Browsing by Author "Waters, Nigel"
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- ItemOpen AccessAccess to primary percutaneous coronary intervention for ST-segment elevation myocardial infarction in Canada: a geographic analysis(Open Journal Systems, 2010-02-02) Patel, Alka B; Tu, Jack V; Waters, Nigel; Ko, Dennis T; Eisenberg, Mark J; Huynh, Thao; Rinfret, Stéphane; Knudtson, Merril; Ghali, William A
- ItemOpen AccessDetermining geographic areas and populations with timely access to cardiac catheterization facilities for acute myocardial infarction care in Alberta, Canada(BioMed Central, 2007-10-16) Patel, Alka B; Waters, Nigel; Ghali, William A
- ItemOpen AccessDynamic Shared Autonomous Vehicle Fleet Operations with Consideration of Fairness(2021-04-27) Habib, Nouran; Kattan, Lina; Alp, Osman; Waters, Nigel; Saidi, SaeidThe future of urban transportation has arrived, and it is moving in the direction of enabling urban mobility platforms to provide shared mobility services, accelerating the shift away from personal vehicle ownership. New companies, like Uber and DiDi, are heavily investing in developing and testing emerging mobility technologies, including shared autonomous vehicles (SAVs). The full implementation of emerging mobility technologies is expected to deliver a transformative wave of urban reform. Besides, emerging mobility technologies could offer promising sustainable solutions that would optimize the usage of limited mobility resources. For instance, shared mobility services are convenient, flexible, cost- and time-efficient, and environment-friendly. Further, fully-autonomous vehicle (AV) technology surpasses human drivers in terms of costs, driving behavior, hours of service, and compliance with the plans of fleet operators. Currently, researchers are extensively studying the operations of SAV fleets that provide on-demand curb-to-curb mobility services. Specifically, they develop traveler assignment and scheduling algorithms that aim to match each traveler with a proper vehicle and plan the schedule of the vehicle simultaneously, including picking-up and dropping-off other travelers, based on a specific fleet objective. This thesis aims to fill an existing gap in the literature regarding introducing “equitable” methods to dynamic ride-sharing (DRS) systems. Thus, to meet the rising concerns of social justice, equity, and fairness in transportation systems, this thesis introduces the proportional fairness concept to DRS systems while considering the passenger heterogeneity in terms of their valuation of in-vehicle travel time. The proportional fairness formulation seeks to balance efficiency and fairness in resource allocation problems. The proportional fairness approach is then compared to two other approaches in a simulation-based environment implemented in MATSim (i.e., an agent-based transport simulator). In a centralized-fleet setting, the first approach aims to maximize traveler utility/satisfaction, while the second approach aims to maximize the total travelers’ utility. Simulation scenarios are tested to quantify the trade-offs between fleet size and vehicle maximum allowable occupancy. The performance of the three approaches is evaluated based on various performance measures from a fleet management perspective [e.g., the ratio of zero-occupant (i.e., empty-vehicle) fleet kilometers traveled to total fleet kilometers traveled], a traveler perspective (e.g., the average traveler wait time), and equity in resource allocation perspective (i.e., the Gini coefficient).
- ItemOpen AccessGeospatial patterns of comorbidity prevalence among people with osteoarthritis in Alberta Canada(2020-10-15) Liu, Xiaoxiao; Shahid, Rizwan; Patel, Alka B; McDonald, Terrence; Bertazzon, Stefania; Waters, Nigel; Seidel, Judy E; Marshall, Deborah AAbstract Background Knowledge of geospatial pattern in comorbidities prevalence is critical to an understanding of the local health needs among people with osteoarthritis (OA). It provides valuable information for targeting optimal OA treatment and management at the local level. However, there is, at present, limited evidence about the geospatial pattern of comorbidity prevalence in Alberta, Canada. Methods Five administrative health datasets were linked to identify OA cases and comorbidities using validated case definitions. We explored the geospatial pattern in comorbidity prevalence at two standard geographic areas levels defined by the Alberta Health Services: descriptive analysis at rural-urban continuum level; spatial analysis (global Moran’s I, hot spot analysis, cluster and outlier analysis) at the local geographic area (LGA) level. We compared area-level indicators in comorbidities hotspots to those in the rest of Alberta (non-hotspots). Results Among 359,638 OA cases in 2013, approximately 60% of people resided in Metro and Urban areas, compared to 2% in Rural Remote areas. All comorbidity groups exhibited statistically significant spatial autocorrelation (hypertension: Moran’s I index 0.24, z score 4.61). Comorbidity hotspots, except depression, were located primarily in Rural and Rural Remote areas. Depression was more prevalent in Metro (Edmonton-Abbottsfield: 194 cases per 1000 population, 95%CI 192–195) and Urban LGAs (Lethbridge-North: 169, 95%CI 168–171) compared to Rural areas (Fox Creek: 65, 95%CI 63–68). Comorbidities hotspots included a higher percentage of First Nations or Inuit people. People with OA living in hotspots had lower socioeconomic status and less access to care compared to non-hotspots. Conclusions The findings highlight notable rural-urban disparities in comorbidities prevalence among people with OA in Alberta, Canada. Our study provides valuable evidence for policy and decision makers to design programs that ensure patients with OA receive optimal health management tailored to their local needs and a reduction in current OA health disparities.
- ItemOpen AccessImpacts of Weather on Urban Bus Performance in the City of Calgary, Alberta(2023-02-23) Mohammadi, Mohammad; He, Jennifer (Jianxun); Saidi, Saeid; Zhou, Qi; Waters, NigelThere is an extensive body of literature on the impacts of adverse weather on traffic performance and transit ridership; however, only a few research have investigated the impacts of adverse weather on urban bus performance. Traffic congestion and unfavourable road conditions caused by adverse weather directly affect the performance of buses. Also, adverse weather impacts buses indirectly by affecting the passengers. This study aims to evaluate the impacts of adverse weather (rainy and snowy weather) on urban bus performance in the City of Calgary. This research focuses on the impacts of rain and snow on seven bus routes in the City of Calgary. Calgary Transit provided the automatic vehicle location and automatic passenger counter data for 2019-2021. The weather data was supplied by the Calgary International Airport and included daily snowfall and 5-minute rainfall data from 16 rain gauges along the bus routes. Statistical tests and public transit performance measures have been employed in this study to assess the impacts of rainy and snowy weather on the buses. The Man-Whitney test was used to identify significant changes in the median of ridership, run time, dwell time and travel time. In addition, Levene’s test was employed to capture significant changes in the variance of run time, dwell time and travel time. Moreover, six measures from four categories of public transit performance measures (schedule adherence, headway, travel time, and wait time) were used to evaluate the impacts of rainy and snowy weather on bus performance. On-time Performance, coefficient of variation of headway, service regularity, coefficient of variation of travel time, 90th-50th percentile travel time, and excess wait time were all used to determine the effect of rain and snow on bus performance. This study found that there is a negative impact of rainy and snowy weather is definite on bus performance. However, the level of impact varies by route and data groups, which suggests considering other influential factors on the performance of buses along with weather for more detailed results.
- ItemOpen AccessLocating En-Route Charging Stations and Time Points for a Transit Route with Battery- Electric Buses(2023-12-20) Esmaeilnejad, Seyedshahab; Kattan, Lina; Wirasinghe, Chan; De Barros, Alexandre Gomes; Waters, NigelWhile the acknowledged environmental benefits of battery-electric buses (BEBs) are widely recognized, their distinct differences from diesel buses necessitate adjustments in both route planning (including charging station placement) and operations (comprising schedule management and holding control). Overall, life cycle emissions of BEBs tend to be lower than those of diesel buses. However, the actual environmental impact depends on various factors, including the energy source for electricity generation, battery manufacturing practices, and disposal/recycling methods. Transitioning to electric buses, particularly in regions with a clean energy grid, holds significant potential for reducing greenhouse gas emissions and air pollution. The strategic placement of charging stations, their number, duration of charging, and station types all factor into the comprehensive planning process. These stations can be strategically situated at depots, termini, or even along the route. This study addresses the long-term planning and optimization challenge of revising formulations for dispatch policy, determining optimal en-route charging station locations and corresponding charging durations, and determining the location of the holding point and their slack time. This optimization endeavor aims to enhance passengers' waiting time, operational efficiency, and capital costs, all while mitigating the inherent variability arising from weather- induced ridership fluctuations and battery performance uncertainties intrinsic to BEBs while improving the reliability of the transit service. Two linear deterministic optimization models and a two-stage stochastic programming (SP) optimization process are developed to pursue these goals. These approaches facilitate the strategic placement of BEB charging stations along the route and calculate their associated charging times in addition to the placement of the time points. The application of these models encompasses both one-way and two-way operations. The practicality and efficacy of these methodologies are tested on two high-demand bus routes within Calgary's transit network. Additionally, the study evaluates the potential implications of charging station malfunctions, mainly focusing on scenarios where the maximum charging time is exceeded and its subsequent impact on operational schedules and BEB operation costs. Furthermore, the study explores the solution yielded by the stochastic model, using the expected value of perfect information as an evaluative metric.
- ItemOpen AccessLong Term Planning and Modeling of Ring-Radial Urban Rail Transit Networks(2016) Saidi, Saeid; Wirasinghe, Chan; Kattan, Lina; Schonfeld, Paul; de Barros, Alex; Ruwanpura, Janaka; Waters, NigelExtensive work exists on regular rail network planning; however, few studies exist on the planning and design of ring-radial rail transit systems. With more ring transit lines being planned and built in Asia, Europe and the America’s, a detailed study on ring transit lines is timely. This thesis is based on idealizing transit network in perfect ring-radial transit lines. An analytical model using the continuum approximation approach is first introduced to find the optimal number of radial lines considering a city with a radio-centric street network. An approximate analytical model for ring-radial rail network planning is then introduced allowing analysis of the feasibility and optimal alignment of a ring transit line in a city. The city of Calgary‘s light rail transit network and Shanghai metro network are used to illustrate the applicability and transferability of the model. The model is then extended to allow simultaneous consideration of radial and ring lines and analyzing a transit network with partial ring and radial lines. This extension allows a more realistic idealization and analysis of rail transit networks. A benchmark analysis of cities with ring transit lines is used to identify prominent types of lines in idealized ring-radial transit networks. The cities are then assessed based on their unique network patterns using identical model inputs such as length of rail transit network and trip distribution patterns. This thesis provides a decision support tool for transit planners to compare the performance of different rail transit network extension alternatives for long-term rail transit planning. It can also be used for cost- benefit analysis to compare total generalized passenger cost savings versus the cost of network extension. Unlike simulations and agent-based models, this model is shown to be easily transferable to many ring-radial transit networks. Therefore, with a daily OD trip matrix and transit network supply characteristics and parameters as input, the model can be implemented for many radio-centric cities. The benchmark analysis using the combined universal ring-radial rail transit network model is a mathematically sound platform to compare different rail transit networks and propose the best examples of rail network topologies.
- ItemOpen AccessReal-Time Bus Information: Users’ Perspectives and Arrival Time Estimations(2017) Rahman, Md. Matiur; Wirasinghe, Sumedha Chandana; Kattan, Lina; Chien, Steven; De Barros, Alexandre; Wan, Richard; Waters, NigelThe uncertainty in bus arrival times creates a significant disutility; the provision of real-time bus arrival information is reported as a cost-effective way to reduce this disutility. From a wide viewpoint, this study attempts to contribute on two main topics. One goal is to reveal the transit users’ perspectives regarding real-time bus information by conducting a users’ survey. The other goal is to provide insights on the improvement in reliability of real-time bus arrival estimates. Regarding the users’ perspectives, this study investigated several aspects such as the preferred formats (point or interval estimate) of estimated arrival information, the value of real-time information under different weather condition, and disutility of headway in a scheduled and real-time information system. Results showed that a majority of the respondents preferred the interval estimate over the point estimate. The value of real-time information was $0.59 and $0.41 per trip when the weather was below and above 0°C, respectively. The disutility of bus headway of a real-time information system was found to be around half of the disutility of a scheduled information system. This study investigated the improvement in reliability of bus arrival time estimations in three parts. The first part examined the impact of the time interval of measuring real-time bus location (GPS) data on the accuracy of bus arrival estimations. Incorporating real-time bus location data below a 30-second time interval did not increase the accuracy of the applied estimation models. Estimations based on current and average historical bus speed outperformed other estimations only if the time interval of the location data was short (about two minutes). Estimations that relied on similar historical trips were more accurate when both the estimation horizon and time interval were longer. Horizon is defined here as the distance between the point for which the estimation is made and the location of the bus at the time of estimation. The second part investigated the changes in bus travel time characteristics with horizons. The experimental results showed that a significant change in bus travel time characteristics was observable around a horizon range of 7-8 km. The analysis of changes in probability densities with pseudo horizons showed that bus travel time distribution converges from a rightly skewed distribution to a more symmetrical distribution from a shorter to a longer pseudo horizon in general. Lognormal and normal distributions are found to be the best distributions for before and after a cut-off horizon of 7-8 km, respectively. The third part was about the development of Bayesian models to provide dynamic bus travel time distributions that was updated in light of new observations and include the estimation uncertainty chosen by users or transit service providers. Two models were developed in a Bayesian framework to achieve this objective: Model 1 uses the dynamic linear model (DLM) concept and Model 2 uses the dynamic regression model (DRM) concept. Support vector regression (SVR), which is reported in the literature to outperform several other existing methods is also applied as a benchmark to compare the performance of the developed estimation models. The proposed DLM, DRM, and SVR models were implemented for two different but regular bus routes with diversified service areas in Calgary. The experimental results showed that the proposed DLM and DRM outperformed the SVR model for both routes. It was found that the root mean square error (RMSE) decreased by 13-23% for DLM and DRM compared to the SVR model with the same inputs. The performance of the SVR model was similar to the DLM and DRM for a shorter horizon. However, DLM and DRM yielded much better estimations for a longer horizon. Considering accuracy, computational time, and ability to update the estimation based on the new bus travel time trend, the results of this study suggest that the DLM and DRM are promising real-time bus travel time estimation models, particularly for providing estimations that include the uncertainty of the estimates.
- ItemOpen AccessTransportation GIS: GIS-T(Wiley, 2005) Waters, Nigel