The use of large quantities of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixtures is desirable due to environmental and economic benefits. However, recycled asphalt mixtures with high recycled materials contents are usually less workable; difficult to compact in the field; and more prone to cracking, raveling, and other durability-related pavement distresses. Recycling agents can rejuvenate the aged binders in the recycled materials to different degrees depending on type and dosage, facilitating the inclusion of increased amounts of recycled materials. Recycling agents modify the ultimate performance of the corresponding rejuvenated asphalt mixtures, thus estimating an optimum recycling agent dosage is critical to maximize its benefit without compromising the short- and long-term performance of the rejuvenated asphalt mixture. This study provides tools for estimating recycling agent dosage based on a target climate with minimum laboratory efforts by considering the type, source, and amount of recycled materials, and the source and grade of the base (virgin) binder. A total of 15 different recycled binder blends (base and recycled binders) and 32 different rejuvenated binder blends (recycled binder blends with recycling agent) were considered, including materials from eight states across the United States. Blending charts for recycled binder blends were established and verified, and later used to develop relationships to estimate the optimum dosage of recycling agent. The recycling agent optimum dosages were determined to match the continuous high-temperature performance grade (PGH) of the recycled binder blend to that required by the target climate, as this dosage yielded the best performance for rejuvenated binders and mixtures. Long-term rejuvenating effectiveness of recycling agents was verified by extensive evaluation of rejuvenated binder blends and mixtures. Discussion on optimizing RAP/RAS and base binder proportions and controlling the maximum dosage of recycling agent for economic and pavement performance considerations was also provided. Finally, practice-ready guidelines for evaluation, materials selection/optimization, and design of rejuvenated asphalt mixtures with high recycled materials contents were prepared.
Aging causes asphalt pavement materials to stiffen and embrittle, which leads to a high cracking potential. A practical and accurate laboratory conditioning procedure that can simulate long-term aging of asphalt concrete for performance testing and prediction is required in order to integrate the effects of aging in pavement performance prediction models and other mechanistic design and analysis methods. Recent studies have suggested that loose mix oven aging at 95 deg C is the most promising long-term aging method to simulate field aging. This study has developed a means to determine laboratory aging durations for asphalt mixtures that best reflect the time, climate, and pavement depth for a given pavement location in the United States. A rigorous kinetics model together with laboratory experimental results demonstrate that the laboratory aging duration that is needed to match a given field condition is independent of material-specific kinetics. Project-specific laboratory aging durations that match field aging at various pavement depths were determined for a broad set of materials. The project-specific aging durations were used to calibrate a kinetics-derived climatic aging index (CAI) that was then used to determine the laboratory aging duration to match field aging at any location of interest. The CAI-determined aging durations at 95 deg C were used to generate aging duration maps for the United States for three field ages (four years, eight years, and 16 years) to match field aging at three depths (6 mm, 20 mm, and 50 mm).
Diffusion between virgin and aged asphalt plays a critical role in ensuring a final uniform asphalt binder in mixtures containing recycled asphalt pavement (RAP). Understanding the diffusion phenomenon and determining the diffusion coefficient have a significant effect on asphalt mix design and asphalt mixture performance. In this study, a new method was proposed to utilize fluorescence microscopy to determine the diffusion coefficient of aged RAP binder in recycled mixtures. First, Fick’s second law was applied to quantify the diffusion process in a two-layered virgin-aged binder model and to obtain the analytical solution to the distribution of virgin and aged binders. Then, fluorescence microscopy was used in the laboratory to differentiate between virgin and aged binders and to back-calculate their concentrations from fluorescence image. The diffusion coefficient was determined by fitting the analytical solution to the laboratory concentration measurements. Comparison of the diffusion coefficient by the proposed method and that using the dynamic shear rheometer (DSR) method from the literature shows that the diffusion coefficient determined by fluorescence microscopy was of the same magnitude to, but slightly lower than, that by DSR method. The diffusion coefficient was also predicted using another theoretical method – free volume theory. Parameters describing the asphaltic model in the free volume theory were determined from analysis of the chemical structure of asphalt, viscoelastic relaxation properties, and glass transition temperature of asphalt as well as from the diffusion coefficient measured from laboratory experiments. Diffusion coefficient predicted by the free volume theory shows that diffusion coefficients of asphalt were closely dependent on temperature and asphalt type. A diffusion simulation was performed on plant mixtures using the diffusion coefficient obtained from fluorescence microscopy. The results showed that an almost complete diffusion was achieved within five minutes in a hot-mix asphalt mixture resulting in uniform asphalt film.
The price of asphalt binder continues to rise, state agencies are looking for sustainable ways to reduce the cost of asphalt pavements without compromising performance. One such alternative is the use of crumb rubber, derived from waste tires, in binders of asphalt mixtures. Blending virgin asphalt binder with ambient or cryogenic ground crumb rubbers along with additional modifiers to produce sustainable asphalt mixtures was studied. The modifiers evaluated include E-rubber (free flowing rubber pellets), SBS, sulfur, and R-polymer (reactive polymer polyolefin blend coated micronized rubber particles). Thermogravimetric analysis was used to determine the natural rubber to synthetic rubber ratio in te ground tire rubbers. Gel permeation chromatography was used to investigate the molecular structure and changes occurring in the asphalt binder on blending with rubber/modifier. Scanning electron microscopy was used to examine the physical nature of the binder blends. All of the binder blends were evaluated using the multiple stress creep recovery test. Mixtures prepared from modified binders were characterized using semi-circular bend (SCB) test at intermediate temperature and Hamburg wheel-tracking (LWT) test. Correlation of physical properties of crumb rubber modified asphalt binder with apparent molecular weight f binder components was examined. Asphalt mixtures containing ambient or cryogenic ground crumb rubber additives did not exhibit improved mixture intermediate temperature cracking performance as compared to conventional mixture as measured by SCB test Jc value. Addition of elastomeric high molecular weight polymer additives improved MSCR test results of binder blends when compared to rubber blends with no additional polymer additives. Addition of E-rubber or R-polymer to the asphalt binder improved SCB intermediate temperature test results of the corresponding mixtures. It was noted that the presence of high molecular weight elastomeric species in asphalt binder blends is necessary to obtain acceptable intermediate temperature cracking performance. Presence of crumb rubber in asphalt binder contributed to the increase in percent high molecular weight species that provided an enhanced mixture rut resistance.
The objective of this study was to investigate the effects of various factors affecting bond strength between hot mix asphalt (HMA) overlay and underlying pavement layers in the field. The effect of interface bonding on short-term pavement performance was also evaluated. A list of candidate HMA field rehabilitation projects was identified across the United States, representing different traffic and environmental conditions. These projects included the rehabilitation of new, existing, and milled HMA pavements, and PCC pavements. Each field project involved at least one slow setting and one rapid setting non-tracking tack coat material, thereby creating one or more pairs of tack coats for comparison. The HMA overlay construction used different types of tack coat materials at various residual application rates. Specimens were cored from the evaluated test sections at different service times to determine the interface shear strength (ISS) according to AASHTO TP 114, “Standard Method of Test for Determining the Interlayer Shear Strength of Asphalt Pavement Layers.” Results of this study showed the ISS was largely dependent on the type of pavement surface (i.e., HMA vs. PCC) receiving tack coat, and pavement surface texture (i.e., milled vs. non-milled). In general, milled HMA surface yielded the highest ISS, followed by new HMA, existing HMA, and PCC surface types. Non-tracking rapid setting tack coats with stiff base asphalt cement exhibited the highest ISS compared to slow setting tack coats. With respect to the effect of service time, ISS increases with service time due to tack coat curing effect and densification of overlays. Laboratory measured ISS values correlated well with short-term cracking performance of field pavements. Results presented herein were part of NCHRP Project 9-40A on te “Field Implementation of the Louisiana Interface Shear Strength Test.”
The current asphalt binder performance grading system employs Dynamic Shear Rheometer (DSR) testing to determine high and intermediate temperature rheological properties. In recent years, the ability to measure DSR instrument compliance has allowed researchers to reliably measure low temperature binder properties as well. Low temperature characterization using DSR requires substantially smaller amount of binder as compared to the currently employed binder testing method, the Bending Beam Rheometer (BBR). For these reasons and the possibility of using one piece of equipment for full characterization of asphalt binders, previous research has investigated DSR as an alternative to replace BBR testing by determining equivalent creep stiffness (S) and slope (m-value) from shear complex modulus. Different methods have been proposed to determine BBR specification parameters from DSP data and their viability has been evaluated primarily for virgin binders. The objective of this paper is to further assess the applicability of different methods to determine S and m-values from DSR data for four neat binders as well as extracted and recovered binders from eighteen different mixture samples. The variables within the mixtures include lab versus plant production, aggregate size and gradation, binder PG and source, and recycled material type and content. The methods employ different interconversion methods, ranging from exact interconversions to regressive-based estimates. The shear relaxation modulus or creep stiffness and slope are correlated to S and m-value measured from BRR testing. The study also investigates the impact and differences due to use different interconversion methods. The results show that the Christensen approximate interconversion is adequately able to predict parameters from DSR results that are equivalent to S and m-value determined from BRR testing. The exact interconverted shear creep stiffness and shear relaxation modulus using generalized Maxwell model are compared to lab measured S and m-values, results show that a linear relationship exists between these parameters. Finally, a simple equation is developed to enable estimation of BBR S and m-value from a single point measurement of complex shear modulus and phase angle. This contribution is expected to have a practical use by providing a platform to estimate low temperature specification parameters from a single point DSR measurement.
The objectives of this research study were to determine the effects of asphalt binder formulation and source on the performance of binders with the same continuous Performance Grade (PG) using recently developed asphalt binder and mixture tests and provide recommendations, if needed, concerning the following: (1) the effect of asphalt binder formulation and source on performance, (2) the current PG specification and (3) the tests used in this study.
Various asphalt binders were formulated so they would have the same continuous high and low PGs which would meet the AASHTO M 320 specifications for a PG 58-28 binder. Other binders were formulated to meet the AASHTO M 320 specifications for a PG 64-28 binder. Thus, theer were two target PGs. Three sources of straight run asphalt binders were obtained, although one source was eliminated because for most of the modifiers obtained for this study, the target PGs could not be met. This showed that whether a continuous PG can be achieved through modification is dependent on binder source and modifier type. The modifiers used in the formulations consisted of two sources of re-refined engine oil bottoms (REOB), aromatic oil, polyphosphoric acid (PPA) and an air-blown asphalt, either alone or in combination. It is believed these modifiers are becoming more commonly utilized to supply the required PG asphalt binders for today’s paving industry.
Asphalt binder formulation and source had an effect on fatigue cracking, cohesion, adhesion, moisture susceptibility and non-load associated cracking even though the binders had closely matching continuous PGs based on high and low temperature properties. They had no effect on rutting performance except when measured by the MSCR, or thermal cracking performance except when measured by the EBBR. In conclusion, not all asphalt binders with the same continuous PG will perform identically in regard to all distresses.
Perpetual asphalt pavement designs have been based on controlling horizontal strains at the bottom of the asphalt layer and vertical strains on top of the subgrade to prevent bottom-up fatigue cracking and subgrade rutting, respectively. Traditionally, single strain thresholds had been used as limits where damage accumulation begins and propagates. The concept of strain distribution was introduced at the National Center for Asphalt Technology (NCAT), and it was to better represent the wide response spectrum in asphalt pavements caused by the different loading and environmental conditions. The concept was developed based on information and data collected from the NCAT Pavement Test Track, and from this a limiting strain distribution was created to assist with perpetual pavement design. Several studies analyzed the criteria using pavement responses calculated from PerRoad predicted strains in Test Track sections and existing perpetual pavements. A limitation of the AASHTOWare Pavement ME Design software is its inability to output the pavement responses necessary for perpetual pavement design. The objective of this study was to analyze pavement response data predicted from an integration of the AASHTOWare Pavement ME Design software outputs and a JULEA based program developed at NCAT to create a limiting strain distribution for perpetual pavement design using the AASHTOWare Pavement ME Design software. Strains were calculated for Test Track sections using these tools and based on the results a limiting strain distribution was then further evaluated using eight sections that won Perpetual Pavement Awards. Results showed that the horizontal strain distribution obtained from Test Track sections could differentiate the sections with cracking and the sections that did not crack. In the further evaluation, the horizontal strain distribution from the perpetual pavements did not exceed the limiting strain distribution developed from the Test Track sections, except for a section which surpassed it by a small margin at the 80th percentile and higher percentiles. Vertical strains were also determined for these pavements and the current 200 microstrains at 50th percentile design criteria was met by all the sections.
Cold in-place recycling (CIR), cold central plant recycling (CCPR), and full depth reclamation (FDR) are techniques that can be used to rehabilitate deteriorated pavements or used in new pavement construction projects. Use of these techniques has been found to be both fiscally and environmentally beneficial. However, there is a lack of literature that examines the mechanistic behavior of these mixtures, particularly when it comes to asphalt mixture-related test methods. This paper presents a comprehensive analysis of data from repeated load permanent deformation (RLPD) testing, a laboratory test that describes a mixture’s rutting behavior, conducted on bituminously stabilized CIR, CCPR, and FDR mixtures. The mixtures were collected as a part of NCHRP 9-51, Material Properties of Cold In-Place Recycling and Full-Depth Reclamation Asphalt Concrete for Pavement Design. The permanent deformation behavior of specimens from 23 projects sampled between 12 and 24months after construction is presented. The impact of stabilizing or recycling agent as well as the presence of chemical additives on the permanent deformation behavior was considered. Density, one of the most prevalent factors in field-based quality control and acceptance of cold recycled mixes was also examined with respect to its impact on permanent deformation behavior.
Since subsurface stripping extent is important for maintaining the road network, Minnesota Department of Transportation (MnDOT) uses forensic measures such as coring. The destructive nature and lack of coverage provided by this accepted method makes finding nondestructive methods for detecting stripping of in situ asphalt pavements an important need for MnDOT and many other agencies. Stripping between hot mix asphalt layers can cause premature failure of pavements. Knowledge of the lateral location, depth and extent of stripping can affect the timing and type of pavement preservation, maintenance, or rehabilitation. This paper reports on use of a DX1821 antenna to collect data at a frequency step of 20 MHz ranging from 50 MHz to 3050 MHz with a dwell time of 7.52 microseconds using a GeoScope Mk IV control unit on a full-scale asphalt pavement constructed at the National Center for Asphalt Technology (NCAT) test track with built-in stripping. Signals from the known stripped and non-stripped locations were used to evaluate statistical and energy based approaches. It is shown that a maximum energy ratio method, an approach that has been successfully applied to acoustic emission applications in the past, can improve signal clarity for stripping detection using ground penetrating radar (GPR). These results are confirmed using highway speed measurements at the Minnesota Road Research Facility with core validation.
In asphalt plants, moisture fluctuations in aggregate stockpiles present a problem for process control. To improve the production process, real-time methods of monitoring aggregate moisture in stockpiles, cold feed bins, and on conveyor belts have been used with varying levels of success.
This paper presents a field-evaluation of the accuracy of a real-time measurement system for measuring moisture content of virgin aggregate mixes moving on a conveyor belt for asphalt production. This system uses nuclear techniques, with no components in contact with the material flow or the belt, to determine the moisture content. Due to its use of low activity radioisotopic sources and a safe design, the system is categorized as a ‘generally licensed’ device by the US Nuclear Regulatory Agency imposing minimal regulatory burden on the US plant owners.
This measurement system was evaluated during the 2015 and 2016 production seasons at a continuous-type asphalt plant in Wisconsin, USA. Based on the study, the moisture measurement system showed a good sensitivity to moisture in in aggregate mixes with 0.9% wt. response to a 1.0% wt. change in moisture. It also showed a good measurement precision of 0.1% wt. at one standard deviation for a 20 second averaging. Over one thousand samples, with limestone as the main aggregate type, were collected from the belt and were used for comparing the moisture measurements from the new system to that by the oven drying method. For the two methods, the correlation of determination was 0.69 and the difference in moisture content was 0.10 +/- 0.35% wt. at one standard deviation. The new method did not show dependence on the nominal maximum aggregate size of the mixes.
Our initiative set out to create a three-dimensional (3D) virtual learning tool that allows instructors and students to view and interact with models in a virtual simulated platform.
The process involved:
1) Streamlining the 3D model creation procedure
2) Building a model viewer for parts familiarization and task training
3) Creating an efficient production workflow for getting content into the custom model viewer.
Almost all Saskatchewan highways have long stretches of rural roads through flat agricultural land with little roadside development and very few intersections. Traffic volumes are often relatively low on these rural highway sections and the travel speeds on these highways are normally high. However these rural highways often have short sections passing through small urban communities. These highway sections in small urban communities often have higher traffic volumes than the adjacent rural highway sections. These highway sections in small urban communities may have to accommodate through traffic as well as provide access to local businesses and residences. At some of these locations, due to economic and population growth, transportation needs have evolved beyond what these highway sections and communities were originally designed for. Highways at some of these locations may also function as local community main streets, which mean that these highway sections can be characterized by frequent intersections, property accesses, pedestrians and cyclists, school zones, and roadside parking. As a consequence unique safety concerns are identified. For example vehicles accustomed to the high travelling speed outside the towns tend to drive fast and pose risks to local traffic, pedestrians, and cyclists in towns. Accommodation of the local traffic and vulnerable road users while maintaining appropriate mobility is very important in these situations. The Saskatchewan Ministry of Highways and Infrastructure has conducted safety studies for highway sections near and within towns’ urban limits to proactively identify safety issues for improvement. The first phase study was for highways through small towns with population less than 1,000 and the second phase study was for highways through larger towns with population greater than 1,000. The studies used methodologies such as stakeholders (ministry regional traffic engineers, municipal officials, and RCMP officers) surveys and discussions to identify situations/locations with potential safety risks, site visits and assessment, GIS analysis tool in collision data analysis and assessment of roadway geometrics and signings etc. The studies have identified some common opportunities for safety improvements system wide and have also identified some safety concerns at some specific locations in towns. Countermeasures have been recommended such as establishing graduated speed transitions on highway approaches to towns, improving conspicuity of intersections, and enhancing highway sections in town centres as community streets among others for traffic safety improvements.
As towns and cities throughout North America begin to show signs of aging, the number of emerging mature neighbourhoods and communities within municipalities has burgeoned. The rapid growth of these areas has created transportation safety problems of a magnitude and nature that are hitherto unknown to governing bodies.
Mature neighbourhoods are defined as those communities developed in the historic past that often consist of older and smaller dwellings built on properties with a sizable lot in quiet streets. As the supply of large properties in towns continues to decrease and the costs of developable land continues to increase, the demand and pressure to rebuild infills in mature neighbourhoods is expected to rise. Developers, or existing owners, are now looking into purchasing or converting existing properties and turning them into larger or multi-purpose residences that may be incompatible with the existing built-form, and which would create different safety issues on transportation.
Many municipalities such as the County of Strathcona and the City of Edmonton in Alberta are currently conducting studies to formulate Mature Neighbourhood Overlay (MNO) policies with a view to lessen the threat of loss of character in these redevelopment areas, to protect green spaces, and to balance needs with zoning regulations. While these initiatives to address the land use impacts are necessary and commendable, the same corresponding attention have not been paid to the impact on transportation that are often as challenging, given tight existing conditions and constraints. To be successful, care must be taken to ensure that these infill developments will not create a negative impact, a perceived or real hazard, or an unacceptable increase in traffic on local roads.
This paper sets out to explore some of the more critical issues on transportation in mature neighbourhoods. It examines the unique features within these communities such as the blending of future houses with existing buildings; demographics of residents; traffic calming measures and their implementation; curbside management; geometric conditions and constraints; driveway accesses, setbacks, and parking; roadway dieting; conditions created by senior living; high and low end condominiums, etc.; as they relate to transportation and traffic safety. Strategies, policies and guideline solutions are suggested. The importance of public engagement is highlighted. Case studies using Strathcona County as an example are cited. It is recommended that more encompassing studies in the future should be carried out by research bodies to formulate a best practice guideline document.
The Quebec Ministry of Transport, Sustainable Mobility and Transportation Electrification (Ministère des Transports, de la Mobilité durable et de l’Électrification des transports, hereinafter MTMDET) is responsible for the winter maintenance of an extensive road network. In Quebec, local roads (107,000 km) are under municipal jurisdiction, while the MTMDET is responsible for all provincial roads and highways (31,000 km).
The larger part (66%) of the provincial road network is maintained by private sector companies. The rest is maintained by the MTMDET (20%) and municipalities (14%).
Each year, the MTMDET uses over 800,000 tonnes of de-icing agent on its road network in the winter months, which has a considerable negative impact to varying degrees on nearby flora and fauna, water quality, soil quality and infrastructure. Water quality tests conducted in several lakes close to urban areas across the province of Quebec has shown that, in certain locations, chloride concentrations are steadily increasing. And in a few locations, these concentrations have surpassed the chronic toxicity threshold for aquatic life.
Considering that sodium chloride’s impact on the environment and on roadway infrastructures is well documented, the responsible use and management of this product is of primordial importance.
The 2nd Concession is a major north-south arterial corridor under the jurisdiction of The Regional Municipality of York (York Region). Located in the Town of East Gwillimbury, Ontario, the corridor crosses a popular conservation area and recreational trail, situated in the watershed of the East Holland River which is managed by the Lake Simcoe Region Conservation Authority (LSRCA).
York Region and the Town of East Gwillimbury are undergoing tremendous growth in population and employment. The 2nd Concession Project improves mobility and enhances the environment with sustainable, context sensitive infrastructure in response to growth.
The innovative, enhanced public outreach program included early and consistent stakeholder engagement with mandatory and non-mandatory public open house meetings, kitchen table discussions with residents, site visits, a “visioning” workshop and regular newsletters. This established a high degree of trust and resulted in early stakeholder buy-in which accelerated project timelines and saved tax dollars. The early identification of environmental enhancements resulted in a design that improves mobility for all corridor users including pedestrians and cyclists and promotes active transportation.
Civil and Geotechnical Engineering design practice primarily considers general slope stability, with surficial slope stability addressed with less design rigour. Long term surficial slope stability is commonly accomplished with vegetation in the form of grass lined slopes, where detailing of same is accomplished by the slope stability engineer, a vegetation specialist or an erosion control practitioner.
When removing in-situ organic material pre-construction, there is common misconception that topsoil replaced post-construction must be equal to, or greater than the depth of the original topsoil. Little, if any attention is given to examining the vegetation establishment capacity of the civil grade. Common practice is to place topsoil on top of civil grade with typically insufficient detailing considering mechanical sloughing or organic leaching. With increased slopes, more compacted subgrades and less compacted topsoil, there comes increased likelihood of surficial slope instability.
This paper examines surficial slope instability where design detailing may be a contributing factor to long term surficial slope instability; where instability is found within days, months, years or even decades.
Further, this paper expands on the potential contribution of the erosion control industry where commonly delivered ‘Best Management Practices’ may contribute to surficial slope instability.
Evidence will be brought to support discussion around less topsoil and greater diligence in design detailing, to cause long-term sustainable root establishment in the civil grade for more robust grass liner protection of engineered infrastructure.
Frost susceptible subgrade soils, when exposed to moisture and freezing condition, cause frost heaving on road surfaces. In cold climates, like Manitoba, many road sections experience surface roughness and pavement deterioration due to seasonal frost heaving and melting. Subgrade soils frost heave remedial measures such as removal and replacement, embankment construction using non-frost susceptible materials, soil stabilization or thick pavement structures are generally very costly and/or impractical. Moreover, available guidelines or study results for characterizing soils as frost susceptible and classifying into different severity levels vary widely. Remedial measures or management of frost heave issues also vary among highway agencies. All these variations or factors hinder the selection of an appropriate approach to deal with this issue.
In Manitoba, in the past, a subgrade soil was characterized as frost susceptible if it met several characteristics. If a soil was characterized as frost susceptible, the calculated structural number (SN) was increased by 25%. The historical basis for such characterization and a fixed adjustment is unknown. Manitoba has now adopted the “value for money analysis approach” for all design, construction and operational practices. This led to a review of the appropriateness of these method/practice and revise to meet Manitoba’s current needs. Manitoba has completed major changes to frost susceptibility characterization/classification and pavement structure design/analysis for frost susceptible subgrade soils. This led to a more cost-effective and reasonable pavement structure design and management. This paper presents the comparison of various frost susceptibility characterization and classification, Manitoba’s past practice and recent changes, and the impacts of these changes. This paper and presentation may be an educational opportunity for interested individuals or agencies.
Transportation Research Record 2540 contains the following papers: Development and Application of a Scale to Measure Station Design Quality for Personal Safety (Rahaman,M, Currie,G, and Muir,C);
Group and Single Pedestrian Behavior in Crowd Dynamics (Do,T, Haghani,M, and Sarvi,M);
Use of Agent-Based Crowd Simulation to Investigate the Performance of Large-Scale Intermodal Facilities: Case Study of Union Station in Toronto, Ontario, Canada (Hoy,G, Morrow,E, and Shalaby,A);
Streetcar Resurgence in the United States: Transit Strategy, Growth Machine Tactic, or Some of Both? (Ramos-Santiago,LE, Brown,JR, and Nixon,H);
Evaluating Pay-on-Entry Versus Proof-of-Payment Ticketing in Light Rail Transit (Currie,G and Reynolds,J);
Redesigning Rail Transit Short-Turn Operations: Case Study of Line 2 of the Shanghai Metro in China (Sun,Y, Schonfeld,PM, Lu,Y, and Zhou,M);
Planning Urban Ring Rail Transit Lines: Case Study of Shanghai, China (Saidi,S, Ji,Y, Cheng,C, Guan,J, Jiang,S, Kattan,L, Du,Y, and Wirasinghe,SC);
Integrated Line Planning and Train Scheduling for an Urban Rail Transit Line (Wang,Y, Pan,X, Su,S, Cao,F, Tang,T, Ning,B, and De Schutter,B);
Tapping into Delay: Assessing Rail Transit Passenger Delay with Data from a Tap-In, Tap-Out Fare System (Antos,J and Eichler,MD);
Study of Standing Passenger Density in Subway Cars Based on Passengers’ Spatial Comfort: Case Study of Beijing Subway Line 4 (Chen,F, Fang,J, and Wu,Q);
Time-Expanded Network Model of Train-Level Subway Ridership Flows Using Actual Train Movement Data (Stasko,T, Levine,B, and Reddy,A);
Impact of Platform Edge Doors on Passengers’ Boarding and Alighting Time and Platform Behavior (de Ana Rodriguez,G, Seriani,S, and Holloway,C);
Geographic Information System Concept of Operations as a First Step Toward Total Enterprise Asset Management: Metro-North Commuter Railroad Case Study (Kizner,T, Goldemberg,M, Shapiro,M, ten Siethoff,B, Wei,X, Fogel,D, Kennard,J, and Lu,A);
Tram Safety in Mixed Traffic: Best Practices from Switzerland (Marti,CM, Kupferschmid,J, Schwertner,M, Nash,A, and Weidmann,U);
Alternative Methods for the Calculation of Pedestrian Catchment Areas for Public Transit (Macias,K).
Transportation Research Record 2542 contains the following papers: Transportation Issues of Adults on the Autism Spectrum: Findings from Focus Group Discussions (Lubin,A and Feeley,C);
Travel Patterns, Needs, and Barriers of Adults with Autism Spectrum Disorder: Report from a Survey (Deka,D, Feeley,C, and Lubin,A);
Shaping the New Future of Paratransit: An Agenda for Research and Practice (Mulley,C and Nelson,JD);
Automated Sidewalk Assessment Method for Americans with Disabilities Act Compliance Using Three-Dimensional Mobile Lidar (Ai,C and Tsai,Y);
Prediction of Benefits of Special Taxi-Pooling Design for Large Transport Terminals: Case Study of Beijing West Railway Station (Yao,W, Wang,Y, Wang,N, Yang,G, and Zhang,C);
Spatiotemporal Pattern Analysis of Taxi Trips in New York City (Hochmair,HH);
Trying Out Mobility as a Service: Experiences from a Field Trial and Implications for Understanding Demand (Sochor,J, Karlsson,ICMA, and Strömberg,H);
Development of an Employer-Based Transportation Demand Management Strategy Evaluation Tool with an Advanced Discrete Choice Model in Its Core (Hasnine,MS, Weiss,A, and Habib,KN);
Designing an Automated Demand-Responsive Transport System: Fleet Size and Performance Analysis for a Campus–Train Station Service (Winter,K, Cats,O, de Almeida Correia,GH, and van Arem,B);
Understanding Carsharing Risk and Insurance Claims in the United States (Shaheen,S, Shen,D, and Martin,E);
Negotiation and Coordination in Carpooling: Agent-Based Simulation Model (Hussain,I, Knapen,L, Yasar,AUH, Bellemans,T, Janssens,D, and Wets,G);
Car2work: Shared Mobility Concept to Connect Commuters with Workplaces (Regue,R, Masoud,N, and Recker,W);
Autonomous Vehicle Fleet Sizes Required to Serve Different Levels of Demand (Boesch,PM, Ciari,F, and Axhausen,KW);
Dynamic Ridesharing: Exploration of Potential for Reduction in Vehicle Miles Traveled (Rodier,C, Alemi,F, and Smith,D).
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