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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 - Spring 2020

Spring 2020
Issue No:
Vol. 84 No. 1
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates


Below are brief descriptions of communications products recently developed by the Federal Highway Administration's 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 website 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: 703–605–6050
Toll-free number: 1–888–584–8332

Requests for items available from the R&T Product Distribution Center should be addressed to:

R&T Product Distribution Center
Szanca Solutions/FHWA PDC
700 North 3rd Avenue
Altoona, PA 16601
Telephone: 814–239–1160
Fax: 814–239–2156

For more information on R&T communications products available from FHWA, visit FHWA’s website at, the FHWA Research Library at (or email, or the National Transportation Library at (or email


Safety Evaluation of Continuous Green T Intersections


Publication Number: FHWA-HRT-19-032

Continuous green T (CGT) intersections are an alternative to conventional signalized intersections with three approach legs.

The purpose of the study was to evaluate the safety effectiveness of low-cost safety improvement strategies through scientifically rigorous crash-based studies. One of the strategies evaluated for this study is the use of CGT intersections at three-leg locations. This treatment enables continuous through movement on the major street with a channelized left-turn movement from the minor street onto the major street.

This study examines the safety effectiveness of CGT intersections in terms of crash frequency using the propensity scores–potential outcomes framework. Researchers found that CGT intersections reduced total crashes; fatal and injury crashes; and rear-end, angle, and sideswipe crashes.

Based on the findings of this research and the literature review, CGT intersections are likely to be effective when the following conditions exist: high through-traffic volumes on the major street approach on the far side of the intersection, low bicyclist demand, and no pedestrian demand or another type of pedestrian crossing nearby.

The TechBrief is available at


Traveler Information Requirements During Nonrecurring Events

Publication Number: FHWA-HRT-19-033

This report documents a series of experiments aimed at exploring the specific traveler information messages that are most likely to result in changes in traveler behavior during nonrecurring events. The study highlights the value of information in helping drivers make informed travel decisions.

The report also provides information about how specific components of travel messages are interpreted by drivers and provides recommendations about the type of messaging that can be used to influence travel behavior.

This report is geared to traffic management center operators, agency leadership, transportation engineers and researchers, and others who share an interest in promoting safe and efficient traffic flow.

The report is available at


Safety Evaluation of Pedestrian Countdown Signals

Publication Number: FHWA-HRT-19-045

FHWA established the Development of Crash Modification Factors (DCMF) Program in 2012 to address highway safety research needs for evaluating new and innovative safety strategies by developing reliable quantitative estimates of their effectiveness in reducing crashes. The goal of the DCMF Program is to save lives by identifying new safety strategies that effectively reduce crashes and by promoting those strategies for nationwide implementation. State transportation departments and other transportation agencies need to have objective measures for safety effectiveness and benefit-cost ratios before investing in broad applications of new strategies for safety improvements.

This study investigated the effectiveness of pedestrian countdown signals (PCS). These signals may reduce pedestrian crashes, but also affect other types of crashes. A before/after empirical Bayes analysis was performed using data from 115 treated intersections in Charlotte, NC, and 218 treated intersections in Philadelphia, PA, to evaluate the safety effects of PCSs.

The study results showed that after the implementation of countdown signals, pedestrian crashes decreased by 9 percent, total crashes decreased by 8 percent, and rear-end crashes decreased by 12 percent.

This report will benefit safety and traffic engineers and safety planners by providing greater insight into pedestrian safety.

The full report is available at


Strength and Fatigue Resistance of Clustered Shear Stud Connectors in Composite Steel Girders

Publication Number: FHWA-HRT-20-005

Accelerated bridge construction (ABC) is a technique in which large bridge elements are fabricated offsite or next to the site and are then connected onsite to complete the bridge. One ABC method is the use of full-depth precast concrete deck panels, which are placed on top of steel girders connected via shear studs. The precast concrete deck panels typically have pockets cast into them so that they fit around the shear studs. These pockets are then filled with grout to form the composite connection with the girder. Researchers conducted large- and small-scale fatigue and static tests in this study to evaluate the fatigue, strength, and spacing design provisions from the American Association of State Highway and Transportation Officials (AASHTO) for shear studs. The large-scale tests in this study were constructed with precast concrete deck panels and steel beams.

This report documents the fatigue and static testing of shear stud composite connections between steel girders and precast concrete decks. The static test results suggest that current AASHTO shear stud-strength design provisions are not conservative enough. This is balanced by fatigue test results indicating that current AASHTO shear stud-fatigue provisions are probably too conservative, which explains why there have not been widespread in-service performance problems.

This report will benefit those interested in the design, fabrication, and construction of steel bridges and PC concrete decks, including State transportation departments, bridge design consultants, and PC concrete facilities.

The full report is available at /research/infrastructure/structures/bridge/20005.