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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 - July/August 2014

July/August 2014
Issue No:
Vol. 78 No. 1
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

Where Pedestrians Cross the Roadway (TechBrief)

Publication Number: FHWA-HRT-13-099

dep10In 2010, 13 percent of all crash fatalities were pedestrians. Of these, 68.1 percent occurred outside of intersections. Despite the large proportion of crashes, there has been little research investigating why pedestrians cross roadways at unmarked locations.

This TechBrief describes research on the environmental influences of where and when pedestrians cross roadways, using observations at 20 sites in the Washington, DC, metropolitan area. The study team coded and analyzed the circumstances surrounding when and where pedestrian crossings took place for more than 70,000 crossings, then created a model to predict crossing behaviors. These data have the potential to guide roadway design and aid in the selection and location of pedestrian crossing interventions, such as crossing beacons, ultimately increasing pedestrian safety in shared-use environments.

Researchers coded pedestrian roadway crossings at 20 locations, each one block in length and flanked by two marked crosswalks at intersections. The research team then recorded crossings within one marked, signal-controlled crosswalk and the roadway between it and the next marked crossing (but not within the far crossing). Daytime pedestrian crossings were coded for several different factors, including location (within the marked crosswalk or not), traffic status (a WALK or DON’T WALK signal illuminated), yielding (pedestrians yielding to vehicles or vehicles yielding to pedestrians in the roadway), and evasive actions (any evasive movement made by a vehicle or pedestrian to avoid collision, such as running or abrupt braking).

The team also recorded environmental features of each location, including the distance between the marked crosswalks, the average annual daily traffic volume, street directionality (one- or two-way), and physical barriers in or along the roadway that might prevent pedestrians from crossing easily.

The end result is a model created from the collected data that predicts where pedestrians are likely to cross the road (marked intersection crosswalk or nonintersection). The accuracy of the model ranged from 80.55 percent to 95.22 percent based on location. The model correctly predicted a mean of 90 percent of crossings, and overall it was successful in predicting whether participants would cross at marked crosswalks at intersections or outside of a marked crossing.

The researchers recommend that when designing in areas where pedestrian traffic exists, planners should evaluate the environmental features to determine where pedestrian crossings are most likely. Areas that have a high predicted likelihood of unmarked, nonintersection crossings could be targeted to modify the crossing affordances of the environment, increasing safety and meeting the needs of all road users.

This technical brief is available to download at Printed copies are available from the PDC.

Corrosion Monitoring Research of New York City Bridges (TechBrief)

Publication Number: FHWA-HRT-14-024

dep11Currently, all State and local agencies responsible for maintaining suspension bridge cables base their maintenance plans primarily on previous experiences and on information from limited inspections. Usually, inspectors evaluate the exterior covering of the cables biannually.

If agencies suspect deterioration problems, and if their maintenance budgets permit, they conduct indepth inspections. Inspectors unwrap the cable at a few locations along its length and perform a visual inspection of the condition of the wires and, in some cases, cut and remove a few wires for laboratory testing.

Unfortunately, current visual inspections do not provide sufficiently reliable data, indicating the need for innovative nondestructive testing and sensing technologies. Such technologies could provide comprehensive and reliable assessment of cable conditions over time either directly or through measurable variables, such as temperature and humidity.

This technical brief discusses a project for which researchers installed a network of sensors to monitor the internal environment of the main cables of suspension bridges and to record the cables’ condition and deterioration over time. The project also evaluated the most promising nondestructive testing technologies for direct detection of corrosion damage inside the main cables.

Researchers conducted a literature review and a series of validation tests of the available techniques and sensors for corrosion monitoring. The goals were to determine the state of the art of the currently available sensor technologies, especially corrosion monitoring techniques, and to see whether these sensors and technologies could be applied to the monitoring of main cables in suspension bridges.

The study demonstrated that direct monitoring is possible. The information provided by such a system can be used to make more reliable estimations of the safety factor and remaining service life.

This technical brief is available to download at Printed copies are available from the PDC.

Methodology for Analysis of Soluble Salts From Steel Substrates (Summary Report)

Publication Number: FHWA-HRT-14-026

dep12There are many sources of soluble salts on steel bridges, including atmospheric contaminants and deicing chemicals. Even abrasives for cleaning steel surfaces sometimes contain a detrimental amount of soluble salts, which can deposit additional salts during blast cleaning instead of fully removing existing salt residue. This summary report discusses a study designed to evaluate extraction and analysis methods for determining the amount of soluble salts on steel substrates.

There is no method that can extract all salt contaminants from steel surfaces, especially for rusted steel substrates with pits. The effectiveness of each extraction method varies. For this study, researchers tested three extraction methods. The first was a paint test cell, in which a glass tube is clamped onto a steel plate with an O-ring to keep the point of contact watertight. The second was the latex sleeve method, which is part of a field test kit. The third extraction method involved boiling a steel plate in deionized water. Each method produced a solution that could be tested for soluble salt levels to compare the effectiveness of the extraction.

Researchers analyzed the extraction solutions through ion chromatography, using anion concentration to represent the amount of salts in a sample. The three anions that commonly exist on steel bridge surfaces are chloride, sulfate, and nitrate. Ion chromatography can determine the concentrations of all three anions simultaneously with accuracy below 1 part per million.

Researchers found that the boiling method has better efficiency than the paint test cell method. Both methods used deionized water as extracting media. The proprietary chloride extraction solution used in the latex sleeve method extracted more soluble salts from steel surfaces than deionized water.

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

Performance-Based Contractor Prequalification as An Alternative to Performance Bonds (TechBrief)

Publication Number: FHWA-HRT-14-035

dep13In the highway industry, one of the primary considerations in prequalifying a contractor is determining whether a performance bond can be secured. Performance bonds are not insurance and do not guarantee the quality of the work. They come into play only when the contractor has defaulted on completion of the contract and is in financial default. When two bidding companies have the same level of financial assets, the current performance bonding system does not differentiate between high-performing and marginally performing contractors. Generally, the system does not evaluate contractors in terms of the completion of timely, high-quality work that satisfies the expectations of State department of transportation (DOT) decisionmakers.

This technical brief discusses the results of a study that consisted of a detailed literature review; surveys of contractors, State DOTs, and sureties; and State DOT case studies. Researchers examined the benefits and costs of performance bonds and performance-based contractor prequalification and created a three-tier, performance-based model for prequalifying contractors.

The study results suggest that the minimum contract value that requires a performance bond should be raised to between $1 million and $10 million and that the cost of performance-based prequalification is low compared to the cost of the premiums for performance bonds.

Researchers developed a model for contractor prequalification based on performance and financials that rewards good performance and encourages improvement of marginal performance. The model is general enough that individual transportation departments will be able to adapt it to their own specific conditions. It is intended to guide State DOTs in making their existing systems more robust and to take into account the performance of the contractor when awarding projects.

A brief description of the model and its three tiers is included in this technical brief, as well as some guidance on implementation through the identification of the business decisions for each tier.

This document is available to download at Printed copies are available from the PDC.