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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 - November/December 2016

November/December 2016
Issue No:
Vol. 80 No. 3
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates

by Lisa A. Shuler 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
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 Web site at, the FHWA Research Library at (or email, or the National Transportation Library at (or email

Dimensional Stability of Grout-Type Materials Used as Connections for Prefabricated Bridge Elements (Report)

Publication Number: FHWA-HRT-16-008

dep8_4This report discusses research focused on addressing performance concerns related to the dimensional stability (primarily early-age shrinkage) of 11 commercially available grouts and grout-like materials. Bridge engineers and material specifiers have observed that some materials in these classes, especially those classified as nonshrink grouts, may display significant dimensional instability when used in connection details during bridge construction projects. This shrinkage results in cracking and leakage through the grout or at interfaces with prefabricated components.

This report summarizes research demonstrating the types of shrinkage expected from these grouts, the shortcomings of commonly used test methods, alternative test methods that may better demonstrate real-world performance, and an innovative way of minimizing the shrinkage observed in some of the grouts.

The most common test methods used to evaluate dimensional stability are described in the ASTM (formerly the American Society for Testing and Materials) C1107 test method. After an initial evaluation, researchers found that the methods in this specification consider several parameters simultaneously, providing a qualitative approach that is only useful for comparative purposes. To evaluate the variety of parameters more completely, researchers assessed volume changes from a fundamental standpoint, measuring pure expansion and shrinkage deformations via test methods such as ASTM C157 and ASTM C1698. Results showed that most of the grouts evaluated in this research performed well in terms of dimensional stability when tested in accordance with ASTM C1107.

However, separate testing to assess autogenous and drying deformations (shrinkage and expansion) demonstrated that ASTM C1107 is not necessarily an appropriate means to capture the full range of critical dimensional stability behaviors. Given the fact that most of the cement-based grouts commonly exhibit shrinkage, this research also included additional tests focused on mitigating partial shrinkage by including internal curing through the use of prewetted lightweight aggregates.

This report is available to download at

Safety Evaluation of Continuous Green T Intersections (Report)

Publication Number: FHWA-HRT-16-036

dep9_4The continuous green T intersection is characterized by a channelized left-turn movement from the minor street approach onto the major street, along with a continuous through movement on the major street. The continuous through movement typically has a green through arrow indicator to inform drivers that they do not have to stop.

This report documents research conducted as part of FHWA’s Evaluation of Low-Cost Safety Improvements Pooled Fund Study to provide crash modification factors and benefit-cost economic analyses for targeted safety strategies.

Past research has consistently demonstrated operational and environmental benefits from implementing the continuous green T intersection at three-leg locations when compared with a conventional signalized T intersection. These benefits include reduced delays, fuel consumption, and emissions. The safety effects of the conventional signalized T intersection are less clear. Past research has been limited to a small sample of intersections in a single State and used only simple statistical comparisons from reported crash data.

To overcome the statistical challenges associated with prior safety studies and improve product reliability, researchers used a propensity scores-potential outcomes framework--which can be used to mimic a randomized experiment--to compare the safety performance of the continuous green T intersection with the conventional signalized T intersection. The study examined 30 treatment sites and 38 comparison sites from Florida, and 16treatment sites and 21 comparison sites from South Carolina. Results showed that the expected total, fatal and injury, and target crash (rear-end, angle, and sideswipe) frequencies were lower at the continuous green T intersections relative to the conventional signalized T intersections.

The benefit-cost analysis indicated that the continuous green T intersection is a cost-effective alternative to the traditional, signalized T intersection. The report also provides additional details and results of the safety evaluation.

The document is available to download at

User-Friendly Traffic Incident Management (TIM) Program Benefit-Cost Estimation Tool, Version 1.2 (Report)

Publication Number: FHWA-HRT-16-055

dep10_4Traffic incidents contribute significantly to the deterioration of the level of service of both freeways and arterials. Traffic incident management (TIM) programs have been introduced worldwide with the aim of mitigating the impact of traffic incidents on safety and roadway performance. These programs support quick incident response, thereby shortening incident duration, and control traffic demand around the incident scene.

Some TIM programs can be costly to taxpayers. Therefore, it is important for transportation agencies to evaluate the benefits of TIM programs and determine the associated return on investment. Benefit-cost estimation studies for TIM programs have employed a range of estimation methodologies and monetary equivalent conversion factors. Consequently, resulting benefit-cost ratio estimates vary widely.

This report includes an overview of TIM (various strategies and their benefits, costs, and stakeholders) and methodology information (selected strategies, duration and proportion-based estimation, data collection based on microscopic simulation, benefit estimation modeling, cost calculation, the benefit-cost ratio, and additional benefits).

The report also discusses a benefit-cost tool with standardized methodology that can be employed universally and equitably in estimating benefit-cost ratios for different TIM programs. This is essential for establishing consistency and greater confidence in the validity of results. With access to the methodology in the form of a simple-to-use, less data-intensive tool, TIM programs and taxpayers alike can benefit from cost-effective evaluations.

The report also includes a case study of the I–95 Corridor Coalition in New York. The case study features a comparison of the effectiveness of implementing three selected TIM strategies--safety service patrol, driver removal laws, and dispatch colocation. It also advances an understanding of the need for a standardized tool to estimate benefit-cost ratios and the effectiveness of the developed TIM benefit-cost tool.

The report is available to download at The tool is available at