Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993. / Includes bibliographical references (leaves 539-540). / by Ajay Gupta. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009. / Includes bibliographical references (p. 163-174). / This research develops a systematic approach to analyze the computational performance of Dynamic Traffic Assignment (DTA) models and provides solution techniques to improve their scalability for on-line applications for large-scale networks. DTA models for real-time use provide short-term predictions of network status and generate route guidance for travelers. The computational performance of such systems is a critical concern. Existing methodologies, which have limited capabilities for online large-scale applications, use single-processor configurations that are less scalable, and rely primarily on trade-offs that sacrifice accuracy for improved computational efficiency. In the proposed scalable methodology, algorithmic analyses are first used to identify the system bottlenecks for large-scale problems. Our analyses show that the computation time of DTA systems for a given time interval depends largely on a small set of parameters. Important parameters include the number of origin-destination (OD) pairs, the number of sensors, the number of vehicles, the size of the network, and the number of time-steps used by the simulator. Then scalable approaches are developed to solve the bottlenecks. A constraint generalized least-squares solution enabling efficient use of the sparse-matrix property is applied to the dynamic OD estimation, replacing the Kalman-Filter solution or other full-matrix algorithms. Parallel simulation with an adaptive network decomposition framework is proposed to achieve better load-balancing and improved efficiency. A synchronization-feedback mechanism is designed to ensure the consistency of traffic dynamics across processors while keeping communication overheads minimal. The proposed methodology is implemented in DynaMIT, a state-of-the-art DTA system. Profiling studies are used to validate the algorithmic analysis of the system bottlenecks. / (cont.) The new system is evaluated on two real-world networks under various scenarios. Empirical results of the case studies show that the proposed OD estimation algorithm is insensitive to an increase in the number of OD pairs or sensors, and the computation time is reduced from minutes to a few seconds. The parallel simulation is found to maintain accurate output as compared to the sequential simulation, and with adaptive load-balancing, it considerably speeds up the network models even under non-recurrent incident scenarios. The results demonstrate the practical nature of the methodology and its scalability to large-scale real-world problems. / by Yang Wen. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997. / Includes bibliographical references (p. 80-81). / by David E. Brown. / M.S.

Massachusetts Institute of Technology. Dept. of Civil Engineering. Thesis. 1974. M.S. / MICROFICHE COPY ALSO AVAILABLE IN BARKER ENGINEERING LIBRARY. / Bibliography: leaves 110-111. / M.S.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005. / Includes bibliographical references (p. 267-271). / This thesis reviews the jet grouting methodology, and the current state of practice and research. Current methods of prediction of jet grout diameters are highly empirical and site specific, and do not take into account the jet hydrodynamics and soil properties explicitly. A rational model to describe the jet excavation mechanism for cohesive soil is presented in this thesis, with the aim of providing an improved prediction tool that can be used in jetting design. The model is based on the assumption that the velocity distribution in the cutting jet is equivalent to that of a free jet with boundaries corresponding to the dimensions of the cavity excavated in the ground. The shape of the cavity formed depends on the erosional properties of the soil and jet expansion is limited by the resistance at the jet-soil interface. It is hypothesized that the shape of the cavity excavated follows the locus of the jet radius satisfying the condition of constant wall shear stress. The model predicts that the limit of jet penetration is reached when the dynamic pressure at the jet tip becomes equal to the ultimate soil bearing resistance. The model was validated by laboratory jetting tests, using soil specimens manufactured from powdered kaolin clay, cement and water. Cement-soil ratios (CSR) of 2.5 to 7.5% were used to produce specimens with undrained shear strength (Su) ranging from 5 to 45 kPa. A period of at least 3 days was allowed for the specimen to cure in the test tank before jetting was commenced. The tests were conducted using different nozzle diameters, jetting pressures, rotation speeds and soil strengths. The specimens were exhumed after completion of each test to map the shape of the cuts excavated. / (cont.) The insitu shear strength of the specimens was obtained using torvane and laboratory vane shear tests. Samples were also obtained for density and moisture content measurements. The experimental results showed that the measured and predicted shapes of cut were in reasonable agreement, with the predicted jet width being conservative in most cases. A strong linear correlation was found between jet penetration, nozzle diameter, nozzle pressure difference and soil bearing capacity. It was found that a bearing capacity coefficient (Sc) of 2.4 was applicable for failure at the jet tip. This value of Sc was corroborated by field trial data. Wall shear stresses back-calculated from the experiments were much smaller than the residual soil strengths obtained from laboratory vane shear tests and correspond more closely to the erosional strength of clays. The model enables the lift step of the jetting monitor to be computed directly. The present research demonstrated that valuable information regarding the excavation mechanism can be obtained by careful examination of the actual cut in a soil formed by a jet. It is recommended that further work be done to investigate the erosional process at the jet-soil interface and the properties of the grouted soil, using higher jetting pressures and soils with higher shear strengths. The effect of withdrawal rate on column formation and uniformity of mix is of interest. The brittleness of the grouted product and its effect on strength and deformation behavior is also important. / Chu Eu Ho. / Sc.D.

Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 125-128). / Public transportation agencies, much like other service industries, have a constant churn of their customer base. New customers are entering and current customers are defecting every day. Traditionally, efforts to increase this customer base have focused on attracting more first-time users. However, preventing the loss of customers to competitive modes, such as the auto, has many added benefits that are not often realized. Loyal customers provide recommendations to others, increase and diversify their use of the service, and do not require the acquisition costs associated with new customers. This study aims to develop a strategy to identify the key drivers of customer loyalty to public transportation agencies, using the Chicago Transit Authority (CTA) as a case study. Once these influencing factors have been identified for the general population, loyalty differences between key market segments can be tested and analyzed. Based on these results, specific areas of service provision can be targeted for improvement and marketing campaigns can be developed so that customer segments can be targeted based on which areas are most important to them. Factor analysis and structural equation modeling were used to create a customer loyalty model for the CTA. Factors identified as contributing to a rider's loyalty were problem experience, perceptions of service quality', service value, perceptions of CTA, and customer satisfaction. / (cont.) The results for the general population showed that the average customer bases their decision to continue to use the service in the future fairly evenly on perceptions of service quality, service value, and customer satisfaction with the remaining two factors playing only indirect roles. The most important factor for a customer to recommend the service to others is their perceptions Qf service quality. The model results were then applied to key market segmentations (captive vs. choice riders, riders with low vs. high accessibility to transit, and bus riders vs. rail riders) using ANOVA, MIMIC, and multiple group analysis. It was found that captive riders are highly sensitive to problem experience; they report experiencing more problems and those problems more strongly influence the rest of the loyalty model. Riders with high accessibility generally rate all model factors higher than those with low accessibility and are, in turn, more loyal. Finally, bus riders' loyalty is more highly affected by their perceptions of service quality which could stem from the unpredictability of bus service resulting from exogenous factors. By developing a more thorough understanding of what keeps their customers coming back, public transportation agencies can more effectively use their limited resources by growing a base of loyal customers, and in turn, increasing their revenues. / by Valerie Webb. / S.M.in Transportation

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999. / Includes bibliographical references (leaves 58-60). / by John S. Wass. / M.Eng.

Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 131). / This thesis provides an overview of the US air cargo industry since airline deregulation in 1978, including a brief overview of the historical evolution of air cargo transport in the US from the early 1900s until the late 1970s and a discussion about the major international factors affecting global air cargo. A deeper analysis of the US air cargo industry follows these background discussions, emphasizing the growth of all-cargo carrier traffic in the past 30 years while noting the decline of combination carrier traffic within the past decade. Furthermore, operating cost analyses for the past 20 years reveal that major improvements in labor productivity have helped all-cargo carriers and combination carriers decrease unit costs, even while the price of fuel has risen dramatically. Productivity of US air cargo carriers is explored from 1990 to 2010 through two types of metrics, single-factor productivity (SFP) and multi-factor productivity (MFP). SFP metrics measure an airline's ability to turn inputs, such as fuel, labor, and capital, into outputs, such as available ton-miles (ATMs) and revenue ton-miles (RTMs). The MFP metric presented measures how effectively an airline produces an output from multiple inputs, essentially combining the SFP metrics. Single-factor productivity results show that the US air cargo industry has made significant improvements in labor productivity and capital productivity, with minor improvements in fuel productivity. FedEx and UPS have achieved the smallest improvements over the past 20 years, while other all-cargo carriers and combination carriers realized substantial advancements in the past two decades. Multi-factor productivity results echo the SFP results. Over the past 20 years, FedEx and UPS improved MFP 18%, combination carriers became approximately twice as productive, and the other all-cargo carriers increased MFP dramatically. However, questionable data reported by all-cargo carriers and methods used to determine only cargo-related data for combination carriers limit the accuracy of these results and caused difficulties calculating productivity throughout this thesis. / by David J. Donatelli. / S.M.in Transportation

Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 89-91). / This thesis describes the design and implementation of the key parts of an open payment system that supports mobile phone ticketing for the Long Island Railroad (LIRR), a part of the New York Metropolitan Transportation Authority (MTA). While many public transit agencies across the world are still using traditional fare systems, open payment system can help reduce lifecycle costs for transit agencies while making public transit service more convenient to passengers. One of the keys to the implementation of an open payment fare system is to infer trips and compute fares from a series of taps on gates and fareboxes by an open payment device, either a bankcard or a mobile phone. A trip construction algorithm based on a finite state machine is proposed to automatically group tap events from a single user into trip segments according to the MTA's fare rules and send them to a fare engine for fare calculation. The trip construction algorithm (implemented in the trip server) can handle bus, subway and railroad tap events in the MTA's system with fraud detection and exception handling. The fare engine adapts a label-correcting shortest path algorithm to find the chosen paths for each trip segment and to calculate the fare based on the LIRR's fare structure, including a number of configuration parameters such as minimum fare, minimum transfers and minimum travel time. The shortest path algorithm runs on a directed graph that is capable of modeling LIRR's complex service and transfer restrictions. Recognizing the limitations of system-specific fare engine design, this thesis also proposes extensions to the General Transit Feed Specification (GTFS), and develops a generic fare engine design that can be shared across multiple transit systems. These extended designs are studied and tested on the LIRR and Transport for London (TfL) networks. The proposed design appears to accommodate the fare policies of many transit systems; eight systems are briefly reviewed. / by Yin Wang. / S.M. in Transportation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / Buses and in general at-grade public transportation remain the most important component of transit services in all the urban areas, whether they are feeder to a heavy rail system or an independent network. However, the steady increase in travel demand, essentially private automobile, has results in a growing level of congestion, affecting both cars and public transportation. In response, cities like Curitiba and Zurich moved in the late 70's towards the implementation of preferential treatment. To do that, they introduced innovative policies in order to give the full priority to transit. Preferential treatment is a broad definition that combines all the means to insure that priority is given to transit (queue jump, traffic signal priority, exclusive lane, tramways ...). The main concerns about Zurich and Curitiba are that they both achieved their implementation through particular policymaking processes; moreover the generalization of these types of policies has been very limited. The objectives of this thesis are to apply the three models from the agenda-building theory (Mobilization, Inside Access and Outside Initiative) to the context of public transportation to understand how innovative policy-making can be introduced and if the presence of a policy entrepreneur is necessary and sufficient. Using 11 cities in Europe and America that have implemented preferential treatment as case studies, the thesis identified elements necessary to address the public reaction, the institutional fragmentation and the decision-makers' positions. The research shows the necessity of public consultations and comprehensive planning exercises to convince the different stakeholders. Moreover, it points out the benefits of initiatives such as benchmarking or national legislation. Eventually, the thesis concludes that the policy-making theory can be expanded in acknowledging a combination of models to describe the preferential treatment's implementation process. On the other hand, the context of public transportation has evolved enough (concentration of decision powers and increasing public support) so that transit agencies can move towards implementation in focusing on stakeholder management strategies instead of relying on a policy entrepreneur. / by Michael Pulichino. / S.M.