The Hamburg Wheel Tracking (HWT) laboratory test uses loaded wheel(s) to apply a moving load on asphalt mixture specimens to simulate traffic loading on asphalt pavements. Given that different machines with various degrees of compliance with the current American Association of State Highway and Transportation Officials (AASHTO) T 324 requirements are used by highway agencies, this study aimed to assess the capabilities of commercially available and representative HWT equipment, and to evaluate different analysis and reporting methods for rutting and stripping performance assessment. After performing a comprehensive evaluation of devices from different vendors, considerable discrepancies on equipment capabilities and configurations were identified. The machines did not meet all the requirements set forth in AASHTO T 324 including those for the wheel position waveform, the temperature range, and the reporting parameters. Evaluation of existing analysis methods revealed significant inconsistencies among different methods and deficiencies in the specification. Recommended modifications to the machines and test method were provided.
Accurate determination of asphalt content and aggregate gradation is critical for controlling quality of asphalt mixtures during construction. Most state specifications require quantitative evaluation of the asphalt content of mixes as a criterion for acceptance. The ignition oven test procedure specified in American Association of State Highway and Transportation Officials (AASHTO) T 308 (Standard method of test for determining the asphalt binder content of Hot Mix Asphalt [HMA] by the ignition method) is required or allowed by most state departments of transportation (DOTs) for determining the asphalt content and aggregate gradation of asphalt mixtures. The ignition oven test specified in AASHTO T 308 procedure requires the determination of asphalt content correction factors for each asphalt mix and for each ignition oven used. However, in some instances when numerous asphalt mix designs and several ignition ovens are available, correction factors (CFs) are shared between ignition units, even when that practice is not allowed by the standard. There is a need to identify the consequences of sharing correction factors between units/mixes and also to identify testing parameters that affect the measured CFs. By identifying possible causes of variation, the test procedure could be adjusted to make the CFs more consistent between ignition ovens. Also, it should be possible to reduce the amount of difference in CFs between all types of equipment. A study was conducted to assess the variability of ignition oven CFs for different ignition oven unit brands and mixes to better understand the implications of sharing CFs. Twenty-three laboratories used various brands of ovens to test four mixes containing aggregates with varying CFs. The results indicated that CFs were significantly different for the different mixes even when the same unit brand was used. The within-lab and between-lab precision developed in this study suggests that different precision statements are necessary for aggregates with high breakdown potential and that the current precision included in AASHTO T 308 was likely developed for low weight loss aggregate making it unacceptable to use for aggregates with higher CFs. It was also found that the addition of lime caused no significant difference in the measured asphalt content when the CF was correctly measured. However, it was cautioned that a change in amount of lime during mixture production would affect the measured asphalt content. In addition, ways to minimise variability in asphalt CF were evaluated. It was determined that ignition tests conducted at lower temperature (427°C) proved to be effective in reducing the variability in measured asphalt content since the lower temperature reduced the asphalt correction factors for asphalt mixes.
Le présent code de bonne pratique décrit la mise en œuvre des enrobés bitumineux sur chantier, depuis la préparation des travaux jusqu'à l'ouverture de la route au trafic.
Pour commencer, le premier chapitre décrit en détail le matériel utilisé. Les camions, les répandeuses de liant, les finisseurs, les alimentateurs et les compacteurs y sont traités, afin que le lecteur puisse entamer les chapitres suivants en connaissance de cause.
La mise en place de l’enrobe doit être abordée comme il se doit : la préparation, tant administrative que logistique, est capitale pour la réussite du projet. L’organisation du transport est cruciale, car une alimentation uniforme et continue en enrobé est une condition fondamentale pour garantir un bon niveau de qualité.
Le chapitre 3 traite de l’exécution du chantier. Il débute par une description succincte du fraisage et de la pose de la couche de collage. La pose des enrobés au finisseur est ensuite décrite en détail; le comment et le pourquoi des principaux réglages de la machine y sont expliqués. Arrive ensuite le compactage de l’enrobé, où l’on insiste sur l’importance d’un compactage suffisant des couches dans un intervalle de température correct. Le code de bonne pratique donne par la suite quelques spécificités sur la mise en œuvre des différents types d’enrobés.
Le contrôle de la qualité pendant et après l’exécution des travaux est une étape importante du processus et est l’objet du chapitre 5. Le chapitre suivant aborde l’ouverture au trafic, et souligne l’importance du temps de refroidissement nécessaire avant que le trafic puisse circuler sur le revêtement neuf.
Enfin, s’ensuivent quelques points d’attention importants liés aux conditions météorologiques lors de travaux, à la planéité, à l’homogénéité et à la ségrégation, ainsi qu’à la rugosité.
Chip seals are among the most cost-effective surface treatments available for pavement preventive maintenance. However, frequent issues associated with asphalt emulsion early mechanical strength development, resulting in premature surface treatment failure, have led to the need to improve the characterisation of the chip seal curing process. As such, the use of an electrical resistance measurement has been studied to develop a sound construction methodology that prevents common failures that occur soon after construction. This paper presents a novel approach, based on electrical resistance measurements, to determine when a chip seal has developed enough binder adhesive strength to bond to the existing pavement while keeping the aggregate chips in place. The electrical resistance measurements provide a rapid, non-destructive indication of the amount of curing that has occurred. By implementing this methodology the user can determine when a chip seal has gained sufficient mechanical strength to allow for brooming or opening to unrestricted traffic without an undue loss of cover aggregate. Laboratory and full-scale field trials were conducted using a variety of materials. The electrical properties of the fresh seal coats were quantified by employing a handheld electrical device with a two-point probe resistance measurement. The experimental results suggest that chip seal systems have gained significant mechanical strength when the initial electrical resistance measurement increases by a factor of 10. As a result, this study establishes that electrical resistance measurements can be used to determine when a fresh chip seal has sufficiently cured to withstand the shear forces of brooms and uncontrolled traffic. The implementation of the technique could potentially impact chip seal construction quality, as well as service life performance.
Cracking is one of the most prevalent types of distresses in asphalt pavements. There are different cracking index parameters that are determined from tests conducted on binders and mixtures to assess cracking potential. The objective of this study is to compare binder and mixture parameters and evaluate the similarities and differences between the rankings and values obtained. This study includes binder and mixture testing on 14 plant-produced mixtures including 3 different binder grades, 3 binder sources, 3 aggregate gradations, and mixtures containing a range of reclaimed asphalt pavement and/or recycled asphalt shingles contents. Testing included PG grading and 4 mm dynamic shear rheometer testing on the extracted and recovered binders that were long-term aged. Mixture testing included complex modulus, simplified viscoelastic continuum damage (SVECD) fatigue, and disc-shaped compact tension testing on short-term-aged mixtures. Parameters evaluated included high and low performance grade (PG) temperatures, Tc , Glover–Rowe parameter (binder and mix-based), R value, dynamic modulus, phase angle, number of cycles to failure from SVECD and layered viscoelastic critical distresses analysis, and fracture energy. The results show that generally the binder parameters correlate well with each other but the mixture parameters do not. Good correlation was observed between binder and mixture stiffness-based parameters, but there was generally low correlation observed between binder and mixture cracking parameters for the mixtures evaluated in this study, possibly a result of differences in ageing level. Recommended future work includes non-linear statistical analysis, incorporation of field performance, and testing on long-term-aged mixtures.
During cold recycling, water is added to facilitate the dispersion of foamed asphalt in the mixture and to achieve uniform mixing and help compaction by providing sufficient lubrication. Too little water may cause difficulty in workability and compaction of the mixture, but too much water may extend the curing time and reduce density and strength. Therefore, the optimum water content (OWC) was considered as one of the most important factors in mix design procedures for cold recycling. Currently, mix design procedures for cold recycled foamed asphalt mixtures suggest adding water to the mixture at an optimum content to facilitate mixing and compaction. However, there is no standard method for determining the optimum total water content (OTWC) for cold recycling mixtures. Several empirical relationships were developed to determine the OTWC based on modified Proctor test results for Reclaimed Asphalt Pavement (RAP)/aggregate. However, the compaction effort in the modified Proctor test for RAP/aggregate may not match that for mixtures, which is compacted using the Superpave Gyratory Compactor (SGC) or Marshall hammer. A study is underway to improve the design method for cold recycled foamed asphalt mixtures with 100% reclaimed asphalt pavement (RAP). The purpose of this paper is to optimise the design procedure by developing a new method to determine OTWC. SGC was used to compact RAP instead of the modified Proctor test to match the compaction effort recommended for foamed asphalt mixtures. A regression model was developed to calculate the OTWC for a mixture based on the determined OWC of the RAP, foamed asphalt content, and binder type as factors. The method for determining OTWC for a mixture was validated using six different mixtures and was found to correlate well with the measured OTWC, even though two of six mixtures had underestimated OTWC due to different binder source. Further comparisons with other two OTWC determining methods showed the mixtures at the proposed OTWC had improvement in indirect tensile strength.
Reflective cracking is one of the major type of distresses associated with the use of asphalt concrete (AC) overlay for rehabilitating deteriorated asphalt pavements. This paper briefly describes the research efforts completed in Nevada to identify the best promising techniques to mitigate reflective cracking in AC overlays under Nevada’s climatic and materials’ conditions. The main outcome of the study was the development of a preliminary performance-based mix design specification for an experimental stress relief course (referred to as ESRC) to be placed between the AC overlay and the milled AC surface. Consequently, in summer of 2015, the Nevada Department of Transportation (NDOT) implemented the developed specification on a demonstration project on US 95 in southern Nevada. The project included test sections with three different strategies: (1) AC overlay on top of the ESRC mixture, (2) AC overlay on top of the NDOT fine-graded Type 3 mixture (SRC-T3), and (3) AC overlay without any stress relief layer. An extensive laboratory evaluation was conducted on all three mixtures using both laboratory-mixed laboratory-compacted and field-mixed laboratory-compacted mixtures. Core samples were also collected after construction and were evaluated for in-place thickness and air voids as well as resistance to reflective cracking. The data showed promising results for the ESRC mixture in terms of its resistance to fatigue and reflective cracking while maintaining an acceptable level of stability and resistance to rutting. A windshield survey conducted approximately 13 months after construction showed no distresses in any of the surveyed sections. In summary, the study showed a very good performance for the ESRC mixture thus far, making it a promising technique for reflective cracking mitigation in Nevada.
This paper describes the development and practical application of regression equations to estimate the relative load associated cracking resistance of asphalt mixtures from properties that are included in specifications and controlled through current quality control and acceptance procedures. This work was part of a research study performed through the Wisconsin Highway Research Program to evaluate changes to the composition of asphalt concrete mixtures that should be considered to improve the durability of flexible pavements. Based on the findings of a synthesis of current research, a laboratory experiment was conducted to quantify the effects of: (1) effective binder volume, (2) virgin binder low temperature performance grade, (3) recycled binder content, and (4) polymer modification on the resistance of typical Wisconsin mixtures to aging and load associated cracking. For the types of mixtures normally used in Wisconsin, the laboratory experiment found mixture composition had little effect on aging; however, load associated cracking resistance was significantly affected. The laboratory experiment produced a regression equation that was used to recommend revised volumetric criteria that provide equivalent load associated cracking resistance and allow producers the flexibility to design mixtures using a range of effective binder contents, recycled binder contents, and virgin binders.
Robustness refers to the ability of a road network to maintain its functionality intact when exposed to some perturbation. The concept of the Network Robustness Index (NRI) was explored by Scott et al (2006) and is defined as the difference in travel time on the road network between the existing condition and a simulated condition where the capacity of a link or segment is reduced or completely eliminated. Another previous work by Maoh et al (2012) examined the critical links along the Ontario major roads network and identified the segments that serve as the shortest path between the most origin-destination pairs. The work presented in this paper builds on these two previous studies and aims to examine the robustness of the critical segments of the Ontario trucking network, using a sensitivity analysis simulation approach. Six segments in particular were identified as the most critical, serving as the shortest paths between the largest number of origin and destination regions in the province of Ontario. Conditions that would be encountered with capacity and speed reductions due to roadworks were replicated and examined through a series of simulation models. A sensitivity analysis was undertaken for each of these critical segments, simulating increasing levels of capacity reductions. The NRI for the entire network, for each reduction scenario, was used as a measure to examine the robustness of Ontario’s major roads network.
WSP Parsons Brinckerhoff was hired by the Ministry of Transportation (MTO) to develop the Transport and Regional Economic Simulator of Ontario (TRESO), which is a passenger, freight and macroeconomic model covering the Province of Ontario with connections to the rest of the world. When complete, MTO staff will be able to use TRESO to evaluate a wide variety of policy, planning and investment scenarios that will affect major transportation corridors and systems across the entire province, as well as gateways to other North American locations. Commodity and freight modelling is a heavy emphasis within TRESO. Example scenarios of interest to MTO staff include the effects of: economic growth or decline, land-use changes (reflected by adding new firms within a region), changing use of E-commerce, changes to the rail and marine infrastructure and possible trade barriers on truck, rail and marine freight travel patterns.
This paper presents an overview of two TRESO components - the commodity flow model and the long-distance truck model. The paper describes their inputs, a brief and high-level description of their structure, and some preliminary model results.
In Canada, Monteiro (2011) estimated that private trucking could account for as much as 85% of urban and 75% of inter-provincial truck movements. Therefore there is a clear need to better understand the role of private trucking in Canada. In particular, this research will inform the redesign of Statistics Canada’s Trucking Commodity Origin Destination (TCOD) survey to include private trucking. Filling this data gap will also improve the information available to Transport Canada and other policy makers that are grappling with an understanding of how to facilitate better freight movement.
The paper begins with a selective review of literature on outsourcing in general and on the decision to operate own-account or private trucking specifically. Next, the data used for the analysis are presented along with some descriptive statistics. Then, a multivariate binary choice mode is specified in order to determine those factors statistically associated with the use of private trucking. Results from the model are examined in some detail before the paper concludes by pointing to future research needs.
The objective of this paper is to quantify the energy use and emissions related to the construction and operation of homes and transportation vehicles under a variety of scenarios, in the goal of defining the optimal development type and gaining a better understanding of the differences in sustainability between a few key scenarios. This work will enable urban planning policy recommendations to be made using local data on development types and likely outcomes.
Transit stop plays a very important role in improving transit system performance, maintaining traffic flow, passenger safety and security. In public transportation system, transit stops are the points which effect passenger perception towards transit system and can affect ridership. Till date, operational factors are given more importance; therefore, this paper discusses important passenger perception factors to be considered while planning a transit stop. Guidelines for street transit stop planning are available in several transit agency manuals and mathematical models. However, these guidelines do not report on every street transit factor, vary a lot from each other, and do not give rank-based factor list. Further, transit user opinion is also important to rank the amenities provided at transit stop. To answer these limitations, this paper report on expert and user opinion surveys, their population and sample size, instrument design, preliminary pilot survey findings and procedure for result analysis.
Technological advancements in the manufacturing of key Electric Vehicle (EV) components, especially the battery components, have renewed public’s interest in EV adoption. These advancements continue to improve the competitiveness of EV vehicles in terms of efficiency and ownership cost relative to gasoline-based vehicles. Governments around the globe are supporting policies that encourage the public as well as commercial entities to consider EV adoption on a more substantial scale. As such, governments and the private sector are responsible for the majority of global EV purchases as reported by Sierzchula (2014). Surprisingly, Canada’s global market share of EVs is only 0.4%. (IEA, 2017). This is significantly lower when compared to the European countries such as Norway which leads the globe with a share of 23.3% of global EV market (IEA, 2017).
This paper offers new insights on factors influencing the acquisition of EV fleets in Canada. An online survey was designed to collect information from a random sample of 1,008 Canadian businesses and organizations that own and operate fleets. The collected data included organization’s general characteristics, existing fleet characteristics, future acquisition plans and EV fleet prospects. Vehicle fleets were classified into three main types: Cars, Pickup Trucks and Utility Vehicles. The survey tries to identify and understand the factors influencing the preferences and motivations of government and commercial entities as they contemplate adopting EVs in their automobile, pickup truck and utility fleets. The collected data will help identify the circumstances that will lead to higher adoption rates of EVs by these entities.
This paper introduced a transit stop planning tool for evaluating the spacing, location, and design of existing/new transit stop(s) using a transit stop rating index. The rating index accounts for various transit stop planning factors along with their interdependencies and the uncertainty associated with their ranges. As opposed to pure mathematical fundamentals and concepts, the principles of Fuzzy Set Theory (FST) were used. To account for the variability in service planning standards and guidelines among different transit agencies, the developed tool provides transit planners with the flexibility to select relevant factors and change their ranges from a set of recommended default values. For illustration, a random transit stop was evaluated using the developed tool to demonstrate the applicability of tool in practical situations. However, the factor values used for this illustrative example is only assumption based and does not show the real data. Further, the socio-economic and demographic data and ridership data is confidential and is not used in this paper.
Although by implementation of new principles, tools, and techniques infrastructure asset management has been improved and expanded rapidly, however, key concerns resulted by new economic, and sustainability issues, still must be taken into account to develop a comprehensive framework for public transit system management. Existing researches focus more in case of system performance, and level of service while physical indicators are often selected for this purpose and user convenience criteria are ignored. It is also common to see limited budgets with some funds to palliative cosmetic solutions. Many cities face an enormous pressure to handle the ever-growing traffic demand with a limited budget. At the same time, demanding for quality, comfort, and safety by travelers is increasing makes it more complicated to deal with the challenge to convince costumers to abandon the use of private automobile.
The asset management of underground transit systems is a complex process as there are different types of facilities (rail cars, stations, tunnels, etc.) with completely different nature including many subcomponents geographically dispersed across a network. This leads to the need to use of a multi-facility multi-criteria assessment and decision making approach when it comes to the management of transit systems. The main objective of this study is to address recent issues should be covered by transit system management frameworks particularly focusing on subway systems to provide a safe, reliable and convenient service in the best interest of any metropolitan transit systems. Research proposes a framework to show how sub-models reflecting new issues could be attached to common transit agency approaches.
The EV market share has increased due to growing concern over environmental issues, financial incentives, and battery technology developments. Currently, EVs have sufficient driving range for intra-city trips where drivers can charge their vehicles at home or at the location of their activities. For inter-city travel, however, the trip distances are much longer and vehicles need to charge en-route to increase their driving range. Charging en-route is different from home-charging. Whereas in home-charging people can leave their vehicles plugged-in and come back later, en-route charging requires that drivers wait until the charging process is complete. Hence, it is critical to have fast chargers that cut down the charging time considerably and increase the charging coverage in order to promote EV penetration in the market. However, the high cost associated with constructing fast charging stations limits the number of charging stations that can be deployed and necessitates choosing their locations optimally.
In this study, we solve a nonlinear complementarity problem to optimize the location of fast charging stations to maximize network coverage and minimize total network travel time. Results show that optimizing the location of charging stations can reduce the total travel time by up to 21% whereas unregulated expansion of the charging infrastructure can actually increase the total network travel time.
Increase in daily travel activities coupled with reliance on conventional vehicles, places a significant pressure on the environment through tailpipe emissions. Fortunately, current advancements in battery technology along with the introduction of electric vehicles (EVs) is often considered as one of the more viable solutions to combating climate change and promoting sustainable energy. Due to the scarcity of EVs in the current market, many studies have utilized stated preference (SP) analysis along with estimating different forms of econometric model to identify and to understand factors affecting consumers’ choice decisions regarding new vehicle technologies (for example: Hackbarth & Madlener, 2016; Hoen & Koetse, 2014; Qian & Soopramanien, 2011). In addition, Potoglou and Kanaroglou (2008) provided a comprehensive literature review on various research methods regarding alternative fueled vehicle demand, focusing on SP analysis and different discrete choice models. Moreover, Rezvani, Jansson, & Bodin (2015) focused primarily on empirical studies evaluating various consumer behaviors towards plug-in electric vehicle adoption.
While most the existing studies have been concerned with household EV ownership, little has been done to explore the potential of adopting these emerging vehicle technologies by commercial fleets. Public and private organizations typically have high vehicle purchase rates (Dijk, Orsato, & Kemp, 2013) and high average annual mileage (Gnann, Plötz, Funke, & Wietschel, 2015), making them ideal EV adopters; thus, it is important to understand the motivations behind their EV acquisition decisions. Some of these motivations are firm-specific; government agency’s EV adoption is partly driven by restrictive legislations, while the potential profit increase through technological leadership encourages corporations’ EV purchasing decisions (Sierzchula, 2014). The analysis on this study is built on the extensive works regarding new vehicle technology ownership and extends their analyses on consumer rental context. As of 2015, the rental industry accounts for about 69% of all car registrations and approximately 47% of all light truck registrations, which are the highest in both categories (Canadian Automotive Fleet, 2016). The focus of this study is to determine and evaluate the preferences and motivations of Canadian consumers towards renting certain vehicle types using a SP survey.
Transit service reliability is one of the highly valued attributes for users and operators. This paper examines the impact on headway regularity and passenger loads in a simulated bus operation due to the bus capacity limits and the variability of departure headways. For the simulation purpose, four operational scenarios are set up. Same timetable and route characteristics are considered for all scenarios. In the first scenario, it is assumed that buses have infinite capacity and can accommodate all passengers waiting at bus stops. In other scenarios, bus capacity is constrained with different carrying capacities in order to analyze the impact of passengers being left behind when buses are full. The degree of dispatch headway also is varied to examine effects of headway regularity along the downstream of the route. Passengers arrival and dispatch headway of bus are assumed to follow Poisson and Gamma distribution respectively. Travel time between stops is assumed as constant in order to isolate the effect of dispatch headway variability. The simulation studies demonstrate the propagation of headway irregularity along the downstream of routes, a correlation between bus headways and passenger loading that caused bus bunching.
Merci à nos commanditaires premier
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