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United States Department of Transportation United States Department of Transportation

Public Roads - January/February 2011

January/February 2011
Issue No:
Vol. 74 No. 4
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates

by Zachary Ellis 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
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-605-6000
Toll-free number: 800-553-NTIS (6847)
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 Turner-Fairbank Highway Research Center's Web site at, the National Transportation Library's Web site at, or the OneDOT information network at

Evaluation of Lane Reduction "Road Diet" Measures on Crashes (Summary Report)

Publication No. FHWA-HRT-10-053

Front page of Evaluation of Lane Reduction "Road Diet" Measures on Crashes (Summary Report). A road diet involves narrowing or eliminating travel lanes on a roadway to make more room for pedestrians and bicyclists. Although there can be more than four travel lanes before treatment, road diets often are conversions of four-lane, undivided roads into three lanes -- two through-lanes plus a center turn lane. The fourth lane might be converted to a bicycle lane, sidewalk, or onstreet parking. This summary replaces Evaluation of Lane Reduction "Road Diet" Measures and Their Effects on Crashes and Injuries (FHWA-HRT-04-082), which described an evaluation of road diet treatments in cities in California and Washington. For this summary, researchers reexamined those data using more advanced study techniques and added an analysis of road diet sites in smaller urban communities in Iowa.

The basic objective of this reanalysis was to estimate the change in total crashes in each of the two databases resulting from the conversions and to combine those estimates into a crash modification factor. To do this, researchers used the empirical Bayes method, which calculates the expected crash frequency of a particular site. The evaluation indicated a statistically significant effect of the road diet treatment in each of the two datasets and when the results are combined. The Iowa data indicate a 47 percent reduction in total crashes while the California and Washington data indicate a 19 percent decrease -- a difference probably due to the differences in traffic volumes and types of urban environments where the treatments were implemented. The reanalysis results also differ from the original Iowa study results (25 percent reduction) and from the original California and Washington results (6 percent reduction). Combining both datasets results in a 29 percent reduction in total crashes.

The document is available at Printed copies also are available from the PDC.

Benefits of High Volume Fly Ash: New Concrete Mixtures Provide Financial, Environmental, and Performance Gains (Fact Sheet)

Publication No. FHWA-HRT-10-051

High volume fly ash (HVFA) concrete mixtures offer many benefits, including decreased cost, reduced energy content, enhanced environmental sustainability, and improved long-term performance. To identify innovative methods to overcome barriers to HVFA use in pavements and transportation structures, the FHWA Exploratory Advanced Research (EAR) Program is sponsoring a study called Greatly Increased Use of Fly Ash in Hydraulic Cement Concrete for Pavement Layers and Transportation Structures. This fact sheet from the study discusses obstacles to HVFA use, how the project is moving forward, areas examined, and how the project might affect the future of concrete.

Many producers and transportation agencies aim to increase the use of fly ash in transportation infrastructure; however, several barriers exist to implementing new mixtures. A particular concern of many practitioners is the difficulty of predicting strength gain in full-scale structures. This ongoing EAR project addresses the problem using temperature management software and the development of a database with analytical prediction tools.

In addition, agencies and contractors are concerned about potential incompatibilities between fly ash, admixtures, and cement. Therefore, the project team is developing screening procedures to identify the influence and properties of residual carbon on the rate of admixture absorption. The goal is to implement innovative strategies such as fly ash treatment, timing and rate of admixture addition, and prescreening of components to improve overall performance. The project is scheduled to be completed in fall 2011.

The document is available at Printed copies are available from the PDC.

An Evaluation of Signing for Three-Lane Roundabouts (Summary Report)

Publication No. FHWA-HRT-10-030

Front page of An Evaluation of Signing for Three-Lane Roundabouts (Summary Report).Although multilane roundabouts have been found to be safer than conventional alternatives, they are not without safety challenges. FHWA studied driver reaction through driving simulations using three selected signing conditions on the approaches to three-lane roundabouts. In addition, FHWA sent questionnaires to participants to identify signing and marking strategies that result in higher levels of comprehension and compliance in lane selection on the approach to roundabouts. This summary report discusses the objectives, approach, method, driving simulation study, results, and recommendations.

One of the challenges of using multilane roundabouts is getting motorists to select and stay in their proper lanes as they navigate the roundabout. Another challenge is that motorists sometimes have difficulty interpreting lane control arrows in the roundabout context. Even with these unresolved issues, the safety and operational advantages of one- and two-lane roundabouts are so substantial that engineers have begun to introduce three-lane roundabouts where traffic cannot be accommodated in one or two lanes.

For roundabouts with three entering lanes, the study found that overhead advance navigation signage is more effective than other types of signage. In addition, it appears that additional treatments beyond the overhead signs tested in this study are needed to keep drivers from changing lanes within roundabouts.

The document is available at Printed copies are available from the PDC.

Crash Impact of Smooth Lane Narrowing with Rumble Strips at Two-Lane Rural Stop-Controlled Intersections (TechBrief)

Publication No. FHWA-HRT-10-047

According to the National Highway Traffic Safety Administration, fatal crashes at unsignalized rural intersections constitute approximately 37 percent of all fatal crashes at intersections nationwide. About 90 percent of the crashes at unsignalized rural intersections occur on two-lane roads. As a low-cost remedy to address this type of crash, FHWA developed and evaluated a treatment to reduce approach speeds by narrowing lanes using rumble strips in the median and on the right-lane edge. This summary report provides information on typical field design features, analytical methods and findings, conclusions, and recommendations for future deployments.

For this study, the lane narrowing was applied to approximately 150 feet (45.7 meters) on the major road approach to two-way stop-controlled intersections on high-speed rural roads. Researchers applied the treatment to eight intersections in five States and collected crash data for the pre- and post-treatment periods. They then used the empirical Bayes method to estimate the effectiveness of the treatment in enhancing safety. The method showed that, on average, the lane narrowing reduced the total number of crashes by 32 percent, while it reduced fatal/injury crashes by 34 percent.

The document is available at Printed copies are available from the PDC.