The hypothesis that exposure to traffic-related air pollution increases the risk of developing different illnesses (e.g., cancer during childhood) has been demonstrated by various investigators (Crouse et al., 2010; Hamra et al., 2015). Therefore, the need for urban air quality prediction associated with transportation policies is important for health impact assessment (Bhalla et al., 2014; De Nazelle et al., 2011). However, only a few modeling tools are able to include projection in associated traffic related parameters (e.g., traffic allocation) in the prediction of future air quality concentrations and the impact of population mobility on urban air pollution is often ignored. Estimating the various states of air quality associated with transport policies, infrastructure investments and individuals’ mobility are keys to more meaningful urban design and development.
This study presents an innovative design for an air pollution data collection campaign on two sides of the road during the winter months, using a portable weather station in order to assess the effects of meteorology at street level. Despite the low predictive power of the statistical models (which are only meant to be used to understand the strengths of certain predictors), our results themselves provide insight into the complex nature of near-road air pollution.
We highlight the important role of meteorological factors such as temperature, humidity, wind speed, and wind direction. It is also worth noting that although land use variables were not included in the final model explaining mean UFP concentrations, their indirect impacts could be interpreted by the presence of wind direction as a random effect. In addition, traffic was also shown to be a notable contributor in explaining variations in UFP concentrations.
With regards to the absolute UFP difference on two sides of the road, the primary finding was that wind orthogonality and speed act as important predictors. Winds orthogonal to the road have a tendency to increase differences on two sides of the road. However, the most substantial impact on air pollution was the presence of buildings on both sides of the road, which is evidently common in major cities.
The purpose of this analysis is to derive an improved understanding of how Canadian households view electric vehicles of varying types and whether they are seen, or could be seen, as viable household vehicles. The data for this analysis were derived from a sample of approximately 20,000 Canadian households accessed via an online survey panel. The survey was offered in both official languages. Participants were screened against three criteria: age (older than 18), whether respondent is one of the decision-makers in most or all important financial decisions made by the household, and whether the household is at least somewhat likely to purchase or lease a new or used vehicle sometime within the next several years.
The focus of this paper was to evaluate the potential transportation and environmental impacts from different electric vehicle (EV) adoption and urban forms scenarios in the Windsor Census Metropolitan Area (CMA) in 2031. The results reinforce some of the previous findings in the literature. It is found that a compact urban development coupled with significant EV adoption can lead to significant reduction in energy and emissions. This in turn will promote sustainable transportation outcomes in the region. While the conducted analysis mainly relied on conventional techniques (linear regression and 4-stage modeling), the results are sensible and shed light on the role that EVs can play to reduce emissions and energy consumption in the future.
Canada’s engagement in COP 21 and the statements made by the Prime Minister reaffirm the country’s commitment to combating climate change, and the federal government’s intentions to play a more instrumental role in driving down emissions in Canada and abroad. Canada plans to reduce its greenhouse gas (GHG) emissions by 30 per cent below 2005 levels by 2030.
While nearly 30 per cent of Canada's GHG can be attributed to the transportation sector, the policy approach to addressing emissions within the sector has been fragmented and developed in a bit-part way. Only four of ten provinces have a policy regime in place to address emissions, of which three apply (or intend to apply) cap and trade mechanisms and one relies on taxation. In Ontario and Quebec, certain segments of the aviation and shipping industries are excluded entirely.
For railway carriers with operations spanning multiple political boundaries, the resulting effect is a requirement to participate in a series of regional initiatives that lack cohesion and have been brought forward in uncoordinated way.
Canada’s railway industry has a long history of working with the federal government to reduce emissions produced by locomotives. Since 1995, the industry has held a series of Memorandum of Understanding (MOU) with the Federal Minister of Transport that have provided the platform for identifying pragmatic solutions for reducing emissions. The sector is currently working through its third MOU which establishes voluntary GHG emission reduction targets from 2011 to 2016 for Class I freight, shortline, and intercity passenger railways
Conventional asphalt mixture design methodologies such as Superpave, Marshall, and Hveem are used to determine the optimum asphalt binder content by means of physical and volumetric laboratory measurements. All three procedures ensure the materials proportion and quantity of the asphalt cement binder are adequate to meet stability and durability concerns. However, with the increased use of recycled materials, there is a need to develop laboratory mechanical tests in order to evaluate the quality of the asphalt cement binder to complement the Superpave volumetric mixture design procedure. An important component to successful mixture design is the balance between volumetric composition and material compatibility. Balanced asphalt mixture design offers innovation in designing mixtures for performance and evaluation of the quality of a mix design relative to the anticipated performance using a rational approach. This research documents the selection of laboratory mechanical tests, in addition to volumetric requirements, that can ascertain a mixture’s resistance to common asphalt pavement distresses. Factors in the selection of laboratory mechanical tests such as availability of standard test procedures, advantages and limitations, laboratory-to-field correlations, and sensitivity to mixture composition are reviewed. Further, an implementation framework and case histories is also discussed.
This paper briefly presents the development, implementation, and challenges of balanced mix design method in Texas.
Mix durability related performance issues have been observed in recent years with a commonly reported contributing factor being a deficiency in mix asphalt binder content. In many instances, these performance issues are occurring with mixes that have met all governing mix specifications. As a result, asphalt mix specifications are changing rapidly as agencies search for solutions to improve durability. Lower design gyrations (Ndesign), lower target air voids, and increased voids in the mineral aggregate (VMA) are among the implemented specification modifications. Often, individual specification changes are implemented without evaluating their potential conflict with other specification items or at a rate that makes establishing true “cause and effect” on mix performance difficult or impossible to determine.
Oldcastle Materials recognizes the need for improved mix performance and has developed a framework for an Optimized Mix Design Approach (OMEGA) in which innovation and mix engineering efforts are emphasized. The ultimate design approach objective is determining the optimum mix binder content for the specific mix design application (e.g., design traffic, pavement layer location, climate, etc.). This is accomplished through an enhanced materials evaluation and selection process, along with appropriate performance testing (stability and durability/cracking) to help ensure the desired end result performance is provided by the designed mix.
Presentations and Discussion: Bitumen's World Market (Read,J); Input from Europe (Airey,G); Input from India and the Far East (Krishnan,JM); Current Situation and Challenges of Asphalt in the Middle East (Tabatabaee,N), and; Use of Rubber in Bitumen Modification and Interaction between Rubber and Bitumen (Sousa,J). Presentation slides on the CDROM, discussion in print and on CDROM.
Mix testing that can properly characterize cracking of asphalt pavements is one of the most relevant present day issues for the industry. The 91st Annual Meeting (AM) of the Association of Asphalt Paving Technologists (AAPT) provides evidence to this effect as, in the assessment of the authors, cracking was far and away the meeting’s prevailing theme. The 91st AAPT AM began with a Leading Edge Workshop (LEW) that focused exclusively on cracking and associated test methods, and a key factor in most of the remaining content presented at the meeting was cracking. This paper stemmed from the 91st AM LEW in response to cracking’s perceived prevalence in the minds of so many AAPT members.
The primary objective of this paper is to provide the state of the art in asphalt mix cracking from the perspective of the authors and to use this perspective to explain what has been accomplished in the cracking arena and what needs to be accomplished. First, a historical perspective beginning in the mid-1950s and ending in present day is presented that is generally divided into pre and post Superpave mix design. With this historical perspective as a reference, emphasis is shifted to the AM and LEW as they pertained to cracking. A set of prevailing themes was established and used as a segue into discussion of cracking test methods (first what has been accomplished and then what needs to be accomplished). Six areas were identified by the authors where advancement needs to be made with regard to mitigation of cracking: 1) closing the gap between the state of the art and the state of practice; 2) evaluating rapid mix test methods usable during production; 3) emphasizing education; 4) improving reliance on accelerated pavement testing; 5) improving cracking models; and 6) performing large test programs where parallel testing occurs on comparable mixes by way of several test methods.
Oxidative aging can lead to the susceptibility of asphalt pavement to cracking. Most studies on oxidative aging of asphalt binders are related to the prediction of the aging properties of asphalt binders based on oxidation kinetics. Development of kinetics models often involves short-term and long-term aging in the laboratory of original binder at different temperatures and for different times, and experiments of original and aged binder. However, for many rehabilitation projects or forensic studies, the original materials of pavements that were constructed years ago are not readily available to develop kinetic models. The development of a kinetic model based on asphalt binder in an in-service pavement is greatly needed to predict the properties of asphalt binder subjected to further aging for the purpose of overlay design, or to backcalculate the original properties of binder before aging for the purpose of forensic studies.
This study develops a methodology to develop Arrhenius kinetics aging models using asphalt binders that already have been aged, instead of using original binders. Five asphalt binders (one neat and four modified) were included in this study and were subjected to three stage aging. The carbonyl areas of the aged binders were determined using Fourier transform infrared spectroscopy, and the rheological properties and damage properties were determined using a dynamic shear rheometer (DSR). First, the relationships among the model parameters of the oxidation kinetics models for the crossover modulus, DSR function, shear strength, and critical strain energy density of the asphalt binders were developed based on aging of original materials. Based on the relationships between model parameters and experiment results of asphalt binders that have been aged separately, Arrhenius kinetics aging models were developed. The effectiveness of these models which are developed based on aged binder were verified. The developed kinetic models for crossover modulus, DSR function, shear strength, and critical strain energy density of the asphalt binders can be used to predict the properties of asphalt binders subjected to further aging in the field for the design of overlays in the Mechanistic-Empirical Pavement Design Guide or Pavement ME, or to determine the properties of original asphalt binders before aging for the purposes of forensic studies, based on the cumulative aging effects of in-service pavement temperatures.
Application of geogrids for asphalt layers in road and airport pavements has been studied since early 1980’s. This type of geosynthetics is feasible to mitigate reflective cracking and to prolong fatigue life, i.e. to reinforce asphalt layers within a pavement structure. Up to now, many laboratory and field studies have demonstrated significant benefits of using geogrids but still several aspects of their working mechanism within adjacent asphalt layers remain not fully understood and need to be further explored. This paper presents an initial part of a long-term study initiated in Poland in order to fully assess the benefits of using geogrids within asphalt layers. The first part of this paper presents a state-of-the-art review on geogrid applications in asphalt layers. The next part demonstrates and discusses the results obtained on geogrid reinforced beams under monotonic and cyclic loading conditions. Three types of large beams were prepared under laboratory conditions. One group comprises reference beams without any reinforcement and the other two were reinforced, respectively, with glass and carbon geogrids. Specimens were evaluated in a custom-made 3PB/4PB fixture at 13ºC in order to observe their behavior under force-controlled fatigue test and displacement-controlled fracture test. Results demonstrated a beneficial impact of fiber reinforcement on the development of beam deflections in the fatigue tests and significantly higher fracture energy in the post-peak softening region. These results will be used to prepare a new experimental campaign to closely investigate the reinforcement mechanism of geogrids within asphalt layers. The paper concludes with short- and long-term plans necessary to develop an official design procedure for the pavements with geogrid reinforced asphalt layers in Poland.
Warm-mix asphalt (WMA) technologies have been used extensively in the last decade. The benefits of WMA have motivated contractors and agencies to expedite the implementation of this technology. However, some research studies have raised concerns regarding WMA laboratory performance in terms of resistance to moisture damage, while WMA has demonstrated good performance in the field. These experiences motivated further research to understand the fundamental characteristics of WMA. This study comprised a comprehensive evaluation of WMA prepared using different aggregate sources, asphalt binders, and WMA additives. A dynamic mechanical analyzer was used to test the mastic phase of conventional hot-mix asphalt and WMA. The test specimens were evaluated at different conditions—dry and wet—and at different aging stages—unaged and 3-month aged—in a controlled environmental room (i.e. 60°C). A fracture mechanics approach was used to analyze the test results. This approach incorporated fundamental material properties including adhesive bond energy between aggregates and asphalt binder. The results show that WMA performance improved with aging and the overall performance of the WMA can be improved if the selection of materials (i.e., aggregate source, asphalt binder, WMA technology) is optimized based on the compatibility of their surface energy. In addition, surface energy results were able to explain some findings from the mechanical testing related to moisture susceptibility of WMA.
Low temperature cracking is a serious distress for asphalt pavement built in cold regions, such as the northern U.S. and northern Europe. Therefore, accurate assessment of the strength and fracture properties of asphalt mixtures is fundamental for ensuring the long term integrity of the entire pavement structure. It has been shown that asphalt mixtures behave in a quasibrittle manner at low temperatures and, consequently, their nominal strength strongly depends on the structure size. Most of the research performed in the past has experimentally addressed this phenomenon either on unnotched or deep-notched specimens corresponding to Type I and Type II size effects, respectively. However, the evolution of the pavement conditions during the service life can lead to the formation and propagation of cracks which strongly affect the response of the material and, eventually, determine a complex size effect. In this paper a comprehensive experimental study is performed to evaluate the effect of different notch depths on the scaling law for quasibrittle fracture. Three-point bending tests are performed on plain and notched asphalt mixture beams of different sizes at low temperature. The results on unnotched specimens are analyzed through the Type I energetic-statistical size effect law (SEL) in combination with the weakest link model, while, in the case of deep notched specimens, the Type II SEL is used. A significant variation in the evolution of the SEL is observed with a dramatic decrease in strength over size and notch length. In addition, an empirical relation between the initial fracture energy, Gf, and the total fracture energy, GF, is found, and the characteristic length, cf, associated to the length of fracture process zone, is determined.
The use of recycled asphalt shingles (RAS) as a partial replacement for petroleum-based virgin asphalt binder has received considerable attention in recent years. The objective of this study is to correlate the molecular structure and corresponding compositional analysis of asphalt binders of conventional asphalt mixtures as well as of mixtures containing recycled asphalt shingles (RAS) and/or reclaimed asphalt pavement (RAP) with their cracking potential at intermediate temperature. Laboratory testing evaluated the molecular composition of asphalt binders obtained from asphalt mixtures evaluated in this study using thin layer chromatograph/FID (Iatroscan) and gel permeation chromatography (GPC). Fracture resistance of laboratory-produced mixtures was assessed using the semicircular bend (SCB) test at intermediate temperature. Molecular fractionation through GPC of RAS samples confirmed the presence of associated asphaltenes in greater concentrations than recycled asphalt pavement (RAP) samples. High concentrations of high molecular weight asphaltenes decrease the fracture resistance of the asphalt mixtures. The use of rejuvenating agents, Cyclogen-L, Hydrogreen, asphalt flux and re-refined engine oil bottoms (REOB), did not reduce the concentration of the highly associated asphaltenes; further they failed to improve the cracking resistance of the asphalt mixtures evaluated in this study.
As more reclaimed asphalt pavement (RAP) is utilized in asphalt mixtures, there are increasing concerns about the potential negative effect of the aged RAP binder on the field performance, especially cracking resistance, of high RAP mixtures. To address the concerns, there has been increasing interest in utilizing rejuvenators to improve the cracking performance of high RAP mixtures. The objective of this study was to determine the benefits of using a new rejuvenator made from renewable sources in asphalt mixtures with high RAP contents. The study was conducted by determining and comparing the laboratory performance properties of three mixtures and the binders extracted from the mixes. The three mixtures evaluated in this study included two 50% RAP mixtures (RAP binder ratio = 0.55) with and without the rejuvenator and a comparable virgin mix. Results of this study suggested that the new rejuvenator was effective in improving both the intermediate and low temperature cracking performance characteristics of the 50% RAP mix close to those of the virgin mix at the short-term laboratory aging condition without affecting its rutting and stripping resistance. It is recommended that a field study of this rejuvenator be conducted to further evaluate its effect on the long-term field performance of high RAP mixes.
This study was conducted to address some of the New England state transportation agencies’ concerns associated with the use of Re-refined Engine Oil Bottoms (REOB) in asphalt binders and mixtures. The effects of REOB on the physical and rheological properties of an asphalt binder were investigated. This evaluation was completed after AASHTOspecified short-term and long-term aging and after extended long-term aging. Also, the effect of REOB modified binders on the performance of asphalt mixtures after short- and long-term aging was evaluated in terms of moisture damage, rutting, and cracking. Two straight run binders (PG 58-28 and PG 64-22), a typical PG 64-28, two sources of REOB, an aromatic oil, and PolyPhosphoric Acid (PPA) were utilized. The PG 64-22 was modified with each source of REOB separately to attain a PG 58-28. These modified PG 58-28 binders were compared to the straight run PG 58-28. The modified and the straight run PG 58-28 binders were further modified with PPA to attain a PG 64-28 which is commonly specified in the Northeast. This modified PG 64-28 was compared to a typical PG 64-28 that has been used in the past without REOB. This same binder modification to attain a PG 58-28 and PG 64-28 was repeated with the aromatic oil for comparison purposes.
Rheological results plotted on the Black Space and wo—R-value Space diagrams showed that the addition of REOB to attain the PG 58-28 caused the binders to age more relative to the straight run binder. The results also indicated that the use of higher dosages of REOB can cause increased binder aging.
Mixture moisture damage tests showed that REOB could result in mixture premature failure. The rutting tests indicated that generally the REOB did not cause the mixtures to fail. Cracking tests conducted at intermediate temperature on REOB-modified mixtures generally indicated a reduction in fracture energy, as compared to the straight run or typical binder counterpart. A flexibility index (FI) calculated from the same cracking test showed that the aromatic oil modified mixtures generally had a higher value than the REOB modified mixtures suggesting less susceptibility to cracking. Interaction plots developed using the FI and Hamburg test results revealed significant differences among mixes with various binder formulations and the effects of long-term aging on the interaction plots were evident. Low temperature cracking evaluations detected minor effects on low-temperature fracture properties associated with various combinations of REOB tested. Performance space diagrams indicated that the REOB modified mixtures remained within the passing zone in a Hamburg Wheel Tracking-Disc Shaped Compact Tension DC(T) tests diagram for low to medium traffic level.
Overall, the particular mixture tests used in this study did not provide evidence that using REOB decreases performance. The performance data collected by using the two REOB sources varied by the particular test, and sometimes by the type of REOB or by the PG of the binder. The use of aromatic oil did not show this variability and the results generally indicated good performance. The variability of the data when REOB was used underscores the importance of thoroughly testing REOB modified binder and mixture for performance. Finally, other important issues like dosage and consistency of REOB are still currently being investigated.
Papers were presented on a wide variety of subject matter including: Environmental Evaluation of Road Projects; Innovative Road Management Arrangements; Funding of Road Infrastructure; Shadow and Direct User Toll (PPP); Economic Aspects of Mobility Pricing; New Approaches to Appraisal of Social Impacts of Road Projects; Sustainable Maintenance of Rural Roads; Project Governance and Institutional Integrity; Capturing and Understanding Customer Needs; Human Resources for the Future; Management of Roads; Keeping Cities Moving; Freight Transport; Winter Service in Latin America; Linear Settlements: the World-Wide Disaster for Road Safety; Methods for Road Safety Impact Assessments; Road Safety System Approach; The System Approach of Human Factors in Road Design and Operations; Managing Operational Risk in the Road Sector; Sustainable Approaches for Road Tunnels; Adaptation of Road Pavements to Climate Change; Innovation in Road Pavements; Road Bridges; Innovations in the Treatment and Use of Marginal Local Materials; Innovations in Construction and Maintenance of Unpaved Roads in Developing Countries.
Merci à nos commanditaires premier
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