Data-Driven Design of On-Demand Multimodal Transit Systems

Across the United States, public transit agencies are facing trends of decreasing ridership. Especially during and since the COVID-19 pandemic, reduced ridership caused many agencies to have significant budget deficits due the to the high-fixed cost of traditional transit systems. Many transit planners are exploring network redesign to address these changing ridership patterns and their budget deficits. On-demand services have previous been used in smaller cities, and more rural areas and for paratransit services, but now larger cities are starting to explore using on-demand services to help supplement their fixed route services to create a more accessible and scalable system. On-demand Multimodal Transit Systems may be an accessible, scalable solution for first and last mile issues that often plague many transportation systems. Chapter 2 presents a novel methodology to help transit agencies with their tactical planning for post-game ridership of large events. The methodology has three main steps: (1) predicting the total post-game ridership; (2) combining the total prediction with historical trends to forecast the passenger flow curve at nearby stations after the game; and (3) estimating the required train frequencies to serve these customers with minimal passengers left behind by each train. Additionally, this chapter proposes a suite of data-driven techniques that together create a data-driven pipeline to exploit Automated Fare Collection (AFC) data for evaluating, anticipating, and managing the performance of transit systems. This chapter includes a case study where the proposed pipeline is used to generate an adjusted train schedule for the post-game period and simulated with the rail ridership data from the Metropolitan Atlanta Rapid Transit Authority (MARTA). The simulation results highlight how the proposed schedules based on the estimated required post-game train frequencies could significantly improve post-game congestion and wait time. Chapter 3 studies the resiliency during a pandemic of On-Demand Multimodal Transit Systems (ODMTS), a new generation of transit systems that combine a network of high-frequency trains and buses with on-demand shuttles to serve the first and last miles and act as feeders to the fixed network. A limit is imposed on the number of passenger transfers with a new network design model leveraging a transfer-expanded graph. It presents a case study for the city of Atlanta and evaluates ODMTS for multiple scenarios of depressed demand and social distancing representing various stages of the pandemic. The case study relies on a real data from MARTA, an optimization pipeline for the design of ODMTS, and a detailed simulation of these designs. The case study demonstrates how ODMTS provide a resilient solution in terms of cost, convenience, and accessibility for this wide range of scenarios. Chapter 4 addresses to what extent On-Demand Multimodal Transit Systems (ODMTS) in combination with Dedicated Bus Lanes (DBLs) improve the attractiveness of public transit under various congestion scenarios. Previous case studies have shown that ODMTS may simultaneously improve travel time, reduce system cost, and attract new passengers compared to existing fixed-route systems. However, none of these studies include the effect of congestion on the travel times, adoption, and cost of the ODMTS. This paper introduces new methods to help model the ODMTS under various congestion scenarios as part of a case study in the Metro Atlanta Area, analyzing the system both with and without DBLs. The results show that an ODMTS with DBLs and synchronization could make public transit a viable, accessible option for many more people, especially in currently underserved areas. Higher congestion actually leads an ODMTS with DBLs to be faster than a direct trip by car in some cases by mitigating the negative impact of congestion on the most congested corridor. Chapter 5 presents a novel mixed-integer program (MIP) formulation to incorporate bus line design into the network design problem for On-Demand Multimodal Transit Systems (ODMTS) that allows the model to accurately capture wait time and transfer costs in addition to travel time and vehicle costs. To solve large-scale instances, a two-stage reformulation is presented where the first-stage problem decides which bus arcs to open and decides which arcs immediately follow and the second-stage problem decides the multimodal path for each individual trip. The solution method is based on the Benders decomposition method and uses disaggregated subproblems and Pareto-optimal cuts. This chapter includes a case study of the Metro Atlanta Area with instances that have up to 43,000 unique trips and hundreds of bus arcs for potential lines. The results show there was a significant reduction in number of transfers for individuals when considering the bus lines as part of the network design phase.Ph.D

Measuring individual overpotentials in an operating solid-oxide electrochemical cell

We use photo-electrons as a non-contact probe to measure local electrical potentials in a solid-oxide electrochemical cell. We characterize the cell in operando at near-ambient pressure using spatially-resolved X-ray photoemission spectroscopy. The overpotentials at the interfaces between the Ni and Pt electrodes and the yttria-stabilized zirconia (YSZ) electrolyte are directly measured. The method is validated using electrochemical impedance spectroscopy. Using the overpotentials, which characterize the cell's inefficiencies, we compare without ambiguity the electro-catalytic efficiencies of Ni and Pt, finding that on Ni H_2O splitting proceeds more rapidly than H2 oxidation, while on Pt, H2 oxidation proceeds more rapidly than H2O splitting.Comment: corrected; Phys. Chem. Chem. Phys., 201

MARTA Reach: Piloting an On-Demand Multimodal Transit System in Atlanta

This paper reports on the results of the six-month pilot MARTA Reach, which aimed to demonstrate the potential value of On-Demand Multimodal Transit Systems (ODMTS) in the city of Atlanta, Georgia. ODMTS take a transit-centric view by integrating on-demand services and traditional fixed routes in order to address the first/last mile problem. ODMTS combine fixed routes and on-demand shuttle services by design (not as an after-thought) into a transit system that offers a door-to-door multimodal service with fully integrated operations and fare structure. The paper fills a knowledge gap, i.e., the understanding of the impact, benefits, and challenges of deploying ODMTS in a city as complex as Atlanta, Georgia. The pilot was deployed in four different zones with limited transit options, and used on-demand shuttles integrated with the overall transit system to address the first/last mile problem. The paper describes the design and operations of the pilot, and presents the results in terms of ridership, quality of service, trip purposes, alternative modes of transportation, multimodal nature of trips, challenges encountered, and cost estimates. The main findings of the pilot are that Reach offered a highly valued service that performed a large number of trips that would have otherwise been served by ride-hailing companies, taxis, or personal cars. Moreover, the wide majority of Reach trips were multimodal, with connections to rail being most prominent

Resiliency of On-Demand Multimodal Transit Systems During a Pandemic

During the COVID-19 pandemic, the collapse of the public transit ridership led to significant budget deficits due to dramatic decreases in fare revenues. Additionally, public transit agencies are facing challenges of reduced vehicle capacity due to social distancing requirements, additional costs of cleaning and protective equipment, and increased downtime for vehicle cleaning. Due to these constraints on resources and budgets, many transit agencies have adopted essential service plans with reduced service hours, number of routes, or frequencies. This paper studies the resiliency during a pandemic of On-Demand Multimodal Transit Systems (ODMTS), a new generation of transit systems that combine a network of high-frequency trains and buses with on-demand shuttles to serve the first and last miles and act as feeders to the fixed network. It presents a case study for the city of Atlanta and evaluates ODMTS for multiple scenarios of depressed demand and social distancing representing various stages of the pandemic. The case study relies on a real data from the Metropolitan Atlanta Rapid Transit Authority (MARTA), an optimization pipeline for the design of ODMTS, and a detailed simulation of these designs. The case study demonstrates how ODMTS provide a resilient solution in terms of cost, convenience, and accessibility for this wide range of scenarios

Steps Towards a Sustainable Hydrogen Production from Sunlight and Water

This chapter focuses on some aspects concerning the realization of an actually sustainable H2 production, and especially the need for earth abundant, environmental friendly, solar driven heterogeneous catalysis for the Water Oxidation reaction: the catalyst shall be thermodynamically and mechanically stable to allow cyclic long-term operations. The focus will be mainly on Mn- and Co-compounds, though reference will be made to other compounds, when appropriate

Energy storage in electrochemical capacitors: designing functional materials to improve performance

Electrochemical capacitors, also known as supercapacitors, are becoming increasingly important components in energy storage, although their widespread use has not been attained due to a high cost/ performance ratio. Fundamental research is contributing to lowered costs through the engineering of new materials. Currently the most viable materials used in electrochemical capacitors are biomass-derived and polymer-derived activated carbons, although other carbon materials are useful research tools. Metal oxides could result in a step change for electrochemical capacitor technology and is an exciting area of research. The selection of an appropriate electrolyte and electrode structure is fundamental in determining device performance. Although there are still many uncertainties in understanding the underlying mechanisms involved in electrochemical capacitors, genuine progress continues to be made. It is argued that a large, collaborative international research programme is necessary to fully develop the potential of electrochemical capacitors