U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Public Roads This magazine is an archived publication and may contain dated technical, contact, and link information. |
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| Publication Number: FHWA-HRT-16-006 Date: September/October 2016 |
Publication Number:
FHWA-HRT-16-006
Issue No: Vol. 80 No. 2 Date: September/October 2016 |
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 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
5301 Shawnee Road
Alexandria, VA 22312
Telephone: 703–605–6000
Toll-free number: 1–888–584–8332
Web site: www.ntis.gov
Email: customerservice@ntis.gov
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
Email: report.center@dot.gov
For more information on R&T communications products available from FHWA, visit FHWA’s Web site at www.fhwa.dot.gov, the FHWA Research Library at www.fhwa.dot.gov/research/library (or email fhwalibrary@dot.gov), or the National Transportation Library at ntl.bts.gov (or email library@dot.gov).
This technical brief discusses an evaluation of intersection conflict warning systems conducted under the Evaluation of Low Cost Safety Improvements Pooled Fund Study, which currently has 40 State members. These systems intend to reduce the frequency of crashes by alerting drivers to conflicting vehicles on adjacent approaches at unsignalized intersections.
Researchers obtained geometric, traffic, and crash data for four-legged, rural, two-way, STOP-controlled intersections with conflict warning system installations in Minnesota, Missouri, and North Carolina. To account for potential selection bias, researchers conducted an empirical Bayes before-after analysis using reference groups of similar four-legged, rural, two-way STOP-controlled intersections without the warning systems installed.
The analysis also controlled for changes in traffic volumes over time and time trends in crash counts unrelated to the strategy. The combined results for all States indicated statistically significant crash reductions for most crash types for intersections of two two-lane roads and for intersections of a four-lane road with a two-lane road.
The results suggest that the implementation of intersection conflict warning systems--even with conservative assumptions on cost, service life, and the value of a statistical life--can be cost effective. Because this is an evolving strategy, the results of this study reflect installation practices to date.
This document is available to download at www.fhwa.dot.gov/publications/research/safety/15076/index.cfm.
The use of engineered fills with and without layered reinforced soil systems is an economical solution to reduce deformations and improve bearing resistance of shallow foundations for bridge supports. Engineered fills, including compacted granular fill and reinforced soil, are a cost-effective alternative to conventional bridge foundation systems. But limited guidance exists for estimating the settlement and lateral deformation of these features under service conditions. In addition, transportation engineers do not fully understand the stress distribution within these features, leading to uncertainty about their performance.
To address these gaps, FHWA initiated a study to evaluate the design and analysis of the service limit state--the condition beyond which a structure or component no longer fulfills the intended performance--of engineered fills for bridge support. This synthesis report is the product of an extensive literature search on current practices, available load tests, and numerical modeling results. It presents factors impacting the service limit of engineered fills, such as reinforcement conditions and backfill types, and also provides a preliminary analysis of the reliability of existing prediction methods.
Engineered fills can support bridge abutments and piers with various configurations. Bridge supports using reinforced engineered fills contribute to better compatibility of deformation between the components of bridge systems, minimizing the effects of differential settlements and the occurrence of undesirable “bumps” between the bridge deck and approach embankment transitions.
Despite the benefits, many transportation agencies do not consider shallow foundation alternatives for a variety of reasons, including concerns related to meeting serviceability requirements. The service limit state for shallow foundations often controls the design of bridge foundations; however, little guidance is available for engineered fills. This report will assist in the continued development of research efforts to establish design guidance on the service limit state for the use of engineered fills.
The document is available to download at www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/15080/index.cfm.
One strategy of cooperative vehicle-highway systems is speed harmonization, which dynamically adjusts vehicle speed recommendations to reduce speed differentials. Highway agencies can use speed harmonization near areas of congestion, crashes, or special events to optimize mobility and safety. This report describes a preliminary experiment on vehicle-to-infrastructure (V2I)-based speed harmonization in which speed guidance is communicated directly to vehicles. The document covers a set of microsimulation experiments and a limited number of prototype field runs, including site selection, setup, and analysis.
A few locations in the United States have implemented speed harmonization with some success, using variable speed limit signs or dynamic message signs. However, this method is susceptible to unpredictable and uncoordinated driver responses. Moreover, the signs are costly for State and local agencies to deploy, operate, and maintain.
Researchers explored an alternative in a project that involved implementing speed harmonization algorithms on an active freeway with recurring spatially structured congestion. The project involved simulation and field testing using a fleet of connected and automated vehicles. The field experiment demonstrated that these vehicles, with automation in the form of modifications to the original equipment manufacturer-supplied adaptive cruise control, can be used to implement V2I-based speed harmonization. Researchers measured the impacts on the traffic stream using probe vehicles leading and following the connected and automated vehicles.
This report is available to download at www.fhwa.dot.gov/publications/research/operations/16023/index.cfm.
Wearable sensors are small and robust enough to be carried directly on a person’s body, such as in a wristband or jewelry, or built into a smartphone. Researchers frequently use them to collect data on environmental, physiological, activity, and location variables. This report summarizes an initial stage investigation into wearable sensors for transportation research applications.
Transportation researchers are interested in the application of wearable sensors to improve existing research and to open up avenues for new research. As recent advances in hardware, connectivity, and data analysis have converged, wearable sensors are now inexpensive, reliable, and widely available. These advances may enable researchers to address a wide variety of transportation research questions. For example, wearable sensors could provide a way to use GPS technology to track subjects’ movements in a way that is less intrusive and more accurate than traditional travel diaries, and potentially less intrusive than using a subject’s smartphone. Wearable sensors also enable travel-behavior studies in areas and among populations where smartphone use might not be high (such as among the elderly or low-income populations).
This report discusses research focused on air quality, physiological, and activity sensors. Researchers found that wearable sensor technology is generally ready for a range of transportation applications. The devices are small, efficient, and accurate. Research-grade devices are fairly expensive, but commercial-grade sensors that take advantage of the power of smartphones can create a wealth of usable data that are becoming easier to obtain and analyze. Techniques and tools to analyze large volumes of data collected from wearable sensors are becoming more widespread, but data management is still an area that needs improvement.
This document is available to download at www.fhwa.dot.gov/advancedresearch/pubs/16034/index.cfm.
