Communication product updates: compiled by Michael thorn of FHWA's office of corporate research, technology, and innovation management.
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for more information on R&T communications products available from FHWA visit FHWA's Web site at www.fbwa.dot.gov/research/library (or email email@example.com), or the National Transportation library at ntl.bts.gov (or email firstname.lastname@example.org).
Field Evaluation of a Restricted Crossing U-Turn Intersection (Report) Publication Number: FHWA-HRT-11-067
In rural areas, left turns and through movements onto or across four-lane divided access highways too often result in serious crashes. The restricted crossing U-turn intersection design is intended to address this safety issue. This report highlights the results of a study involving observations of driver performance at such an intersection in Maryland. The report also summarizes the results of an empirical Bayes crash analysis performed for intersections along two Maryland corridors before and after conversion to a restricted crossing U-turn.
The observation portion of the study was intended to support design guidance for future designs of restricted crossing U-turns. The researchers focused on the differences between conventional and restricted crossing U-turn intersections in the following areas: conflicts between vehicles, merging behaviors, lag acceptance, weaving, and travel times. They performed crash analyses to examine the effects of converting intersections from conventional to restricted crossing 11-turns along two rural high-speed divided highway corridors. These analyses focused on nine restricted crossing U-turn intersections built between 1998 and 2003.
Researchers used three methods of analysis and ultimately determined that the restricted crossing U-turn design reduced crashes between 28 and 44 percent. The crash data suggest that the overall severity of crashes is lower with the restricted crossing U-turn design than at conventional stop-controlled intersections. Researchers observed a 70 percent reduction in fatal crashes and a 42 percent reduction in crashes that resulted in injuries.
Further, the researchers concluded that the restricted crossing U-turn design should be considered for minor road intersections with four-lane divided highways where there is a sufficient volume of traffic on the minor road. The design greatly reduces the probability of angle crashes at the cost of a minimal increase in travel time. As volume on the divided highway increases, the travel time penalty is likely to decline, and the safety benefit is likely to increase.
This report should be useful to traffic engineers, planners, and officials who are considering safety improvements at unsignalized intersections on four-lane divided highways. It is available to download at www.fhwa.dot.gov/publications/research/safety/hsis/11067/index.cfm. Printed copies are available from the PDC.
Long-Term Plan for Concrete Pavement Research and Technology--The Concrete Pavement Road Map (Second Generation) Volume II, Tracks (Report) Publication Number: FHWA-HRT-11-070
To realize its potential in the 21st century, the concrete paving industry has identified trends that call for dramatic improvements. FHWA and its industry partners are looking to implement these improvements through a holistic approach and using a carefully developed and aggressively implemented strategic plan for research and technology transfer. The Long-Term Plan for Concrete Pavement Research and Technology, also known as the Concrete Pavement (CP) Road Map, tracks and facilitates technologies that will help the concrete pavement community meet current and future needs.
This report is the second of two volumes. The first addresses the need for the CP Road Map and describes its background and development, critical issues and objectives, and a research management plan. The second details the 12 tracks of planned and ongoing research, with more than 270 research problem statements grouped into the tracks. Each track begins with introductory material that summarizes the objectives for the track and the gaps and challenges for its research program. A table of estimated costs provides the projected cost range for each problem statement, which depends on research priorities and the scope determined in implementation.
The 12 tracks are expected to lead to specific products that will change the way concrete pavements are designed and constructed. Ultimately, FHWA and its partners intend the CP Road Map to help move new and useful products and systems quickly and efficiently into practice.
This report is available to download at www.fhwa.dot.gm/publications/research/infrastructure/pavements/pccp/11070/index.cfm. Printed copies are available from the PDC.
Relating Ride Quality and Structural Adequacy for Pavement Rehabilitation And Management Decisions (TechBrief) Publication Number: FHWA-HRT-12-046
Ride quality and structural adequacy are key indicators of pavement performance, hut how do they relate to each other? This TechBrief presents major findings and conclusions from a study sponsored by FHWA to determine the relationship between these indicators using data from the Long-Term Pavement Performance program.
Researchers generated continuous plots for International Roughness Index, effective pavement structural number for flexible pavements, and effective concrete slab thickness for rigid pavements. They did not observe a viable relationship between the two parameters in the sections and data investigated.
The researchers discovery of a lack of correlation could be of value to pavement management system practitioners, as it indicates that good ride quality does not mean good structural adequacy or vice versa. This is an important consideration for those who want to base performance measures on ride quality indicators. Although pavement functional and structural performances are not independent of each other, they are not related in a one-to-one manner that can easily be implemented within a pavement management system. A strong relationship between these two performance indicators would likely require the inclusion of many other variables, limiting its usefulness.
The TechBrief is available to download at www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/12046/index.cfm. Printed copies are available from the PDC.
Safety Evaluation of Transverse Rumble Strips On Approaches to Stop-Controlled Intersections In Rural Areas (Summary Report) Publication Number: FHWA-HRT-12-047
Transverse rumble strips are designed to provide drivers with a tactile and audible warning signal to slow down. Although some crash-based studies have shown that rumble strips are effective in reducing intersection approach speeds, the results from these studies are not reliable when examining crash data. This summary report highlights a study of rumble strips on approaches to stop-controlled intersections in rural areas. It details the impact of transverse rumble strips on total crashes, injury crashes, and specific crash types, such as right-angle and run-STOP-sign crashes.
The study investigated the safety effect of transverse rumble strips on approaches to stop-controlled intersections using an empirical Bayes methodology. Results indicate that rumble strips may be effective in reducing severe injury crashes at stop-controlled intersections on minor roads. However, the researchers noted an increase in crashes involving property damage only. Although they could not definitively state the reasons for this tradeoff, a limited economic analysis indicated a reduction in crash harm of about $6,600 per intersection per year due to the installation of transverse rumble strips.
Since most rumble strips are installed at rural intersections with relatively low volumes and few crashes, statistically significant results require a large sample of intersections with long before-and-after periods, especially since the reduction appears to be in severe injury crashes only. The researchers note that further study on this topic should collect data from other states that have implemented transverse rumble strips and examine the effect on other crash types, such as run-off-road and sideswipe crashes at or near intersections. Additional research should also investigate the effectiveness of this treatment under a variety of conditions, including the number of driveways, nature of the surrounding development and roadside hazards, and sight distance.
This summary report is available to download at www.fhwa.dot.gov/publications/research/safety/hsis/12047/index.cfm. Printed copies are available from the PDC.