Saskatchewan’s Ministry of Highways and Infrastructure (SMHI) has replaced the visual assessment method for collecting pavement condition information with data measured using the Laser Crack Measuring System (LCMS). Pavement bleeding, stone pick outs, ravelling, wheel path rutting, bumps & dips and all types of pavement cracking have been incorporated into the Saskatchewan pavement asset management system. The paper discusses how the field calibration site and testing fit into the overall project. The site was set up to understand repeatability of the categorization and severity of each measured distress. The design, construction and results from the field calibration site are discussed. Analysis of multiple measurements taken at the site was used to modify and fine tune the metrics developed for the Pavement Asset Management System. The paper includes: An over view of the LCMS integration project; Design, set up and operation of a field calibration site for surface distress measured by the LCMS including cracking, bleeding, potholes, delamination, pick outs and ravelling; Findings from the analysis of the calibration testing; Improvements that will be incorporated into the next cycle of data collection.
The replacement of the actual Champlain Bridge crossing the Saint-Lawrence River at the height of Montréal and Brossard in the province of Quebec, Canada was tendered as a PPP project. The design of the new bridge required extensive geotechnical investigations in order to use construction techniques adapted to the timeline specified in the contract. Firstly, innovating investigation techniques that were used to determine the sound rock level for the installation of the pier foundation footings for the main bridge will be presented. Secondly, large scale in situ tests, using an Osterberg cell which were carried out to optimize the caissons design of the main tower will be described. Finally, the results of these investigations will be presented and the construction techniques put in place in order to allow quality control during construction of the foundations.
A major incident on a 400-series highway in the Greater Toronto Area has the potential to result in significant costs related to delay with respect to both passenger and commercial travel. Such incidents might involve collisions requiring police investigation or truck roll-overs, fires, or major spills, and could result in partial or full highway closures over multiple hours. In addition, significant delay would be anticipated on “diversion” routes used by drivers to circumvent the incident, as well as delay incurred during the system recovery period once the highway has been re-opened. Since traffic flows on major highways can range from 5,000 vehicles/hour to between 10,000 and 15,000 vehicles per hour over much of the typical day, the total delay cost from a single incident can run into the millions of dollars without even considering the implications for the broader economy. The Ministry of Transportation of Ontario (MTO) is in the process of reviewing response strategies to major incidents in two contexts. First, prior to the 2015 Pan Am/ParaPan Am Games, the Ministry developed traffic management plans to address major incidents affecting the highways accommodating the temporary High-Occupancy Vehicle (HOV) lanes implemented for the Games. These plans were designed to be more proactive than ambient incident response protocols. The use of the plans on several occasions during the Games created a generally favourable impression of the potential to reduce the impacts of traffic incidents. Secondly, the potential benefit associated with reducing the amount of time required to clear truck roll-overs and similar incidents has been investigated. We also note that ongoing expansion of the use of advanced traffic management systems (ATMS) by the Ministry enhances the toolbox available for incident-related traffic management. This paper describes the process used to develop more pro-active traffic management protocols for major incidents and provides an evaluation of some of the potential benefits of reducing the time required to clear truck roll-over incidents.
Longitudinal edge cracking is a widespread and costly safety concern for northern regulators, such as Yukon Highways and Public Works. The exact cause of longitudinal edge cracking in northern, low volume highways is not well understood. There are many factors that may be linked to cracking such as weak materials under the side slope toe, differential frost heave, oversteepened side slopes, concentration of moisture in road edge materials, and climate change. In an effort to prevent edge cracking in its low volume pavements, the Yukon Government partnered with FPInnovations and TenCate in 2015 and 2016 to construct two, instrumented, thin pavement test sites on the Campbell Highway near Watson Lake, Yukon. The test pavements were reinforced with a new geosynthetic product; instrumentation installed above and below the geotextile monitored roadbed moisture content and temperature. Mirafi® H2Ri is a high strength, woven, geotextile with hygroscopic, hydrophilic, and wicking properties that promote rapid drainage. It is anticipated that the geotextile will help prevent edge cracking by interrupting capillary rise from the subgrade, draining excess moisture from thawing layers, providing additional structural support, and confining road edge materials. Additional benefits may include the mitigation of rutting, cracking and pot holes associated with excess roadbed moisture. Activities in 2015 comprised site construction, and monitoring of moisture and temperature trends. The shoulders of the test pavement sections were consistently wetter than near centerline before and after paving. The geotextile, installed at the subbase-subgrade interface, reduced moisture in the subbase of both test pavements by up to 3%. In 2016, activities included continuing to evaluate roadbed moisture control by the geosynthetic, and assessing how well the new pavement design controls edge cracking and other pavement distresses. This innovative research will provide knowledge to owners, designers, and maintainers of low volume northern roads about road construction solutions to mitigate pavement distress, improve safety, and decrease maintenance costs.
Monitoring the temperature gradient of pavement structure layers and its effect on the structural behaviour helped to establish a fundamental understanding of the magnitude and impact of these variations on the pavement response to different loading conditions. The performance of pavements clearly reveals the need to properly measure the distribution of stresses and strains within road layers over a period of time taking into account the effect of extreme temperatures. The adverse effects of traffic speed during hot weather conditions on the structural behaviour of the flexible pavement are briefly discussed and possible recommendations to overcome these effects. Structural data including stresses and strains were collected under the action of external loads applied by a calibrated test trucks. To mimic the effect temperature extreme events on the flexible pavements, the study was carried out on flexible roads immediately after the construction at 51o C (truck impact test) and 44o C (truck creep test) and after one year at normal operating temperature (20o C). The field results showed unprecedented high stress and strain levels caused by low asphalt stiffness when the asphalt mat temperature is above a normal operating temperature. Traffic-induced stresses and strains transmitted through the asphalt concrete layer to unbound materials of the asphalt concrete are directly influenced by the stiffness. The impact test using a truck speed lower than 25 km/h resulted in a very high truck pressure impact. This study confirmed that most of pavement performance problems occurred at locations where buses frequently stopped and areas close to traffic signals. This finding highlighted the importance of traffic speed impact, extreme hot weather events and the interaction of both.
Canada’s first High Occupancy Toll (HOT) Lanes were a key government transportation commitment publicly announced in December 2015 and introduced to Ontario on September 15, 2016. The HOT pilot program and supporting retail and distribution system was developed and delivered in less than nine months as an online service. MTO and ServiceOntario collaborated to simultaneously develop policy, performance measures and program design, including an online digital retail service. This successful team approach ensured a key government priority was delivered within a compressed timeframe while introducing a new business model for digital services. Typically, to deploy an online service of this nature, it takes 12 to 18 months to deliver. The HOT Lanes Pilot Branch, Policy and Planning Division, Ministry of Transportation Ontario (MTO) is nominated for TAC’s Sustainable Urban Transportation Award for the development and implementation of Canada’s first High Occupancy Toll (HOT) Lane.
Located immediately east of Toronto, Ontario, the Regional Municipality of Durham includes 7 area municipalities with a total geographical area of approximately 2,590 square kilometres and a combined population of approximately 650,000 people. Situated in the highly developed and populated economic centre of Ontario, known as the Golden Horseshoe, Durham Region is expected to grow to an estimated population target of 970,000 by the year 2031. This growth will bring higher traffic volumes including buses and heavy trucks, which should be designed for in today’s road reconstruction projects. As part of its commitment to continually improve its service excellence, Durham Region is exploring innovative approaches to pavement design and road rehabilitation that could extend the life of its roadways and reduce overall lifecycle costs of the network. In line with this initiative, a pilot project was undertaken to reconstruct the intersection of Harwood Avenue and Bayly Street (Regional Road 22) in the Town of Ajax using a jointed plain concrete pavement design instead of a conventional asphalt pavement design. This paper provides an overview of the pilot project, highlighting key differences between concrete pavement design and traditional asphalt pavement design, and discusses construction considerations and lessons learned. This paper also outlines the construction staging that was followed and a traffic impact assessment undertaken by the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo.
Fourteen reclaimed asphalt pavement (RAP) mixtures designed with different combinations of RAP sources, contents (up to 40%) and mixture conditioning levels were evaluated to determine the maximum allowable amount of RAP material in surface courses without jeopardizing pavement cracking performance. Extracted RAP binder was blended with virgin polymer-modified asphalt (PMA) binder at various RAP binder replacement ratios. All blends behaved effectively as PMA binder as they met the multiple stress creep recovery (MSCR) % recovery requirement, and in addition they had satisfactory binder fracture energy density (FED) values. RAP gradation was found to significantly affect the fracture properties of RAP mixtures as it controls the distribution of RAP binder and potentially the degree of blending between virgin and RAP binder. Increased RAP content resulted in stronger (i.e., higher tensile strength) but more brittle (i.e., lower failure strain and lower mixture fracture energy) mixtures. However, after long-term oven aging (LTOA) plus cyclic pore pressure conditioning (CPPC) which was used to simulate long-term field aging conditioning, all RAP mixtures still exhibited dissipated creep strain energy to failure (DCSEf) values above 0.75 kJ/m3 and energy ratio (ER) values well above 1.0, indicating acceptable cracking performance. It must be emphasized that all RAP mixtures had good gradation characteristics as they all met Superpave design criteria and dominant aggregate size range and the interstitial component (DASR-IC) requirements. Therefore, satisfactory inclusion of up to 40% RAP was acceptable for well-designed PMA mixtures.
As the temperature of an asphalt pavement drops to below freezing point, the asphalt material starts to lose its ductility, and consequently, the asphalt mixture becomes more susceptible to cracking. The disk-shaped compact tension [DC(T)] fracture test has been used to quantify the fracture properties of asphalt concrete at subzero temperatures for more than a decade. The Asphalt Institute laboratory has successfully utilized the DC(T) test in several research studies. As a result of these studies, a valuable database has been gathered which represents the sensitivity of the DC(T) test, and exhibits how the test is capable of capturing the effects of various factors on the performance of asphalt mixtures at low temperatures. This paper briefly presents the findings from some of these studies. The paper presents the response of the DC(T) test to the variations in several factors relative to asphalt pavements including the crude source of the asphalt binder, aging of the asphalt mixture, deficiency in the in-place density, pavement temperature, using a warm-mix agent, using RAP and RAS materials, and chip sealing as a preservation method. The test proved to be well capable of capturing the variations in these factors; therefore, it can be utilized by pavement managers to assess changes in specimens from asphalt pavements over time to help determine if any maintenance or rehabilitation action is required. Furthermore, the test can be used to evaluate laboratory-made mixtures and ascertain if they would perform satisfactorily in their designated environmental conditions.
For current asphalt paving practice, many unconventional asphalt binders and additives have been introduced. Through physical and chemical interactions with base binders, these modifications usually affect the binder and mix strength and fracture properties as well as stiffness. However, the currently used binder grading system is based on the low temperature stiffness and relaxation behavior as measured using the Bending Beam Rheometer (BBR). The absence of strength and fracture properties in the asphalt binder grading process may result in inaccurate prediction of field performance. Five PG grade asphalt binders including unmodified, polyphosphoric acid (PPA) modified and styrene-butadiene-styrene (SBS) modified binders were tested using the BBR and the Asphalt Binder Cracking Device (ABCD). Asphalt mixes prepared with these five binders were also tested with a revised Asphalt Concrete Cracking Device (ACCD) test procedure. The test results showed improved strength and fracture resistance characteristics for SBS modified asphalt binders in the ABCD test and mixtures in the ACCD test, resulting in better performance than that predicted by the BBR low temperature PG grade. However, the PPA modified asphalt binder and the corresponding mixture exhibited worse performance in the ABCD and ACCD tests, respectively, than that predicted by the BBR low temperature PG grade, which may be attributed to the poor fracture resistance.
Low temperature cracking is a critical distress form and is heavily influenced by the relaxation and strength capabilities of the material. These properties are related to the stiffness through principles of viscoelasticity. Recently, there is elevated pressure on decisions made by pavement and materials engineers to produce the longest lasting, most resourceful pavement systems possible to optimize monetary and non-renewable resource usage. The primary objectives of this study are to: 1) assess the value of a parameter which can describe low temperature cracking resistance by using dynamic modulus ( E* ) and phase angle (delta) of the mixture and laboratory-measured performance; 2) present shape parameters of a mixture master curve that are directly related to the relaxation spectra, which is expected to play a pivotal role in low temperature distress resistance with aging; 3) define failure lines in Black Space which correspond with laboratory-measured performance and operate under a well-understood basis reinforced by the literature; and 4) provide agencies with a tool to aid in the movement towards a performance-based mixture design, acceptance, or rehabilitation decision-making system. An analysis of the mixture master curve is done to establish parameters which describe the relaxation spectra and aging potential of materials. A mixture-based Black Space parameter is presented based on results from the E* master curve construction and the thermal stress restrained specimen test. This approach holds promise, but must be calibrated with a robust database before serious implementation considerations are made. Future work will look to determine a common stiffness condition to better define the failure threshold and to identify possible alternatives to the modified Glover- Rowe function used in this study. Further evaluation is also needed to optimize the temperature-frequency combination of the Black Space parameter itself and ensure a condition is specified that can be captured by test equipment an owner agency or contractor may possess as part of a performance-based specification framework.
The development of the well-known Christensen-Anderson (CA) rheological model grew out of attempts to model the relaxation spectra of asphalt binders using a skewed logistic distribution function. For this reason, there are very strong relationships between the CA model parameters and the characteristics of relaxation spectra for asphalt binders. This paper presents a recently developed equation that allows direct and accurate calculation of the relaxation spectra from CA model parameters, demonstrating the nature of this relationship. Of the CA model/spectrum parameters, the most important in terms of describing overall behavior and potential performance is the R-value, which describes the shape and skewness of the spectrum. This parameter and other similar rheological parameters have been linked to various important aspects of asphalt binder behavior, including fatigue resistance, chemical composition and degree of oxidative aging. This makes the parameter R a potentially useful parameter for inclusion in asphalt binder specifications; although care must be taken in how it is determined to ensure that it is accurate, repeatable and reflects the performance characteristics of interest.
The determination of the rheological properties of the aged binder in reclaimed asphalt pavement (RAP) materials is a challenging problem. Conventionally, extraction and recovery are used to obtain the RAP binder for further experimental characterization; however, this procedure is not entirely reliable and accurate. Alternative and more precise approaches are based on asphalt mixture tests in combination with complex and sophisticated back-calculation methods which are costly and time consuming. In this paper a new and simple approach to estimate the rheological properties of RAP binder at intermediate temperature is proposed. This is based on Dynamic Shear Rheometer (DSR) tests performed on mortars, composed of a selected fine fraction of RAP and virgin binder, together with a new back-calculation solution. The properties of the bituminous blend of virgin and RAP binders are obtained through the manipulation of the Nielsen model equation to take into account the effects of frequency and temperature on mortar stiffness. The Voigt model is then used to estimate the complex modulus and the phase angle of the RAP binder from the complex modulus and the phase angle of the back-calculated binder blend.
This paper presents a simple, yet powerful method for simultaneously evaluating the high and low temperature performance of asphalt paving mixtures for the purpose of mixture design, evaluation, and forensic investigation. A performance-space diagram approach is described, with an emphasis on Hamburg-DC(T) plots presented in this paper. Specifically, a plot of Hamburg wheel tracking results, plotted in reverse order on the y-axis using an arithmetic scale, along with DC(T) fracture energy results, plotted on the x-axis, constitutes the Hamburg-DC(T) plot. Plotting candidate mixture designs, research results, etc., yields a surprising amount of insight towards mixture variables that affect overall performance. For instance, substitution of one straight-run binder grade for another results in a clear, predictable trade-off in the Hamburg-DC(T) performance space. Polymer modified grades, on the other hand, provide a more beneficial shift in the Hamburg-DC(T) space. The benefits of using this approach in the design of mixtures containing recycled asphalt mixture and recycled asphalt shingles are also presented. Effects of rejuvenators and the benefits of stone mastic asphalt designs are also demonstrated. Finally, a broad look at a large database of mixtures recently designed in Illinois is presented.
Mechanically stabilized earth (MSE) walls are a mature earth retention technology but concerns sometimes arise over who retains ultimate responsibility for wall design, quality assurance, asset management and repairs, and post-construction in-service monitoring, particularly if significant construction or performance problems occur. This guide provides owners, engineers, suppliers and contractors of MSE walls with practical guidance on the selection, design, construction, and inspection of these structures with a focus on public works projects. The guide was developed through reviews of published literature supplemented by a survey of industry stakeholders. It is not intended to reproduce the large volume of published design guidance and related information; rather the guide highlights aspects of the current state of practice in Canada and suggests modifications of current practice where deficiencies are apparent.
Ce Guide est une synthèse de pratiques canadiennes en matière de conception et de gestion des chaussées. Il offre un exposé théorique des enjeux, un résumé des meilleures pratiques et vise à être applicable partout au Canada, quelles que soient les conditions et l’administration routière. Il contient également des outils de gestion des actifs d'infrastructure de transport. Le Guide porte une attention particulière sur l'entretien courant et sur la préservation en tant que volets importants de la gestion des chaussées. Il attire l'attention sur les enjeux principaux touchant la durabilité, les changements climatiques. les innovations, ainsi que la conception et la gestion des routes à faible débit. Le Guide souligne explicitement les pratiques provinciales en plus des pratiques municipales.Il s'appuie sur l’expérience, mais tient également compte des besoins de l'avenir. Le document est un guide plutôt qu’un manuel détaillé de conception et chacun de ses quinze chapitres offre de nombreuses ressources additionnelles en tant que références futures. Le Guide est destiné à divers utilisateurs, praticiens et gestionnaires. Les utilisateurs universitaires en feront un précieux document de référence Les acteurs du secteur privé et public s'en serviront comme un outil de conception et de gestion pour la formation des nouveaux techniciens, ingénieurs et gestionnaires.
The Complete Street is rapidly being accepted and implemented in municipalities throughout the world to create a more inclusive and safe environment for all road users. The inability of many existing corridors to safely transport vulnerable road users to and from significant generators, while ensuring a road is also seen as a destination in and of itself, is an ongoing challenge municipalities face. Promoting the economic vibrancy of a corridor and the adjacent land uses through implementation of a safe, pedestrian-friendly, and aesthetically inviting corridor is quickly becoming a priority for many municipalities as antiquated design practices are superseded with new guidelines. This paper explores a real-world example of applied design principles employed to enhance road safety within an urban setting through exploration of a case study. The case study project area will be reviewed to identify why the specific corridor and surrounding area was identified for conversion to a Complete Street/Grand Boulevard. Complete Street design recommendations and best practices will be reviewed prior to exploring which key components were applied to the specific case study. An emphasis will be placed on the case study’s connectivity of a major transit hub to a significant shopping centre facility as well as the specific corridor enhancements applied to prioritize safe and efficient movement of vulnerable road users. A review of the custom roadway geometrics utilized to strike a balance between road safety, traffic operations, pedestrian accessibility, active modes, and transit will be explored. Applicable design standards and guidelines referenced during the design of the case study project will be reviewed and Complete Street design principles that were modified or compromised during design and construction will be discussed. The paper will examine the challenges of implementing Complete Streets design principles which often employ customized geometrics and do not necessarily correlate with historically approved best practices and design guidelines. From concept development to construction, the review and approval process will be explored to highlight some of the design compromises that were made to reach a balanced end product. The strategy for effective design and implementation of an urban corridor retrofit project will be presented with a breakdown of fundamental and applicable Complete Street best practices to create a safe and inviting experience for all road users.
Traffic calming measures continue to be effective ways of re-designing our roads to reduce speeds, increase yielding, and improve safety in our urban areas. The processes to implement traffic calming, however, can be long and arduous due to the many obstacles to permanent construction. In many cases the obstacles to implementation of traffic calming result in large delays during which time there are on-going safety concerns or collisions in many cases. These obstacles include funding, utilities, drainage and public support, to name a few. To overcome some of these obstacles the City of Calgary developed a pre-cast concrete shape, called Traffic Calming Curbs (TC Curbs) that allow modular creation of common traffic calming features that can be deployed quickly, at a low cost, and with a high degree of flexibility. The innovative process to design and construct the TC Curbs is described as well as process considerations for implementing their placement and lessons learned so far regarding their use. Case studies of TC Curb placement are examined including geometric design, placement, winter operations, and supporting traffic control. More importantly, evaluations of changes in motorist behaviours such as speed and yielding behaviour, and perceptions of various stakeholders are presented. Initial indications are that TC Curbs are a useful and effective tool to implement traffic calming as either an interim or potentially long term solution.
Comparing Level of Service (LOS) across infrastructure asset classes is difficult because of a lack of a common asset condition indicator. Some expert practitioners have suggested various types of asset value index as a common measure for comparing asset health but such an index, on its own, might mask the underlying level of service. In addition, quantifying risk and reliability is becoming ever more important when managing infrastructure assets. Asset Condition Indices are often composites of several measured or estimated asset attributes. Pavement Condition Indices, for example, are often derived by deducting values representing many different pavement distresses from a perfect score. However, when a composite index is used, the underlying nature of the severity of distress or its extent is not evident directly from the index. One must refer to the underlying individual distress data to determine why the index got its ultimate value. The magnitude of the deduct values are often somewhat subjective based on expert judgement relating to the relative severity of a given distress. In pavement, for instance, alligator cracking is seen to be more costly to repair than transverse cracking and is therefore given a larger deduct value resulting in a lower condition index. Although this may be reasonable for pavements, any mathematics behind the quantitative relationships between deduct values is not well documented in the literature. Quantifiable damage indices for pavements such as those used in the Highway Development and Management (HDM) framework have been in widespread use outside of North America and with the introduction of Mechanistic-Empirical Pavement Design Guide (MEPDG), are now gradually being adopted in North America providing a more consistently defined structure for quantifying pavement distress. This paper briefly discusses the evolution of the classes of pavement indices from the traditional composite class indices through to damage indices and into those developed or now being developed to manage some other infrastructure classes including Infrastructure Value Indices. The paper then puts forward a framework for incorporating risk and reliability with asset value indices in such a manner that both of these performance indicators could be compared across asset classes. Finally the paper describes a recently developed, damage based, LOS Index that can readily be applied to virtually any infrastructure asset class and that conveys not only the condition of the asset but allows Asset Managers to gauge the severity and density of distress through a single index number. The index can be readily implemented at any level of agency experience and requires no sophisticated data collection technology. The paper demonstrates the application of the technique through a municipal transportation infrastructure example.
Manitoba Infrastructure (MI) desired a new, tall concrete median barrier capable of satisfying the Test Level 5 (TL-5) safety requirements of the Manual for Assessing Safety Hardware (MASH). It needed to fit within the footprint of an existing F-shape median barrier located in a narrow median. It also was required to address headlight glare from opposing traffic. The barrier was designed with a height of 1,250 mm, a maximum width of 600 mm and to resist a load of 845 kN applied at the top of the barrier. The Manitoba Constrained-Width, Tall Wall was optimised to withstand the design load while minimising the amount of steel reinforcement. Variations of the barrier were developed, including a bridge rail and a roadside barrier. The bridge rail was considered to be the critical design due to its narrow width and anchorage to a relatively thin, cantilevered bridge deck. Thus, one full-scale vehicle crash test was conducted on the bridge rail system to verify the entire family of barriers. A vertical back barrier (45.72 m long) was constructed. It had a height of 1,250 mm and widths of 450 mm at its base and 250 millimetres at the top. The upstream half of the barrier (22.86 m) was constructed on a simulated bridge deck that was 280 mm thick. A gap in the bridge rail was constructed that was 168 mm wide and a gap in the bridge deck that was 19 mm wide; these were placed mid-span to simulate an expansion joint. A steel cover plate was placed over the barrier joint to prevent vehicle snag. During the test, the tractor trailer impacted just upstream from the joint and was safely redirected. The barrier sustained minor damage in the form of cracks and spalling. Anchorage options were developed for use with the TL-5 barrier system, including a foundation slab and an independent footing. Transition systems were also detailed for the connection of the TL-5 median barrier to various other new and existing barrier shapes. Finally, Manitoba Infrastructure developed a full series of barrier systems for median and roadside conditions that will provide designers many options to create construction drawings for their projects that are specific for their site(s).