Over the past two decades, roadways in several residential neighborhoods within northeast Edmonton have experienced significant early structural failures. Failures were so severe in some cases that heavy vehicles (i.e. garbage and fire trucks) were not able to access some affected streets. These failures occurred as a result of the presence of subgrade soils that are susceptible to water softening, poor subgrade drainage, and additional water drainage from private sump pumps. As a consequence, The City of Edmonton has established an extensive roads program that conducts annual replacement of roadways in northeast Edmonton.
As part of the above-noted roads replacement program, two trial sections were selected by The City of Edmonton to be reconstructed in 2009. These sections were located in adjacent cul-de-sacs to provide for comparison of performance between two constructions methods. One section was constructed using a traditional granular section, and the other used lightweight cellular concrete (LCC) as a subbase material. LCC is a construction material formed by mixing a cement and water slurry with a pre-formed foam, similar in consistency to shaving cream. The material is produced onsite and pumped into place using proprietary pumping equipment that may be setup several hundred meters from the pour area. The LCC supplied for the above-noted projects had a wet (cast) density of 475 kg/m3, which is approximately one-fifth the density of typical granular subbase. As a result of the high percentage of air bubbles (approximately 72% by volume), the material also has insulating qualities that, depending on the applied thickness, can reduce or prevent frost heave and subsequent thaw weakening of subgrade soils.
Load-deflection data was gathered on the trial sections for both pre and post construction conditions using The City of Edmonton’s Dynaflect system. The City performed additional testing in 2016 using both its Dynaflect and Falling Weight Deflectometer systems. The results of this testing are presented in this paper. Since reconstruction, no maintenance activities have been required for either the granular or cellular concrete trial sections.
Le ministère des Transports, de la Mobilité durable et de l’Électrification des transports entretient un vaste réseau routier durant la période hivernale. À l’exception du réseau local (107 000 km), dont la responsabilité incombe aux municipalités du Québec, les routes relevant de la compétence du Ministère représentent près de 31 000 km.
Ce réseau est entretenu en grande partie par le secteur privé (66 %) alors que la portion restante est répartie entre les équipes opérationnelles du Ministère (20 %) et les municipalités (14 %).
Durant la saison froide, quelque 800 000 tonnes de sel de voirie sont épandues annuellement sur le réseau du Ministère, occasionnant des effets préjudiciables à la flore, à la faune, à la qualité de l’eau, aux sols et aux infrastructures à des degrés divers. Au Québec, le suivi de la qualité de l’eau de plusieurs lacs en périphérie urbaine démontre que, dans certains cas, les concentrations en chlorure augmentent de façon continue. Pour de plus rares cas, les concentrations dépassent même le seuil de toxicité chronique pour la vie aquatique.
Considérant que le chlorure de sodium a des impacts documentés sur l’environnement et les infrastructures routières, il apparaît primordial d’en faire une utilisation et une gestion responsables.
Visual inspection is the state-of-practice in deciding the type and location of repairs in road rehabilitation projects. Field non-destructive testing (NDT) can provide information on pavements performance to help make such decisions. NDT was carried out on City of Winnipeg’s regional roads. The projects included two rigid pavements and one composite structure and they were scheduled for rehabilitation in 2017.
Falling Weight Deflectometer (FWD) testing was performed prior to and after milling and full-depth repairs to evaluate the effect of the asphalt overlay on load transfer efficiency, as well as the improvement in joint performance achieved by full-depth repairs. Real Time Kinematic (RTK) surveying equipment was used to capture coordinates of test locations for retesting after milling or full-depth repairs. This study also evaluates how pavement deflection measurements can be incorporated at the design stage to facilitate the decision making process and to optimize rehabilitation costs with the availability of joint performance information.
Hundred fifty joints were tested in total and their performance was evaluated through their load transfer efficiency, peak deflection and differential deflection between the approach and leave slabs at the joint. It was found that load transfer efficiency measurement experienced a considerable reduction once the asphalt overlay was milled. This means that testing concrete joints performance before milling overestimates their performance and could lead to different repair decisions. Joints generally achieved over 90% load transfer efficiency following a full-depth repair. In cases where the load transfer efficiency was low after a full-depth repair, the peak and differential deflections were found to be small. This highlights the importance of including peak and differential deflection criteria in evaluating performance. Moreover, it was found that in one project approximately 22% of tested joints were under-performing in terms of load transfer efficiency, while 50% of them received full-depth repair. The cost of such repair could have been optimized with the availability of such information. This study sheds light on the benefits of FWD information in the decision making process of joint repairs.
Traditionally, road assets are monitored and inventory controlled getting direct access to each asset, which can be very time-consuming and requires numerous field recordings and trained personnel. With recent advancements in data collection technologies, vehicle-based data collection platforms can collect millions of data points from all spatial directions at highway speed per second. The big data incorporates LiDAR point clouds, 360o degree imagery, and Laser Crack Measurement Sensor data. This paper presents the development of an innovative advanced machine learning algorithm capable of extracting roadside assets including traffic signs, guardrails, line painting, and rumble strips from the big database. The machine learning process starts with training steps in which hundreds of thousands of training datasets are used and then tested against the testing dataset. Once the testing database has passed at 99% or more, the trained program is ready to detect that asset. The techniques used to train machine learning algorithms to extract signs from the LiDAR database are developed using unsupervised clustering algorithm followed by auto-classification using machine learning classifiers with imagery. A similar approach has been taken to identify other assets such as guardrails, rumble strips, and line paintings. This process has been able to successfully identify and classify traffic signs from highways as well as urban and rural roads. The developed machine learning algorithm is programmed in parallel and performed at typical highway operation speed. Additional information about the geometry and retro-reflectivity properties are other important features that are also calculated and reported by this algorithm. The developed algorithm has been in production phase in the British Columbia Ministry of Transportations Asset Management project, in more than 13000 km of highways and has been able to pass all quality assurance mechanisms. This paper outlines the steps followed to develop a roadside asset extraction machine learning algorithm from the LiDAR and imagery database, as well as present a sample of the resultant roadway traffic sign asset database.
Over the past few years there has been extensive innovation in Geospatial technologies that can be used in revolutionary new ways in order to accurately and efficiently map and assess transportation assets. Significant investments in R&D and the race amongst auto manufacturers towards making connected and autonomous vehicles a reality has been instrumental in facilitating a rapid evolution of how spatial data is collected, processed and turned into usable intelligent transportation asset information.
There are a number of sensors and information systems that transportation asset managers can leverage in order to manage their assets. Amongst this plethora of technologies, both LiDAR and Imaging provide some of the most important and accurate foundational mapping information regarding the assets and features in the transportation sector.
Advanced sensor technologies in combination with artificial intelligence, machine learning and integrated information systems provide significant opportunities for improvements and efficiencies in the collection of data as it relates to transportation asset management.
This presentation will discuss some of the differences between LiDAR and Imaging, some of the different systems that are being used to collect these different types of spatial data and how transportation asset information is accurately and effectively extracted and derived from each type of data that these respective technologies produce.
The workforce is changing. Thoughtful work is being done around succession planning in our ministry and throughout government – this has led to a deliberate and planned approach to addressing changes. The Ministry of Transportation and Infrastructure has developed an action oriented Succession Committee with a Vision to “Motivate.Transfer.Transform.: Building talent for the future.” The mandate of the committee is to build a culture of shared responsibility for succession by influencing our organization to recruit, develop and retain a strong and diverse team within the BC public service.
As part of the ministry’s ongoing succession initiatives, it is critical that we continue to empower and provide our people with the resources and skills to be a resilient workforce for the future. To achieve this, one major element identified though employee consultation was leadership.
Tack coats are thin applications of asphalt emulsion between the layers of a pavement structure with the role of enhancing adhesion. Fog seals are thin emulsion applications to pavement surface for protecting the surface from oxidation and water ingress, as well as reducing the risk of raveling and stone loss. One of the downsides of using asphalt emulsions for these applications is the required breaking and curing time. Even after curing, traditional emulsion grades will track onto nearby surfaces. Slow curing fog seals require longer road closures and/or a light sand application before trafficking.
This paper presents the development stages of a non-tracking emulsion developed for bond coats and fog seals. The emulsion was formulated and engineered to be fast curing and provide a hard, non-tracking surface, suitable to support traffic without the use of sand application. Its tracking properties were assessed using novel tracking and curing tests, and its performance as a bond coat was measured using the tack coat shear test developed by McAsphalt. Trial projects of tack coating and fog seals were conducted from 2013 to 2016 throughout several Canadian provinces. Performance to date in the field, as well as some observed challenges, are presented.
Fatigue resistance is an important factor for high quality Hot Mix Asphalt (HMA). Asphalt cements containing higher concentrations of polymer are known to be more strain tolerant, which can provide improved fatigue resistance in HMA. Use of polymer modified asphalt cement is a proven way to improve fatigue performance.
Many municipalities and the Ontario Ministry of Transportation have implemented the Double Edge Notched Tension (DENT) test to improve the fatigue performance of the asphalt cement and the corresponding HMA. The DENT test is performed at an intermediate temperature that should correspond with fatigue performance. The Multiple Stress Creep Recovery (MSCR) test is an environmental test that measures the compliance and elastic response of an asphalt binder. The MSCR test is conducted at the high-performance grade temperature based on the local 7-day maximum temperature.
The results from this research have shown that there is no clear relationship between increasing concentration of polymer modification and DENT performance. On the other hand, the percent recovery showed a very good correlation with polymer modification and performance. Based on the information presented in this paper, the MSCR is ultimately expected to be validated by HMA fatigue testing while the DENT is not.
The Development of Crash Modification Factors program conducted the safety evaluation of red-light indicator lights (RLILs) at intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated safety effectiveness of RLILs. RLILs are auxiliary lights mounted on signal heads, mast arms, or poles that are directly connected to a traffic-control signal. The RLIL activates at the onset of the red phase and allows an enforcement officer to observe red-light running from downstream of the intersection. This strategy is intended to reduce the frequency of crashes resulting from drivers disobeying traffic signals by providing a safer and more efficient means for police to enforce the red interval. Geometric, traffic, and crash data were obtained at treated four-legged signalized intersections in Florida. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before–after analysis was conducted using reference groups of untreated four-legged signalized intersections with characteristics similar to those of the treated sites. The analysis also controlled for changes in traffic volumes over time and time trends in crash counts unrelated to the treatment. Results indicate statistically significant crash reductions for most crash types. Disobeyed signal crashes had an estimated crash modification factor (CMF) of 0.71. Total crashes, fatal and injury crashes, right-angle, and left-turn crashes had estimated CMFs of 0.94, 0.86, 0.91, and 0.60, respectively. The benefit-cost ratio estimated with conservative cost and service life assumptions was 92:1 for four-legged signalized intersections. The results suggest that the treatment, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective. In addition to the crash-related benefits, RLILs can improve the efficiency and safety of red-light running enforcement efforts. While this study did not evaluate the efficiency and safety impacts with respect to enforcement, it should be noted that RLILs do allow police to observe violators from a downstream position, eliminating the need for a second observer (upstream) and the need to pursue a violator through the red light.
The authors of the original 2015 paper entitled “Cold Winter and Early Asphalt Pavement Cracking Observed in Ontario” would like to acknowledge the detailed response provided by Dr. Keith MacInnis, Senior Technical Advisor, Canadian Asphalt Industries, Hamilton, Ontario. We also appreciate that the above noted paper generated interest and discussion around this critical topic. The subject described in the paper was of great importance to the road owners, and the Canadian Technical Asphalt Association (CTAA) is the best forum for this kind of discussion.
This paper provides comments from the lead author of the paper in response to the comments that were provided by Dr. Keith MacInnis on the original 2015 paper.
Light Colour Asphalt Pavement (LCAP) is a process of designing and constructing asphalt pavements that meets the Leadership in Energy and Environmental Design (LEED) Solar Reflective Index (SRI) requirement that at a minimum 50 percent of the hardscape can be constructed using materials having an SRI value of 29 or higher. The purpose of the development of LCAP is to provide developers looking to achieve LEED certification with a paving alternative that provides performance that is equivalent to conventional asphalt pavement, but that will also meet the requirement of LEED. The LCAP process includes aggregate selection, asphalt mix modification, placement of asphalt mic, stripping of surface asphalt film from new pavement, and evaluation of reflectivity of aggregates, mixes, and in-place pavements.
The very light colour aggregate from Coco’s Badgley Island Quarry was identified as a suitable material for LCAP. Conventional new asphalt pavements have an SRI of about 0, and weathered asphalt pavements have an SRI of about 6. This paper describes the importance of LCAP technology in reducing the heat island effect, the benefits of using it, required testing, and practical development of a LCAP mix.
Over the past 25 years, Alberta Transportation (AT) has collected successive datasets of Falling Weight Deflectometer (FWD) deflection data over their 21,000 km (almost entirely flexible) highway network. A study was conducted to investigate the variation in back calculated subgrade modulus between two or more test dates in different collection years using AT’s FWD inventory data. Presently, AT uses the AASHTO 1993 method for the design of flexible pavement rehabilitation. The AASHTO 1993 design method only applies a temperature correction to the FWD central deflection, which is not directly used for estimated subgrade support strength, and therefore does not account for subgrade strength variation as a function of temperature at the time of testing.
This paper presents a subgrade modulus temperature correction model developed from the FWD inventory data. The model was able to reduce the variation of subgrade modulus by a statistically and practically significant amount. If implemented, the model can be incorporated into the pavement rehabilitation design method to either minimize the risk of an under-designed pavement from using a higher than typical back calculated subgrade modulus, or minimize the risk (added costs) of over-design from using lower than typical back calculated subgrade modulus.
TRB's E-Circular 232: Automated Vehicle Symposium 2017: Summary of a Symposium highlights the themes from an event that took place on July 11–13, 2017 in San Francisco, California. The report follows the general symposium agenda. The presentations by speakers in the general sessions are summarized, including the highlights from the 25 breakout sessions. A list of the posters presented in two sessions is provided. The appendices provide a description of the key topics covered in the breakout sessions.
This study evaluated the relative weights of rutting parameters based on the Hot Mix Asphalt (HMA) mixture’s rutting performance. Seven rutting parameters, each at two levels, were incorporated in an experimental matrix and investigated through a limestone mixture designed by Superpave method. Each mixture’s rutting performance for different combinations of parameters included in the designed matrix was determined in the laboratory using an Asphalt Pavement Analyzer (APA). The test results were analyzed with the matrix of rutting parameters employing a statistical approach.
The results showed that binder Performance Grade (PG), sample type, test temperature, and moisture are the most significant parameters to affect a HMA mixture’s rutting performance. Wheel load, hose pressure and percentage asphalt content at their chosen levels were shown to be less significant compared to the other parameters. A prediction of average rut depth under the influence of aforementioned significant factors at their defined level was performed. A range or spread in rut data for the predicted rut depth was also determined. The predicted range was verified by additional experiments. This research described a procedure to design an experimental matrix and developed a statistical procedure for analyzing such matrix parameters and test results.
Hot Mix Asphalt properties from lab-produced and plant-produced materials can vary significantly. Proportioning of the components for an asphalt mix design is the first step in the process for Hot Mix Asphalt Production. The mix designer must develop the “recipe” for mixing aggregates, asphalt and air to produce a mixture that will meet the performance demands of the pavement.
It must be remembered, however, that the laboratory mix design is only a starting point for the mix production process. During production, it is necessary to adjust the Job Mix Formula (JMF) in order to meet volumetric properties of the in-place pavement. These adjustments are typically minor but quite important to ensure that the mix produced meets the volumetric properties required in the field.
This paper discusses ways to create the mix design that will result in a mix having appropriate flexibility to make JMF adjustments. Issues included in the paper are mixture volumetric controls, aggregate gradation and shape control, mix production control and mix adjustments.
The Superpave performance grade binder specification (AASHTO MP1), first introduced in 1993 as a product of the Strategic Highway Research Program, is the predominant method used to specify asphalt binders for highway use in North America today.
Since 1993 several research projects have been conducted to evaluate if the binder specification identifies the performance characteristics of polymer modified binders. The general conclusion from this research has been that they do not. Consequently, other tests, most of which are not performance related, but which merely indicate the presence of a modifier, have been added by many highway agencies.
This paper covers the work that is currently being conducted, by the US Federal Highway Administration under the guidance of the Transportation Research Board’s Superpave Binder Expert Task Group, to fill these gaps in the binder specification and make them truly performance related and blind to modification. Additionally a review of the current Superpave tests, procedures, and the data available from these tests is presented. Using existing tests a procedure, while not directly performance related, provides a great deal more information about the performance characteristics of polymer modified binders than any of the currently used Superpave Plus specifications.
The determination of the low-temperature behavior of asphalt binders has always been an Achillean heel of asphalt binder testing. For decades, the stiffness modulus at low temperature was measured in research laboratories, however, its practical use only began with the Superpave specification. Unfortunately, very soon it revealed itself as incapable of sufficiently describing the characteristics imparted on asphalt binders, especially by some types of polymers. Direct Tension Tests and the present Superpave MP1A parameter Tcritical greatly improve our capabilities to differentiate between the low temperature properties of different asphalt binders.
This paper deals with the low temperature performance of asphalt binders produced from different crude oils and manufactured by modification by different types of polymers. Low temperature behaviour of different asphalt binders as determined by a bending beam rheometer, direct tension testing and Tcritical are compared. The mechanisms of the improvement of low temperature behaviour of polymer modified asphalt binders (increased tensile strength, slow stress growth with the decrease of temperature, better low temperature properties of base asphalt binder) are demonstrated.
The relationship between the glass transition temperature of the SBS polymer, the EBA polymer the EVA polymer and the low-temperature performance of the polymer-modified asphalt are discussed.
Micro-trenching, an innovative method for fiber optic cables installation, involves creating a narrow trench in the road pavement to place a cable or conduit; the trench is normally narrower than 40 mm wide and shallower than 300 mm deep, depending on the size of the used conduit and trencher. After cutting the pavement, the next step is cleaning the area and placing the cable or conduit inside the trench, followed by backfilling. The quality of the backfilling plays an important role in both the sustainability of the installed cable or conduit and the cut pavement; using unsuitable materials or improperly installing cable or conduit can significantly decrease pavement life. The trench dimensions are very small, so for a successful procedure the backfilling material should be self-compacted and flowable enough to penetrate and completely fill the whole trench depth. As it has been investigated before, using traditional backfilling material such as play sand is not appropriate for Canadian cold regions; hence, it is recommended to stabilize the conduit inside the pavement’s granular layer using a material similar to a cement grout. Alternatively, foam grout is a mixture of cement, water, and pre-formed foam; the foam considerably reduces the density of the blend by adding air, which consists of more than 25% of the mix. As a result, using this foam grout technology reduces the amount of cement required significantly and could be a cost effective solution for backfilling. The objective of this paper is to assess foam grout as a backfilling material for micro-trenching in cold climates. For this purpose, foam grout samples were prepared in a laboratory and their compressive strengths before and after several freeze and thaw cycles were investigated. Different mix-proportioning ratios were also studied in an attempt to create a more reliable method and assess variations in compressive strength and cost along with density.
In North America, chemical stabilizer that is commonly used in the full-depth reclamation process is General Use (GU) cement. Blended cements that contain substantial amount of supplementary cementitious materials, however, could be plausible alternatives that can help reduce the carbon footprint and improve certain properties, like shrinkage, of the stabilized materials. In this paper, the effects of blended cements, also known as Hydraulic Road Binder (HRB), on the strength and durability of full-depth reclaimed pavement materials were assessed based on laboratory investigations. The assessment was conducted using two types of reclaimed pavement materials and three types of blended cements. In addition, GU cement was used to produce control mixes. The strength of the stabilized materials was evaluated using unconfined compressive strength (UCS) test. The UCS test was performed on compacted specimens that had been prepared with different binder contents and moist cured for 7-days and 28-days. The durability assessment was carried out with freeze-thaw test. This test was done on compacted specimens that had been made with optimum binder contents. The results of UCS and freeze thaw tests were analyzed with ANOVA, Fisher’s test and Dunnett’s test to identify the effects of the blended cements on the strength and durability of the full-depth reclaimed pavement materials. The analyses outputs indicated that blended cements can provide equivalent or even better strength and durability than GU cement if applied in full-depth reclamation process.
As part of the City of Winnipeg’s Northeast Exchange District Renewals project, WSP Canada Group Limited was contracted to redesign John Hirsch Place as a unique shared space roadway in Winnipeg. The project involved the reconstruction of John Hirsch Place in Winnipeg’s historic exchange district and redesigning the right of way to a curbless shared street based on the Dutch ‘Woonerf’ (living street) model, which involves traffic yielding to pedestrian activity and significant landscaping to enhance the pedestrian environment. The curbless design was used to avoid defining areas and boundaries that restrict pedestrian movement but rather allow pedestrians to move freely within the site. Limited parking within the roadway is available, and vehicles are slowed by traffic calming measures such as bollards, narrow path of travel, and limited sight distance to discourage a large volume of vehicle traffic and enhance pedestrian safety and environment. The project is notable for its links to the district’s cultural context, technical innovations, and quality of design.
Due to the broad and complex nature of the project, transportation engineers, land drainage engineers, and landscape architects collaborated to develop the Woonerf design and blend traditional roadway improvements with innovative drainage solutions and significant streetscaping and landscaping to effectively create a unique shared space that will provide an example for the feasibility of shared streets in Winnipeg in an effort to aid in future reconfigurations of roadways to shared spaces.
This paper highlights the key components from this project with a focus on Winnipeg’s first Woonerf roadway design and the Strata Cell soil retention system pilot project and the social and environmental benefits resulting from the project.
Merci à nos commanditaires premier
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