Increasing traffic loads and climate stressors are key drivers of the deterioration of asphalt concrete pavement. In response to these challenges, asphalt binder modification has gained prominence to improve both the mechanical and the rheological properties of the material. One notable application of asphalt binder modification is the use of nanomaterials, which are capable of altering the asphalt binder at the nanoscale, thereby improving rutting resistance, low-temperature cracking resistance, fatigue resistance, and healing. In this study, the use of nanoclays for binder modification is investigated in a laboratory setting, focusing on the self-healing behaviour of the binder. The healing potential of nanoclay-modified asphalt is assessed for two different organo-modified montmorillonites at 2 and 4 percent dosages. For this purpose, a two-piece healing test employing a Dynamic Shear Rheometer is used to measure the intrinsic healing behaviour of these binders compared to an unmodified binder. Meanwhile, the effectiveness of the high shear mixing is analyzed using a Scanning Electron Microscope. It is observed that the complex shear modulus is recovered sooner after cracking when nanoclay is added to the mixture. Overall, this research yields promising results regarding the use of organo-modified montmorillonites as a nanomodifier to reduce asphalt deterioration.
Premature failure of asphalt longitudinal construction joints continues to be a concern of roadway authorities throughout North America. In Canada, improving joint performance often ranks as a priority amongst roadway agencies. The key factor affecting joint performance is generally insufficient compaction (high air voids). If left unattended (i.e., with little or no maintenance), the joint issues will greatly impact the overall performance of the pavement. Infrared heaters that pre-heat the joint prior to paving the second lane have been successfully used for over twenty years and are becoming more common as a very effective method to improve joint density and performance. Independent studies have shown that using joint heaters provides lower in-place air voids and permeability, and ultimately improves the bond resulting in longer durability. The City of Hamilton has specified the use of infrared joint heaters since 2007 where maintaining a hot joint is not viable. In Alaska, Ground Penetrating Radar (GPR) is being evaluated in conjunction with joint heaters to verify joint density. This paper will provide an in-depth review of the construction issues associated with longitudinal joint construction. The review will include current use of infrared joint heaters, and the associated specifications along with observed performance improvements.
Canada has over 1.13 million kilometres of roads (two-lane equivalent), making it the seventh-largest road network in the world. Roads in Canada are managed primarily by four different jurisdictions:· federal authorities, provincial authorities, territorial authorities, and regional authorities. Federal authorities manage the federal highways and roads in national parks. Provincial and territorial authorities are responsible for managing provincial and territorial roads, respectively. Trans Canada highways are also managed exclusively by the provincial and territorial authorities, while regional authorities are responsible for managing local roads and streets in their respective region. Approximately 80 percent of public roads in Canada are governed by the regional authorities, which refer to cities, towns, and municipalities, making them the most important contributors to the Canadian road management system. To understand the pavement management practices at the regional level, a country-wide road management survey was conducted. The survey covered all the essential components of a pavement management system, such as road type, inventory information, road condition assessment system, treatment program, maintenance priority program, pavement performance prediction model, etc. Forty-one cities, towns, and municipalities from nine different provinces participated in this survey and yielded a tremendous amount of data to explain contemporary roadway management practices in Canada at the regional level.
This guide is intended for use by agencies in evaluating soil and material stabilization products being promoted by suppliers. It also identifies soil stabilization products and processes used across Canada and internationally, with a look at their optimal applications and performance when data is available. This guide considers soil stabilization to include both soil and material modification and stabilization activities. Modification of soil considers soil improvement during or shortly after mixing to improve engineering properties such as plasticity and moisture sensitivity, to help facilitate or expedite construction operations. Stabilization of soil, on the other hand, considers a chemical and/or mechanical treatment of a mass of soil to improve its shear strength and durability for inclusion in a pavement structure. This guide focuses on the stabilization of pavement structures for roadways including subgrades, aggregate layers, and full depth reclamation of asphalt, chip seal and granular roadways. The project included a thorough literature review of relevant products and processes across Canada and internationally. A detailed survey was also prepared and distributed to agencies, consultants and contractors to collect information on current stabilization practices and product evaluation procedures used across Canada and internationally. Suppliers of stabilization products were also surveyed to develop a database of current stabilization products and their use and performance.
It has been shown that Canada’s climate is warming at more than double the global rate , therefore, Canadian road infrastructure could be at risk if adaptation strategies are neglected. Key climatic parameters that govern the design and performance of flexible pavement may alter in the future, leading to different climatic loads on road structures, which in turn may result in reduced performance and shortened service life. To that end, this research aims to propose a methodology for the incorporation of climatic projected changes in the design of flexible pavement in Canada. To reach this goal, first, climate change projections over Canada will be evaluated and limitations of existing climatic data used for pavement structural design will be assessed; second, the impacts of climate change on pavement performance will be further discussed, followed by the introduction of a methodology to incorporate climate change predictions in pavement structural design; lastly, an example will be performed to illustrate the incorporation of the climate change parameters in the design procedure of AASHTO 93. The climatic inputs to be evaluated are temperature, precipitation, permafrost thawing, and freeze thaw cycles. This study aims not only to provide guidelines for flexible pavement design but also to raise public awareness by engaging government and stakeholders across the country.
Pavement engineers use strain calculations to estimate road structural layer thickness requirements for design, load equivalency analysis and life cycle performance prediction of flexible pavements. The primary strain calculations traditionally used have been peak tensile horizontal orthogonal strain at the bottom of the hot mix layer and vertical compressive orthogonal strain at the top of the subgrade. These idealized peak orthogonal strains have been used to correlate to the primary structural pavement failure modes of fatigue cracking and rutting, respectively. Over recent years heavy commercial trucks have evolved in larger configurations that apply higher strain states within pavement structures. The objective of this study was to use non-linear 3-D pavement numerical modeling to quantify volumetric strain responses within typical flexible pavement structures under modern commercial heavy truck multi-lane loadings. This study evaluated volumetric strain distributions in two pavement structures across four truck configurations under single and multi-truck/multi-lane field state loading scenarios. Trucks evaluated in this study included a 5-axle semi, 7-axle semi, 8-axle b-train, and a 9-axle semi. All trucks were modeled at maximum allowable legal load limits representative of typical highway jurisdiction heavy haul load limits. Based on the 3-D pavement analysis conducted, larger heavy truck configurations as well as multi-lane/multi-truck field state loading can significantly increase primary responses within a pavement structure. Vertical deflection profile and volumetric shear strain in the subgrade were found to be more sensitive under larger trucks and multi-truck/multi-lane pavement loading. Volumetric strain calculations provide the added ability to perform reliability analysis across specific pavement primary responses. This study shows how pavement engineers can use 3-D volumetric primary pavement response profiles across different material layer types under any field state load condition for structural pavement design, life cycle performance predictions, and improved life cycle asset structural performance prediction.
A roadway system is often the single largest financial investment for a public agency. Pavement is one of the most important assets in the infrastructure asset system. It is crucial to maintain pavement in good performing condition to ensure optimal and sustainable performance. However, accelerated pavement deterioration has been of great concern to many stakeholders and transportation agencies due to the amount of money spent every year to rehabilitate newly constructed roads and mitigate the accelerated degradation in pavement condition. Historical condition data, stored in Pavement Management Systems (PMS), are a valuable source of information that can be used to investigate premature cracking in pavement and identify causes of early failure. This paper presents a methodology to use PMS collected condition data to identify premature cracking in pavements. Historical data collected over twenty years for the City of Ottawa was used to evaluate the City’s roads performance over time. Historical construction data for major rehabilitation activities was extracted from the PMS database and linked to the historical condition data. Measured distresses were scaled, indexed and an automated procedure was established to identify scenarios of premature cracking incidents over the twenty years analysis period. Statistical analysis was conducted to compare different distress indices and identify trends and predominant crack types that are highly impacting pavement performance.
Driven by human influence, Canada’s climate has warmed and will warm further at a rate of double the global average. Climate change phenomenon, commonly known as ‘global warming’, is expected to cause irreversible temperature rise as well as other environmental anomalies that could affect transportation infrastructures. With continued growth in greenhouse gas (GHG) emissions in future, rising temperatures will have consequences on the short and long-term performance of the Jointed Plain Concrete Pavement (JPCP) systems. In this study, climate change impact on a typical JPCP structure was modeled using Pavement ME Design (PMED) software. The PMED modeling results were fed into a two-layer feed-forward network with sigmoid hidden neurons and linear output neurons. Results of this study indicated that the developed ANN models are effective and capable of accurately predicting the potential and relative impact of climate change on JPCP.
Senator Sid Buckwold Bridge or Idylwyld Bridge (the Bridge) Rehabilitation was one of the most complex capital bridge rehabilitation projects undertaken by the City of Saskatoon (the City). The complexity of the project mainly stemmed from the high volume of daily traffic, monumental importance of the structure and its surrounding, and the unknowns associated with the structural elements. As this bridge is one of the four primary crossings connecting the east and west of Saskatoon by crossing South Saskatchewan River, it was crucial to complete the project efficiently to reduce the negative economic impact. As a part of the rehabilitation, the two ramp structures were also serviced. For the purpose of this paper, the focus will be on the main structure. The paper will briefly go into all stages of the project while going into greater details for some of the unique or complex challenges and/or methods utilized by the consultant.
This paper presents the findings of pandemic scenario simulation within an activity-based travel demand forecasting model – shorter-term decisions simulator (SDS), which is currently implemented in Halifax, Canada. The study develops five pandemic scenarios within SDS, namely business-as-usual, lockdown, reopening phase-1, reopening phase-2, and reopening phase-3 focusing on the COVID-19 outbreak. These scenarios are developed utilizing multiple data sources such as Google’s COVID-19 Community Mobility Report. Utilizing the scenarios, SDS predicts changes in individuals’ activity-travel decisions during the COVID-19 pandemic. For example, the microsimulation results suggest a 47% reduction in activity participation during lockdown, which starts decreasing with the reopening phases. It is predicted that 81% people will participate in only two out-of-home activities a day during lockdown, however, people engage in more activities as the urban system begins reopening. Spatial distribution of activities illustrates lower mandatory activity participation in downtown areas during lockdown that gradually reduces until reopening phase-2, however, increases in reopening phase-3. The proportion of discretionary activities is predicted to increase significantly in adjacent suburban areas and South and North Ends of Halifax from lockdown to reopening phase-3. In the case of mode choice, results suggest that choice of auto mode during the lockdown scenario reduces by 46% compared to the business-as-usual scenario. It is predicted to increase by 13% during reopening phase-3. Proportion of non-shared travel for different activity-based tours is also predicted to increase from lockdown to reopening scenarios. Moreover, SDS predicts lower vehicle usage during pandemic compared to the baseline scenario, specifically subcompact vehicle allocation to different activity-based tours. The findings of this paper will help policymakers to develop essential policy interventions to be prepared for any further epidemic situation in future.
There exists two factors to assist in deciding whether or not a municipality should expect to have a roadway management system, these being population size and road network size. A large population tends to contribute more vehicles to the roads, which leads to frequent maintenance needs and therefore requires a road management system. Municipalities with large road networks may choose to follow a road management guideline to optimize their maintenance schedules. But, in some cases, municipalities with only a few kilometers of roadway can play a vital role in the provincial road network, especially when those roads link important destinations. So, a few pertinent questions arise. Do population size and road network length determine whether a municipality or town adopts a road management system? How do municipalities with small population size and shorter road networks manage their roads? What can be the most feasible way for those municipalities to manage their roads? To answer these questions, a province-wide municipality staff survey was conducted in Newfoundland and Labrador (NL), Canada. Most of the municipalities in this province are sparsely populated, and the internal road networks are very small. The survey was conducted to determine the condition of the roadway assets in these small municipalities, the resources available, and the requirements of roadwork by transportation departments to do in order to improve their roads. This project was not a government-funded project, and there was no incentive for the participants. Therefore, participation was completely voluntary. The results provide significant information about roadway asset conditions and management systems in the municipalities.
The purpose of this paper is to develop a school location choice model for post-secondary (PS) students in the Greater Toronto-Hamilton Area (GTHA). This analysis differs from previous PS school choice modelling in three respects. Firstly, the model is not representing the college choice process directly. Instead, this analysis is an exercise in matching students who have already made PS school choice decisions to their selected institutions. While there are many areas of overlap, an important difference is that household information reflects where students reside after having selected a college, and possibly, moving out from their parental homes. Secondly, this study primarily analyzes geographical patterns in school location choice for applications in travel demand modelling. An emphasis is placed on modelling the accessibility of each school location to each student, rather than predicting school selectivity or institution type. Thirdly, an RF classifier is implemented for the location choice problem, a novel approach in the field, and its utility is compared to that of the classic econometric approaches. Section 2 presents a brief literature review of relevant works in PS school location choice modelling in general, and in the GTHA specifically. Section 3 introduces the two modelling methods used in this study: random utility models and random forest models. Section 4 describes the two datasets used: the 2015 and 2019 StudentMoveTO (SMTO) surveys. Section 5 presents a logit mode choice model for the 2015 dataset, and Section 6 then presents the development of a school location choice for this dataset. Section 7 presents the development of a random forest model for the school location choice problem and Section 8 summarizes and discusses the main results for the 2015 modelling. Building on the 2015 analysis, Section 9 describes the development of location choice models for the 2019 dataset, and section 10 summarizing the key findings from this analysis. Finally, Section 11 concludes the paper with a brief discussion of possible directions for future work.
High-level and landmark type bridges have been found to pose as an opportunity for the vulnerable in society to die by falling which can have a significant impact on roadway users and the general public who witness such events. Typical bridge railings and parapets, while providing protection to the general public as users of bridges, do not provide sufficient protection against intentional falls from a structure. This paper outlines the planning, design, and construction of a means protection barrier system installed on the recently replaced Burgoyne Bridge in St. Catharines, Ontario, Canada. The Burgoyne Bridge replacement was completed in 2017 and spans over Twelve Mile Creek and Hwy 406. The 125m main span utilizes a tri-chord steel arch flanked by twin decks each supported by a single composite trapezoidal steel box girder. Each deck carries one lane of traffic, a bicycle lane, and a sidewalk and are separated with a median gap of 5.5m running the full length of the 333m long bridge. The barrier for the exterior edges of the bridge consists of a unique inclined cantilever aluminum pipe picket type barrier, while the gap between the bridge decks is protected by a stainless-steel mesh netting system. Both barriers utilize the existing pedestrian railing post anchorages in an effort to both minimize impacts to the existing structure as well as expedite construction and reduce costs and materials. While visually noticeable, both barriers were designed to be sympathetic to the overall architecture of the bridge with the aim to not detract from the overall presence of the structure. This paper will discuss the current state of practice across Canada and the Unites States while highlighting the design parameters and testing developed for this project to ensure its successful performance. In an effort to fully understand the performance during service of these barrier systems, wind tunnel testing and dynamic analysis of the barriers and structure were carried out for various wind loading conditions, resulting in the need for a damper solution to be utilized to reduce vibrations. This paper will also summarize the design decisions and lessons learned during the preliminary design through to construction of the Burgoyne Bridge means protection barrier system. These barriers present a unique solution harmonious to the overall architecture of the bridge with the expectation that they will provide reliable protection for the St. Catharines community and general public for many years to come.
Permeable interlocking concrete pavements (PICP) allow stormwater to infiltrate directly through aggregate-filled joints. The lack of proven cost-effective and practical approaches for permeability restoration prevents the wide-spread adoption of PICP systems in Canada (and North America). Novel and practical maintenance and operational methods, supported by scientifically-based proof of effectiveness, are needed. Better methods explicitly tailored for PICP is needed so that the required interval between maintenance events can be lengthened and thereby reducing overall lifecycle costs. The University of Toronto conducted this study at a PICP test pad, constructed in 2017, located at the Toronto and Region Conservation Authority’s (TRCA) Kortright Centre for Conservation in Vaughan, Ontario. The test pad included seven 3 m by 3 m (10 ft by 10 ft) PICP cells constructed with a generic grey concrete paver arranged in a herringbone pattern. A perforated pipe drained the PICP cells. Five test cells were clogged with street sweepings graded to match clogging sediments sampled from mature PICP parking lots within the Greater Toronto Area. The test cells were clogged over several weeks over the summer in 2017 through a controlled accelerated clogging procedure developed by UofT researchers. Surface infiltration capacity was measured following ASTM C1781 procedures, and restorative maintenance was considered required when mean surface infiltration measurements approached 250 mm/hr (10 in/hr) which is generally equivalent to a 98% overall reduction in original surface infiltration rates. Subsequently, each cell received restorative maintenance. Five different maintenance treatments were tested including a high pressurized-air and vacuum system, regenerative air street sweeping, power washing followed by vacuuming, vacuum street sweeping and waterless mechanical street sweeping. One test cell was clogged with a mixture of street sweeping and clayey soils and maintained with the high pressurized-air and vacuum system to explore the impact that cohesive sediments have on maintenance effectiveness. Finally, one test cell was treated with early and repeated maintenance with a regenerative air street sweeper.
This paper presents how transportation planning concepts are utilized in municipal climate action plans across Canada. There is currently a gap in the understanding of how different jurisdictions are addressing climate adaptions, and the findings of this study contribute to the understanding of climate change mitigation for practitioners, policy makers, and academics. It is critically important to develop this knowledge given the well-supported evidence that climate change is becoming exponentially more severe due to human activities and Canada’s commitment to address climate change through the Paris Agreement. The goals of this study are achieved by identifying relevant climate action plans through an environmental scan of municipal jurisdictions: Halifax, Montreal, Toronto, Winnipeg, Saskatoon, Calgary, Vancouver, Yellowknife, and Whitehorse. A thematic analysis is conducted on the plans to show the prevalence of the themes: (i) Active Transportation, (ii) Public Transportation, (iii) Vehicle Emissions, (iv) Shared Mobility, and (v) Transportation Infrastructure. The results identified by the thematic analysis include the average rate that a theme occurs in each climate action plan and a comparison between municipal and provincial jurisdictions. When compared to literature on climate change policy creation, the results provide insight into how the geopolitical landscape of Canada influences each jurisdictions approach to transportation planning as an intervention to climate change.
The relationship between vehicle operating speed levels and road safety (i.e., collision frequency) has been the focus of several research studies in recent years. However, more research is needed to understand the relationship between speed variability measures and safety. It is, in fact, important to understand whether vehicles travelling slower or faster than the mean speed of traffic are more often involved in collisions than vehicles travelling at a speed close to the mean speed. In this study, three speed variability measures based on field free-flow speeds collected for 150 residential urban segments in the City of Saskatoon (Canada) were estimated and their association to collision frequency was explored. The three speed variability measures considered were standard deviation, variance, and coefficient of variation of speeds. Along with speed data, other data related to roadway and traffic features of segments were included in the data collection process.
The design and evaluation of infrastructure, including transportation systems, is based on climatic loads, such as wind, snow, rain, ice accretion and temperature. Currently, the climatic parameters in the codes and guidelines that are used for design, operation, and maintenance of transportation infrastructure, such as highway bridges and pavements are based on historical observations of climatic parameters. These climatic design data, thus, do not represent the future climatic conditions under climate change. This can lead to higher risks of failure and service disruption, and higher costs of rehabilitation and replacement of infrastructure assets. Therefore, there is a need to generate future projections of climatic data taking into account climate change and implement them in the design and management of transportation systems to ensure their safety, serviceability, functionality, and durability and to avoid costly rehabilitation and strengthening, and to minimize the disruption of services. The selection and implementation of future climatic data in the design and management of transportation infrastructure is a challenging task. As a preliminary step, it is of essential importance to understand the implications of climate change for different types of transportation infrastructure systems to identify the potential risks that climate change can impose on them. In addition, it should be noted that changes in the future climatic data depend on several factors such as the climatic region, climate variable, climatic design value statistics, planning horizon, etc. Moreover, the future climatic conditions largely depend on the human-induced greenhouse gas emissions scenarios that are described by representative concentration pathways (RCPs), which yield different levels of changes in the climatic design data. The selection of an appropriate RCP emission scenario is also a challenging task. This study provides insights into the implications of climate change for transportation infrastructure systems performance, and challenges for implementation of future climatic data in the design and management of infrastructure systems. The future projections for a number of climatic design parameters at various locations across Canada are presented in order to illustrate the implications of climate change for transportation infrastructure systems.
A pavement’s structure gradually deteriorates due to repeated traffic load and environmental effects. These effects lead to distresses such as permanent deformation, fatigue cracking and thermal cracking. Granular base course stabilization using asphalt emulsion is one the most popular techniques to enhance the layer performance in order to achieve sufficient bearing capacity and resistance to pavement distresses. The major drawbacks of asphalt emulsion-stabilized base course, though, are its low early strength, long curing time, and low resistance to permanent deformation and moisture damage. To address these drawbacks, the asphalt emulsion-stabilized layer is usually modified with cement, which can improve its early strength and performance properties. However, using the cement makes the treated base course more prone to shrinkage cracking. Asphaltenes is a waste material derived from Alberta oil-sands with no significant use in the pavement industry. Asphaltenes is one of the polar fractions of asphalt binder, and its addition to asphalt binder has been found to have a considerable effect in increasing stiffness. In this context, the present study compares the impact of cement versus asphaltenes on the asphalt emulsion-stabilized base performance properties. For this purpose, different concentrations of cement and asphaltenes (1% and 2% per weight of total mixture) are added to asphalt mixtures, and the mechanical properties of the mixtures, including the low-temperature performance, are evaluated. It is concluded that both asphaltenes and cement are effective in improving a mixture’s strength and rutting resistance. However, cement-modified mixtures are found to be more prone to low-temperature cracking than are asphaltenes-modified mixtures.
The pavement base course has a significant impact on pavement long-term performance. One of the methods to improve pavement strength is stabilization of the base course with asphalt emulsion for an adequate response to traffic loading and weather condition. Regardless of the advantages of this method, asphalt emulsion stabilized materials usually suffer from low resistance to permanent deformation, and to overcome this problem, additives are added to the mixtures. Asphaltenes derived from Alberta oil-sands, which is a by-product of bitumen deasphalting process, could be used as an additive, and it is expected to enhance the mechanical properties of mixtures considering it to be a polar fraction of asphalt binder. This study investigates the application of asphaltenes-modified asphalt emulsion for stabilization of granular base aggregates. The effect of asphaltenes powder on the permanent deformation properties of the modified mixtures was studied through three different tests including Marshall stability and flow test, Hamburg Wheel-Tracking (HWT) and flow number tests. The test matrix included the samples with two asphaltenes contents (1 and 2% per total mix) for the same optimum emulsion content. The optimum emulsion content was found to be 3.7% according to the test matrix, while for asphaltenes, the optimum content was found to be 1%. According to the performance tests result, The Marshall stability test indicates that there is an increase of about 47.9% and 96.9% in stability values for 1% and 2% asphaltenes-modified mixtures, respectively. In addition, Marshall quotient and HWT test results indicate that modified mixtures are more resistant to rutting as compared to the unmodified mixtures. Rutting resistance index (RRI) increases about 140% for both asphaltenes contents. Flow number test results showed about an 81% decrease in deformation of modified samples in comparison to unmodified samples. Thus, the overall results show the resistance of asphaltenes-modified mixtures to permanent deformation was significantly greater than unmodified mixes.