Nemzetközi szemle: Február
A mérsékelten meleg aszfalt technológia értékelése hajlékony burkolatokon
Evaluation of Warm Mix Asphalt Technology in Flexible Pavements
Szerzők: Mohammad, A. Raghavendra, M. Medeiros, M. Hassan, W. King (Louisiana State University USA)
Terjedelem: 200 oldal
Kivonat:
Warm mix asphalt (WMA) describes various technologies that allow asphalt mixtures to be produced at lower temperatures as compared to hot mix asphalt (HMA). WMA technologies also offer improvements in workability, cost, and environmental sustainability such as reduced fuel usage, greenhouse gas emissions, and wear and tear at plants, while enhancing worker health and safety conditions. The primary objective of this study was to evaluate the laboratory performance of plant-produced lab-compacted mixtures utilizing various WMA technologies, including some mixtures with higher percentages of RAP. The secondary objective of this study was to compare WMA energy consumption cost and emission data to conventional HMA mixtures in terms of fuel/energy savings at the plant and in terms of CO and CO2 emissions. Six projects in Louisiana utilizing four different WMA technologies were considered in this study, yielding 20 mixtures total. Each project included a companion HMA mixture section to allow for direct comparison. Loose mixtures were obtained from trucks at the plant and compacted on-site in a mobile asphalt laboratory. Laboratory tests included dynamic modulus (|E*|), flow number (FN), loaded wheel tracking (LWT) test, indirect tensile (IDT) test, semi-circular bend (SCB) test, thermal stress restrained specimen test (TSRST), and the Lottman moisture susceptibility test. Results indicated that WMA mixtures exhibit similar high and intermediate temperature performances in the laboratory as compared to HMA. On average, $1.61 of energy savings per ton of produced asphalt mixture was observed, along with a considerable reduction in air pollutants at the plant. However, the cost of additives and royalty fees would reduce the total cost savings from using WMA. These benefits were observed without reduction in the mechanistic performance of the mix.
Többcélú optimálás a mechanikai-tapasztalati pályaszerkezet tervezési útmutató teljesítmény modelljeinek jobb kalibrálásához
Szerzők: N. Kargah-Ostadi, J.R. Menendez, M. Zhou (Fugro Consultants, Inc. USA)
Terjedelem: 156 oldal
Kivonat:
This research study devised two scenarios for application of multi-objective optimization to enhance calibration of performance models in the American Association of State Highway and Transportation Officials (AASHTO) AASHTOWare® Pavement ME Design software. In the primary scenario, mean and standard deviation of prediction error are simultaneously minimized to increase accuracy and precision at the same time. In the second scenario, model prediction error on data from Federal Highway Administration’s Long-Term Pavement Performance test sections and error on available accelerated pavement testing data are treated as independent objective functions to be minimized simultaneously. The multi-objective optimization results in a final pool of tradeoff solutions, where none of the viable sets of calibration factors are eliminated prematurely. Exploring the final front results in more reasonable calibration coefficients that could not be identified using single-objective approaches. This report demonstrates the application of engineering judgment and qualitative criteria to select reasonable calibration coefficients from the final pool of solutions that result from the multi-objective optimization. More reasonable calibration factors result in a more justifiable pavement design considering multiple aspects of pavement performance. This investigation revealed that simply evaluating the bias and standard error is not adequate for a comprehensive evaluation of performance prediction models.
Magánberuházás a közlekedési infrastruktúrába. A bizonytalanság kezelése a szerződésekben
Private Investment in Transport Infrastructure. Dealing with Uncertainty in Contracts
Szerző: The International Transport Forum (OECD)
Terjedelem: 125 oldal
Kivonat:
This report presents the synthesis of the results of a Working Group convened by the International Transport Forum (ITF) to review current thinking on private investment in transport infrastructure. In particular it examines the ways in which uncertainty affects contracts – in the procurement and management of large infrastructure projects.
Alkalmazkodó jelzőlámpás szabályozás
Szerzők: S. Radin, L. Chajka-Cadin, E. Futcher, J. Badgley, J. Mittleman, John A. Volpe (National Transportation Systems Center USA)
Terjedelem: 122 oldal
Kivonat:
As part of the Federal Highway Administration’s (FHWA) Research and Technology Program evaluation, this report documents the findings of a summative evaluation of various adaptive signal control technology (ASCT) research and outreach activities conducted by FHWA over the course of more than 20 yr. The evaluation considers the ways in which FHWA’s investment in ASCT research and related outreach activities have influenced the development and deployment of these technologies. The evaluation also addresses the short-term impacts of ASCT deployments, including reduced traffic congestion and delays. Due to the extended timeline of the program, the research and outreach activities were chronologically categorized into three distinct phases, and each was evaluated on its influence on ASCT development and deployment. This report also identifies challenges and lessons learned that may be applied to further intelligent transportation systems research.
Burkolati adalékanyag minőségi követelményei
Aggregate Quality Requirements for Pavements
Szerzők: E. Tutumluer, M. Moaveni, I.I.A. Qamhia (Advanced Transportation Geotechnics Solutions, LLC USA)
Terjedelem: 103 oldal
Kivonat:
Constructing and maintaining pavements requires an abundant and dependable supply of quality aggregates. Aggregate comes from a wide range of materials, including quarried rock, sand, and gravel, and materials such as slag, reclaimed asphalt pavement, and recycled concrete aggregate. While all transportation agencies have specifications for aggregate quality, there is wide variation in what different agencies consider suitable aggregates for specific applications. This synthesis documents transportation agency requirements for the quality of aggregates for various pavement types. Information used in this study was gathered through a literature review and a survey of state departments of transportation and Canadian provincial transportation agencies.
A közösségi közlekedés, a megosztott mobilitás és a személygépkocsi használat kölcsönhatásainak jobb megértése
Szerzők: S. Feigon, C. Murphy (Shared-Use Mobility Center USA)
Terjedelem: 92 oldal
Kivonat:
TCRP Research Report 195: Broadening Understanding of the Interplay Among Public Transit, Shared Mobility, and Personal Automobiles extends the research presented in TCRP Research Report 188: Shared Mobility and the Transformation of Public Transit. It broadens understanding of the interplay between emerging and established modes of transportation by further exploring how shared modes, particularly transportation network companies, are being incorporated into the mix of transportation options. This report will help transit agencies and other public entities to better understand the opportunities and challenges as they relate to technology-enabled mobility services.
Mobiltelefon adatok értékelése az átlagos napi forgalom becsléséhez
Evaluating Cell Phone Data for AADT Estimation
Szerzők: J. Codjoe, G. Ashley, W. Saunders (Louisiana Transportation Research Center USA)
Terjedelem: 95 oldal
Kivonat:
AADT estimation facilitates the process of determining and prioritizing funds for both road safety and improvement projects. Traffic counts over non-state roadways are normally the responsibility of local governments and the Metropolitan Planning Organizations of Louisiana’s major cities. Other non-state roadways in rural and small urban areas do not have such systemic traffic counts or estimation programs so these areas tend to lack timely traffic volumes across non-state and local roads. Streetlytics is being considered as a potential supplement for systemically providing AADTs on all state and non-state roadways within Louisiana. In this study, a bivariate correlation analysis and quantitative analysis (percentage difference) were used to evaluate the comparability of Streetlytics’ volume counts with traditional DOTD counts. Simple linear regression was then used to develop predictive models that accounted for the differences between the two datasets. The data was analyzed on three levels to compare Traditional count data to Streetlytics counts. Level 1 comprised all data, level 2 comprised Routine count data versus Permanent count data, and level 3 comprised Observed locations versus Unobserved locations. Overall, the results confirmed strong positive correlation between Streetlytics data and Traditional count data. The study recommends adoption of the On-Premises dataset of Streetlytics to supplement the efforts of DOTD’s Traffic Monitoring Unit.
Összefüggés a közösségi közlekedési vagyon állapota és a szolgáltatás minősége között
The Relationship Between Transit Asset Condition and Service Quality
Szerzők: Transportation Research Board USA
Terjedelem: 122 oldal
Kivonat:
Maintaining transit assets, such as vehicles, guideway and facilities in good repair enables transit agencies to maximize the quality of the service they provide and minimize transit agency and passenger costs over time. As assets deteriorate in condition they tend to become more unreliable, requiring more maintenance and becoming more likely to fail in service. Likewise, improving asset conditions typically results in reduced maintenance costs and increased asset reliability. Passengers’ perceptions of the conditions of transit vehicles and facilities can impact the overall quality of their journey, and regardless of those perceptions passengers may experience increased delay as a result of asset failures. Previously the link between transit service quality and asset condition, while understood at an intuitive level, was not well quantified. The research described in this report explores the different dimensions of transit service quantity, describing how these may relate to physical asset conditions. Also, it proposes an overall measure of service quality termed Effective Journey Time (EJT). This measure captures the total time a passenger spends for a transit trip, with adjustments for the quality of the time from the passenger’s perspective. Asset conditions impact EJT in two basic ways: through asset failures that may generate delay; and through adjustments for customer perceptions that vary as a function of condition. Four case studies have been performed illustrating use of EJT for illustrating impacts of changes in asset conditions for vehicles and facilities for bus and rail systems.
Kerékpáros kapuk. Kerékpáros mozgások vizsgálata jelzőlámpás kerékpáros kapukban
Cycle gates. Understanding bicycle movements at traffic light controlled cycle gates
Szerzők: S. Greenshields, M. Gupta, A. Wells (Transport Research Laboratory UK)
Terjedelem: 31 oldal
Kivonat:
Cycle gates have recently been introduced in London, as a method of separating cycle traffic and general traffic at signal-controlled junctions where a significant proportion of motor vehicles turn left. This report presents the findings of research into road user behaviour and attitudes at two cycle gates on Cycle Superhighways. Video recordings were made at the two sites and analysed to identify cyclists’ choice of route through the junction and motorists’ and cyclists’ compliance with signals while passing through.
Habosított bitumennel stabilizált burkolatok tervezése és teljesítménye
Design and Performance of Foamed Bitumen Stabilised Pavements
(letölthető ingyenes regisztrációval)
Szerzők: R. Yeo (Austroads Australia)
Terjedelem: 310 oldal
Kivonat:
There is a need to improve the Austroads procedures for mix design and structural design of foamed bitumen stabilised (FBS) materials. This final report summarises the mix design test methods developed within the context of an Austroads mix design process. The report details the construction and performance monitoring of six trial sections. It was observed that cracking was the predominant distress type and that pavement thickness design needs to consider FBS fatigue. The observed fatigue lives were reasonably consistent with the predictions of the Austroads interim method. Generally, rutting and shape loss are not dominating performance, even when the host material stabilised includes 20% recycled asphalt.