects of wind angle, local
source location, added upwind cuts, vehicle speed, ambient wind speed,
and the presence of upwind wall canopy were observed. Other two-dimensional
tests involved changing the W/H ratios from 0.25 to 6.0, sloping the
walls, slotted walls, walls of unequal heights, and curved roads.
Three-dimensional tests included end effects, intersections, and an
added taller structure along one side of the road. Test results gave
qualitative evaluations, concise tables, graphic illustrations, and
qualitative concepts of wind flows and dispersion.
Other
Articles in this issue:
Saving Lives: A Vital FHWA Goal
Helping Research Pay Off
Safer Roadsides
Making Two-Lane Roads Safer
Driving After Dark
Reducing Points of Conflict
Life in the Crosswalk
Pushing through the Safety Plateau
Data is Key to Understanding and Improving Safety
Managing Speed