Nemzetközi szemle: Április
A laboratóriumi keverék öregítés és az aszfaltkeverék teljesítmény kapcsolata
Szerzők: S. Daniel, F. Yin, A. Epps Martin, E. Arámbula-Mercado, D. Newcomb, J.P. Planche, A. Pauli, M. Farrar, S.C. Huang, G. Reinke, A. Hanz (Transportation Research Board USA)
Terjedelem: 94 oldal
This E-Circular captures the results from TRB Session 462: Relationship of Laboratory Mix. Aging to Asphalt Mixture Performance, which was held during the 95th Annual Meeting of the Transportation Research Board in 2016. Numerous new or improved asphalt mixture testing and procedures are currently being evaluated to try to show relationships to mix field performance. One critical aspect of this work, that needs to be developed, is a lab aging method that will accurately reflect the mix aging in the field. This circular provides four papers on different aspects of addressing this issue. These range from handling the mix at the production facility, to varying the lab mix conditioning, toward capturing real world situations. It also includes the comparison of mix and binder properties from two field projects which shows the relationship to changes with aging of the pavement.
Hogyan javíthatja az elérhetetlenségi index a közlekedéstervezést és a beruházásokat
Szerző: F. Di Ciommo (International Transport Forum OECD)
Terjedelem: 23 oldal
Within the equity in transport framework, this paper will provide an overview on the rationale of using the needs-based approach for transport planning assessment. The paper is structured into three parts. First, the presentation of the needs-based approach using the inaccessibility index. Second, the interpretation of the index through the case of Barcelona. The focus will be on how the inaccessibility index allows us to capture relevant information on the satisfied mobility needs of different population groups (particularly for vulnerable groups of the population) through different transport modes. Finally, the potential incorporation into transport planning/assessment frameworks. This section discusses the ways in which the index could be implemented in two different contexts: ex-ante infrastructure evaluation and assessment of a deprived geographic area for transport strategic planning.
Az elérhetőség tervezésének és kutatásának kihívásai a fenntartható mobilitás mellett
Szerző(k): C. Silva, A. Larsson (International Transport Forum OECD)
Terjedelem: 23 oldal
Accessibility has become a fashionable concept both in the research and policy arena. There has been a growing interest and attention on accessibility measures and on the potential of accessibility based planning as means to invert the growing unsustainability of urban settlement and mobility patterns. Regardless of the potential advantages, current practice has revealed a number of challenges facing accessibility planning and research. This paper presents a reflection on two of these challenges: lack of implementation and conceptual ambiguity of accessibility measures in planning practice. After presenting the main arguments for each challenge, the paper explains how they create risks in the context of sustainable development, namely, by creating biased understandings which prevent authorities and practitioners from shifting away from the traditional “predict and provide” paradigm for transport planning. At the end of each reflection, the paper suggests a research and policy agenda to overcome the challenges supported by the institutionalisation of accessibility planning.
London elérhetőségi mutatói: erősségek, gyengeségek, kihívások
Szerző: A. Inayathusein, S. Cooper (International Transport Forum OECD)
Terjedelem: 39 oldal
The paper provides an introduction to London’s context and the need for accessibility indicators. It overviews existing indicators developed and used by Transport for London, including: PTAL, ATOS (Access to Services) and catchment- based measures, as well as giving an introduction to TfL’s online web portal for connectivity assessment: WebCAT. There is also a review of calculation principles, a summary of user cases and an analysis of the strengths and weaknesses of each method. A second section describes indicators (e.g. PTAL incorporating cycling, and walking catchment analysis) that are currently under development as part of TfL’s commitment towards prioritising healthy streets and sustainable modes of transport. The final section focuses on challenges and opportunities identified during the development of these indicators.
Repülőtér burkolatok meleg aszfalt keverékeinek laboratóriumi teljesítmény vizsgálata
Szerző(k): Mejías-Santiago, J.F. Rushing (U.S. Army Engineer Research and Development Center Geotechnical and Structures Laboratory)
Terjedelem: 51 oldal
In many paving projects, warm-mix asphalt (WMA) has replaced hot-mix asphalt (HMA) as a means of reducing the environmental impacts, which include air pollution, fossil fuel depletion, and smog formation, during production of asphalt mixtures. As state Departments of Transportation (DOT) gain experience with WMA, conventional HMA may become less available for paving. Empirical evidence suggests that WMA performs well under heavy military aircraft loads and can be adopted for use in airfield pavements. However, further research is required to develop guidance for using WMA for commercial airport pavements. Additional laboratory and field performance evaluation of WMA technologies under heavy aircraft loads will provide the information needed to develop such guidance. This report presents a laboratory rutting performance evaluation of WMA compared to HMA. The study includes evaluation of the three main categories of WMA technologies: chemical additive, organic wax, and a foaming process. A laboratory replicated WMA mixtures from two airport paving projects using the same materials and mix design procedures used for construction. The laboratory designed a third mixture using Federal Aviation Administration (FAA) local materials and mix design specifications. The repeated load test, static creep test, indirect tensile strength test, and asphalt pavement analyzer test evaluated all three mixtures for rutting. A mixture for full-scale evaluation of WMA under heavy aircraft loads at the FAA High Temperature Pavement Test Facility (is recommended based on the results.
Alkalmazkodó jelzőlámpás szabályozás megvalósításának teljesítmény alapú működési értékelése Iowa állam Des Moines városában
Szerzők: A. Sharma, N. Hawkins, S. Knickerbocker, S. Poddar, J. Shaw (Iowa State University USA)
Terjedelem: 92 oldal
Maintaining optimal mobility on high-volume arterial traffic corridors is important to transportation agencies and the public. Corridor performance often can be enhanced by updating traffic signal timing, but most agencies find it necessary to prioritize their retiming efforts based on resource constraints. To facilitate prioritization, a set of arterial corridor performance measures was developed using INRIX probe vehicle data. These commercially available data are derived from in-vehicle global positioning system (GPS) observations transmitted wirelessly, eliminating the need for supplemental traffic observation infrastructure to be installed in the field. The main objective of this study was to present a methodology to compare arterial corridors in terms of mobility-based performance measures. This process can help agencies select the corridors that are in need of signal retiming and can help identify corridors suited for adaptive signal control implementation. The two-step methodology began by identifying the number of days in a year with abnormal traffic patterns and comparing the volume-normalized performance of the remaining segments to identify corridors that are problematic on normal days. The proposed methodology was applied to 12 corridors in Des Moines, Iowa, and 1 in Omaha, Nebraska. Three corridors were found to have a high number of anomalous days. Among the remaining corridors, three were identified as under-performing on normal days. In addition, the impact of implementing an adaptive signal control system on one corridor (University Avenue) was evaluated, where small improvements in travel rate and daily variation were observed, but the overall variability increased.
A gyalogos biztonság rendszerszemléletű elemzése
Szerző(k): L. Thomas, L. Sandt, C. Zegeer, W. Kumfer, K. Lang, B. Lan, Z. Horowitz, A. Butsick, J. Toole, R.J. Schneider (University of North Carolina, Kittelson & Associates, Inc. University of Wisconsin, USA)
Terjedelem: 111 oldal
This guidebook was developed to provide a framework for transportation agencies to take the steps needed to advance toward implementing a risk-based, systemic pedestrian safety management process to reduce pedestrian crashes. The guidebook aims to provide a rationale and motivation for taking a systemic approach; clarify key terms and definitions; describe the data needs for a systemic process and offer guidance on how agencies can acquire necessary data; offer guidance for conducting a systemic analysis, as well as provide alternative methods and troubleshooting; and highlight real-world examples that can provide motivation and models for systemic approaches.
Önvezető járművek biztonságának mérése
Szerzők: Fraade-Blanar, M.S. Blumenthal, J.M. Anderson, N. Kalra (RAND Corporation USA)
Terjedelem: 91 oldal
The safety of automated vehicles (AVs) is intrinsic to their success both in the marketplace and as the kind of transformative innovation that their proponents anticipate. In the summer of 2017, the Uber Advanced Technologies Group approached the RAND Corporation to request help in crafting a framework for measuring AV safety that could aid in public discussion of the issues. This project builds on previous RAND research into AV trends and related public policy. Whereas prior work has addressed issues broadly and analytically, this project has looked more closely at what companies that are key to the evolution of AVs have been doing to foster and evaluate the safety of those vehicles. The report is intended for a broad public audience. In this report, we develop a framework for measuring safety in AVs that could be used broadly by companies, policymakers, and the public. We considered how to define safety for AVs, how to measure safety for AVs, and how to communicate what is learned or understood about AVs. Given AVs’ limited total on-road mileage compared with conventional vehicles, we consider options for proxy measurements—i.e., factors that might be correlated with safety. We also explore how safety measurements could be made in simulation and on closed courses. The closely held nature of AV data limits the details of what is made public or shared between companies and with the government. The report focuses on identifying key concepts and illuminating the kinds of measurements that might be made and communicated.
Vékonyréteg beavatkozások javasolt teljesítmény előrebecslő egyenletei és beavatkozási határértékek a hosszú távú burkolatviselkedési adatbázis felhasználásával
Szerzők: M.D. Elwardany, K. Lee, J.H. Lee, C. Brown, C. Castorena, Y.R. Kim (North Carolina State University USA)
Terjedelem: 36 oldal
The purpose of pavement-preservation treatments is to correct surface defects, improve ride quality, improve safety characteristics, and extend pavement life without increasing the structural capacity of the pavement. The application of a thin overlay is expected to extend the life of a pavement by 8–10 year, although this range may vary depending on traffic, environmental conditions, quality of the materials, and workmanship. Thin overlays do not significantly increase the structural capacity of a pavement. Thus, the existing pavement condition should be evaluated carefully prior to the application of a thin overlay to ensure that structural rehabilitation is not necessary. A set of guidelines to determine the best time to apply thin-overlay treatments would help highway agencies optimize their budgets, thereby leading to potentially significant taxpayer savings. The objective of this study was to develop guidelines, parameters, and performance-prediction equations to select the most appropriate time to apply a thin-overlay treatment based on the condition of the existing pavement. To arrive at the proposed guidelines, data from the Long-Term Pavement Performance (LTPP) Program Specific
Pavement Studies 3 and 5 were used to evaluate the effects of climate, traffic, existing asphalt concrete (AC)–layer thickness, and overlay thickness on the life extension that results from the application of thin-overlay treatments. The results demonstrate that threshold triggers based on longitudinal cracking in the wheel path and rutting severity can be used to select the best time to apply a thin overlay in order to achieve a target pavement-life extension. Analysis of the LTPP data shows that both the traffic level and existing AC-layer thickness significantly affect the life extension that results from the application of a thin overlay in terms of retarding rutting and longitudinal cracking, respectively. This paper presents empirical equations to predict the life gain that can be achieved from a thin-overlay treatment based on the existing pavement conditions.
Felkészülés a közlekedés jövőjére – Önvezető járművek 3.0
Szerzők: U.S. Department of Transportation
Terjedelem: 80 oldal
Preparing for the Future of Transportation: Automated Vehicles 3.0 (AV 3.0) advances U.S. DOT’s commitment to supporting the safe, reliable, efficient, and cost-effective integration of automation into the broader multimodal surface transportation system. AV 3.0 builds upon—but does not replace—voluntary guidance provided in Automated Driving Systems 2.0: A Vision for Safety. Automation technologies are new and rapidly evolving. The right approach to achieving safety improvements begins with a focus on removing unnecessary barriers and issuing voluntary guidance, rather than regulations that could stifle innovation. In AV 3.0, U.S. DOT’s surface transportation operating administrations come together for the first time to publish a Departmental policy statement on automation. This document incorporates feedback from manufacturers and technology developers, infrastructure owners and operators, commercial motor carriers, the bus transit industry, and State and local governments.2 This document considers automation broadly, addressing all levels of automation (SAE automation Levels 1 to 5), and recognizes multimodal interests in the full range of capabilities this technology can offer.