Nemzetközi szemle: Augusztus
Diszaggregált baleseti frekvencia és kockázat modellezés
Disaggregate accident frequency and risk modelling
Lasse Fridstrøm Institute of Transport Economics Norwegian Centre for Transport Research, Norway
Terjedelem: 54 oldal
Accident count data are non-negative integers. A large part of the variation in such data is due to sheer and unexplainable randomness. There are strong reasons to believe that accident data are, at least approximately, Poisson distributed. Acknowledging this fact opens the door to an arsenal of quite efficient inference methods. We explain how these opportunities can be exploited – or missed.
Felületi bevonat teljesítmény mérések – legjobb gyakorlat
Chip Seal Performance Measures – Best Practices
Linda M. Pierce, Nathan Kebede Applied Pavement Technology, Inc.
Washington State Department of Transportation, USA
Terjedelem: 82 oldal
The Washington State Department of Transportation (WSDOT) has a long history of designing, constructing, and maintaining chip seal or bituminous surface treatment pavements. However, to date WSDOT has not developed pavement performance indicators or models to predict chip seal service life, but rather assumes an average life of 6 to 8 years. Due to funding constraints and good pavement management practices, WSDOT has increased the number of pavement segments that are candidates for receiving chip seal applications. In order to improve predictions of chip seal performance and improve their demonstrated cost effectiveness, chip seal performance indicators are needed. The objectives of this research project are to evaluate different performance indicators for chip seal treatments and to develop trigger values for these indicators that will indicate the end of service life and the appropriate index values for resurfacing. Under Phase I of this study, a formal literature review and detailed survey of transportation agency practices were conducted to identify which pavement distress or combination of distresses best characterize the optimal timing for chip seal application. This report summarizes the findings of the literature review, agency survey, WSDOT pavement management and performance modeling practices, and a recommendation of potential performance models for further evaluation as additional data become available.
Termékek, melyek hatással vannak vagy lehetnek a jelenlegi közutas gyakorlatra
Products with an Impact or Potential Impact on Current Highway Practice
NCHRP IDEA Program
Transportation Research Board, USA
Terjedelem: 109 oldal
This report presents a summary of some of the successful projects from the NCHRP IDEA
(Innovations Deserving Exploratory Analysis) program, a special project (SP 20-30) of the National Cooperative Highway Research Program, from its inception in 1993 until present (2015). The two charts at beginning of the report summarize NCHRP IDEA products that have made to the marketplace or show much promise and are followed by some examples in the following categories: Corrosion Protection / Detection, Bridge Construction / Rehabilitation, Bridge Monitoring / Testing, Pavement and Base/Subbase, Materials for Construction / Rehabilitation, Material Testing and Characterization, Highway Safety, Traffic Operations and Safety.
A jelzőlámpa nélküli csomópontok forgalomszabályozási módjának lehetséges megválasztási követelményei a MUTCD (Egységes forgalomszabályozó eszközök kézikönyve) számára
Potential MUTCD Criteria for Selecting the Type of Control for Unsignalized Intersections
Kay Fitzpatrick, Marcus Brewer, Gene Hawkins, Paul Carlson, Vichika Iragavarapu Texas A&M Transportation Institute, USA
Jim Pline, Peter Koonce, Consultants, USA
Terjedelem: 127 oldal
The 2009 Manual on Uniform Traffic Control Devices (MUTCD) includes guidance for the use of various types of traffic control at unsignalized intersections. Despite changes and advances in traffic engineering in recent decades, the MUTCD content related to selection of traffic control in Part 2B has seen only minor changes since 1971. In an effort to update the MUTCD, this research addressed the following types of unsignalized traffic control: no control, yield control, two-way stop control, and all-way stop control. The research team developed recommendations using information available from reviews of existing literature, policies, guidelines, and findings from an economic analysis, along with the engineering judgment of the research team and panel. The language proposed for the next edition of the MUTCD for unsignalized intersections developed at the conclusion of this research is provided in the appendix. It includes consideration of high-speed (rural) and low-speed (urban) conditions along with the number of legs at the intersection. Because the number of expected crashes at an intersection is a function of the number of legs, the decision on appropriate traffic control should also be sensitive to the number of legs present. The proposed language includes introductory general considerations, discusses alternatives to changing right-of-way control, and steps through the various forms of unsignalized control from least restrictive to most restrictive, beginning with no control and concluding with all-way stop control. Supplemental notes are provided to suggested additions to the current text, which show the reader the source(s) of the material and/or the research team’s reasoning for proposing the text.
Alacsony hőmérsékletű aszfaltkeverékekhez alkalmazható habosított aszfalt tulajdonságai
Properties of Foamed Asphalt for Warm Mix Asphalt Applications
David E. Newcomb, Edith Arambula, Fan Yin, Jun Zhang
Amit Bhasin, Wei Li, Zelalem Arega
Texas A&M Transportation Institute, Texas A&M University, USA
Center for Transportation Research, University of Texas, USA
Terjedelem: 133 oldal
This report presents proposed AASHTO standard test methods for measuring performance-related properties of foamed asphalts and designing foamed asphalt mixes with satisfactory aggregate coating and workability. Thus, the report will be of immediate interest to materials engineers in state highway agencies and the construction industry with responsibility for design and production of foamed asphalts and foamed asphalt mixes for warm mix asphalt (WMA) applications.
A megnövelt újrafelhasznált aszfalt arány hatása a nagy sűrűségű súrlódásjavító rétegekre
Perform An Investigation of the Effects of Increased Reclaimed Asphalt Pavement (RAP) Levels in Dense Graded Friction Courses
Reynaldo Roque, Yu Yan, Cristian Cocconcelli, George Lopp
University of Florida, USA
Terjedelem: 133 oldal
In this study, a total of 28 mixture combinations were designed and evaluated to determine the maximum allowable amount of reclaimed asphalt pavement (RAP) material in friction courses without jeopardizing pavement cracking performance. The experimental factors included two RAP sources, four RAP contents, two virgin binders, and two mixture conditioning levels. RAP binder was recovered and blended with virgin binders at various RAP binder replacement ratios. All blended binders not only met the FDOT’s specifications for virgin modified binders, but also had satisfactory binder fracture energy density (FED) values. Increased RAP content resulted in stronger (higher tensile strength) but more brittle (lower failure strain and lower FED) mixtures. However, even after long-term oven aging (LTOA) + cyclic pore pressure conditioning (CPPC), all RAP mixtures exhibited FED values above 0.75 kJ/m3 and ER values well above1.0, indicating adequate cracking performance. Higher RAP content generally resulted in higher ER values. Although the increasing trend was reversed between 30% and 40% RAP content, the ER at 40% RAP was still well above 1.0 and greater than the ER for 20% RAP mixtures. It should be noted that all RAP mixtures evaluated not only met Superpave design criteria, but also dominant aggregate size range and the interstitial component (DASR-IC) requirements. Satisfactory inclusion of up to 40% RAP was for well-designed mixtures with good gradation characteristics and with the use of modified asphalt binders.