Browsing by Author "Rimjha, Mihir"

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    On Demand Mobility Cargo Demand Estimation
    Rimjha, Mihir (Virginia Tech, 2018-10-30)
    Recent developments in the shipping industry have opened some unprecedented trade opportunities on various levels. Be it individual consumption or business needs, the thought of receiving a package on the same day or within 4-hour from some other business or industry in the urban area is worth appreciating. The congestion on ground transportation modes is higher than ever. Since currently the same-day delivery in urban areas is carried mainly by ground modes, the catchment area of this delivery service is limited. The On-Demand Mobility for cargo can elevate the concept of express shipping in revolutionary ways. It will not only increase the catchment area thereby encompassing more business and consumers but will also expedite the delivery as these vehicles will fly over the ground traffic. The objective of this study was to estimate the total demand for ODM Cargo operations and study its effect on ODM passenger operations. The area of interest for this study was Northern California (17 counties). Annual cargo flows in the study area were rigorously analyzed through databases like Transearch, Freight Analysis Framework-4, and T-100 International for freight. The results of this study are presented through a parametric analysis of market share. The end product also includes the flight trajectories (with flight plan) of daily ODM cargo flights in the study region. The On-Demand Mobility cargo operations are expected to complement passenger On-Demand Mobility operations. Therefore, the effect of ODM cargo operations on the passenger ODM operations was also analyzed in this study. The major challenge faced in this study was the unavailability of datasets with the desired level of details and refinements. Since the movement of cargo is mostly done by private companies, the detailed records of shipments are often not public knowledge.
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    Urban Air Mobility: Airport Ground Access Demand Estimation
    Rimjha, Mihir; Hotle, Susan; Trani, Antonio; Hinze, Nick; Smith, Jeremy; Dollyhigh, Samuel (AIAA, 2021-08)
    This study aims to estimate passenger demand of Urban Air Mobility (UAM) for airport ground access trips while considering airspace restrictions in the Dallas-Fort Worth region. UAM is a concept mode of transportation designed to bypass ground congestion for time-sensitive, price-inelastic travelers using autonomous, electric aircraft with Vertical Takeoff and Landing (VTOL) capabilities. Airport ground access trips constitute a trip purpose that can utilize this mode. This study analyzes originating ground access trips for two major airports in the Dallas-Fort Worth region: Dallas-Fort Worth International Airport (DFW) and Dallas Love Field Airport (DAL). First, a mode choice model is calibrated on the existing airport ground access behavior. UAM demand is then estimated using the developed model, airspace restrictions, and the results from UAM demand stated-preference surveys in literature. Airspace restrictions consist of unusable pieces of airspaces based on current air traffic patterns, where the placement of UAM vertiports and overflying of UAM vehicles are prohibited. The demand model considers the trajectories of the UAM vehicles, which navigate on pre-defined routes inside Class-B airspace to prevent Air Traffic Control (ATC) involvement requirements. This study includes sensitivity analyses of UAM demand to the cost per passenger mile (CPM), number of vertiports placed in the region, and other secondary factors like vertiport location, intermodal cost, fixed cost, and average speed. Corridors with significant UAM demand are identified from the spatial distribution of demand and potential bottlenecks in the UAM network. The findings predict up to 4% market share of UAM for trips to the airport at the optimistically lower fare of $2 per passenger mile (in addition to the fixed cost of $23) and a 50-vertiport UAM network. Average Value of Times (VOTs) for business and non-business travelers are estimated to be around $57/hr and $36/hr, respectively. Business travelers comprise three-quarters of the total UAM demand because of relatively higher VOTs. Airport access trips in Dallas-Fort Worth region have considerable potential for UAM if the trip's price is below $4 per passenger mile (in addition to the fixed cost of $23).
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    Urban Air Mobility: Demand Estimation and Feasibility Analysis
    Rimjha, Mihir (Virginia Tech, 2022-02-09)
    This dissertation comprises multiple studies surrounding demand estimation, feasibility and capacity analysis, and environmental impact of the Urban Air Mobility (UAM) or Advanced Air Mobility (AAM). UAM is a concept aerial transportation mode designed for intracity transport of passengers and cargo utilizing autonomous (or piloted) electric vehicles capable of Vertical Take-Off and Landing (VTOL) from dense and congested areas. While the industry is preparing to introduce this revolutionary mode in urban areas, realizing the scope and understanding the factors affecting the attractiveness of this mode is essential. The success of UAM depends on its operational efficiency and the relative utility it offers to current travelers. The studies presented in this dissertation primarily focus on analyzing urban travelers' current behavior using revealed preference data and estimating the potential UAM demand for different trip purposes in multiple U.S. urban areas. Chapter II presents a methodology to estimate commuter demand for UAM operations in the Northern California region. A mode-choice model is calibrated from the commuter mode-choice behavior observed in the survey data. An integrated demand estimation framework is developed utilizing the calibrated mode-choice model to estimate UAM demand and place vertiports. The feasibility of commuter UAM operations in Northern California is further analyzed through a series of sensitivity analyses. This study was published in Transportation Research Part A: Policy and Practice journal. In an effort to analyze the feasibility of UAM operations in different use cases, demand estimation frameworks are developed to estimate UAM demand in the airport access trips segment. Chapter III and Chapter IV focus on developing the UAM Concept of Operations (ConOps) and demand estimation methodology for airport access trips to Dallas-Fort Worth International Airport (DFW)/Dallas Love Field Airport (DAL) and Los Angeles International Airport (LAX), respectively. Both studies utilize the latest available originating passenger survey data to understand arriving passengers' mode-choice behavior at the airport. Mode-choice conditional logit models are calibrated from the survey data, further used to estimate UAM demand. The former study is published in the AIAA Aviation 2021 Conference proceeding, and the latter is published in ICNS 2021 Conference proceedings. UAM vertiport capacity may be a barrier to the scalability of UAM operations. A heavy concentration of UAM demand is observed in specific areas such as Central Business Districts (CBD) during the spatial analysis of estimated UAM demand. However, vertiport size could be limited due to land availability and high infrastructure costs in CBDs. Therefore, operational efficiency is critical for capturing maximum UAM demand with limited vertiport size. The study included in Chapter V focuses on analyzing factors impacting vertiport capacity. A discrete-event simulation model is developed to simulate a full day of commuter operations at the San Francisco Financial District's busiest vertiport. Besides calculating the capacity of different fundamental vertiport designs, sensitivity analyses are carried to understand the impact of several assumptions such as service time at landing pads, service time at parking stall, charging rate, etc. The study explores the importance of pre-positioning UAM vehicles during the time of imbalance between arrival and departure requests. This study is published in ICNS 2021 Conference proceedings. Community annoyance from aviation noise has often been a reason for limiting commercial operations at several major airports globally. Busy airports are located in urban areas with high population densities where noise levels in nearby communities could govern capacity constraints. Commercial aviation noise is only a concern during landing and take-offs. Hence, the impact is limited to communities close to the airport. However, UAM vehicles would be operated at much lower altitudes and have more frequent taking-off and landing operations. Since the UAM operations would mostly be over dense urban spaces, the noise potential is significantly high. Chapter VI includes a study on preliminary estimation of noise levels from commuter UAM operations in Northern California and the Dallas-Fort Worth region. This study is published in the AIAA Aviation 2021 Conference proceedings. The final chapter in this dissertation explores the impact of airspace restrictions on UAM demand potential in New York City. Integration of UAM operations in the current National Airspace System (NAS) has been recognized as critical in developing the UAM ecosystem. Several pieces of urban airspace are currently controlled by Air Traffic Control (ATC), where commercial operation density is high. Even though the initial operations are expected to be controlled by the current ATC, the extent to which UAM operations would be allowed in the controlled spaces is still unclear. As the UAM system matures and the ecosystem evolves, integrating UAM traffic with other airspace management might relax certain airspace restrictions. Relaxation of airspace restrictions could increase the attractiveness of UAM due to a decrease in travel time/cost and relatively more optimal placement of vertiports. Quantifying the impact of different levels of airspace restrictions requires an integrated framework that can capture utility changes for UAM under different operational ConOps. This analysis uses a calibrated mode-choice model, restriction-sensitive vertiport placement methodology, and demand estimation process. This study has been submitted for ICNS 2022 Conference.
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    Urban Air Mobility: Preliminary Noise Analysis of Commuter Operations
    Rimjha, Mihir; Trani, Antonio; Hotle, Susan (AIAA, 2021-08)
    This study aims to estimate potential noise levels generated due to Urban Air Mobility (UAM) commuter operations in the Northern California and the Dallas-Fort Worth regions. UAM is a concept aerial transportation mode designed to bypass ground congestion using an electric vehicle with Vertical Take-Off and Landing (VTOL) capabilities. UAM vehicles are expected to be significantly quieter than traditional helicopters, but operate on a much larger scale. Commuter travel demand will not be uniformly distributed with operations concentrated in a small geographical area such as Central Business Districts (CBD) and short time windows such as morning or evening peak periods. The objective of this study is to evaluate the aircraft noise annoyance generated by commuter UAM operations using flight trajectories developed in a previous study estimating UAM commuter demand. This study estimates the noise level from overflying UAM vehicles in a full day of operation (24 hours) and identifies areas where the noise levels may pose a challenge to future UAM operations. Noise estimation is performed at the Census Block group level using the Day-Night Level (DNL) metric. We run a parametric analysis considering two scenarios in each region: the UAM vehicle has a 10 dBA and 15 dBA noise reduction compared to the Robinson R-44 helicopter. The findings indicate a considerable difference between the 10 dBA and 15 dBA reduction scenarios. Although challenging, achieving a 15-dBA reduction compared to a 10-dBA reduction could reduce land area with DNL value above 50 dBA by 94% and highly-annoyed population by 91% in Northern California. Similarly, in Dallas-Fort Worth, achieving a 15-dBA reduction compared to a 10-dBA reduction could reduce the land area with DNL value above 50 dBA by 80% and a highly annoyed population by 85%. Lastly, we analyze the high-demand vertiport in the San Francisco Financial District in the Aviation Environmental Design Tool (AEDT) to observe the DNL contours for the varying noise performance scenarios.