108 research outputs found
Supplemental Material - A clustering-based approach to quantifying socio-demographic impacts on urban mobility patterns
No full textSupplemental Material for A clustering-based approach to quantifying socio-demographic impacts on urban mobility patterns by Yang Yang, Samitha Samaranayake and Timur Dogan in Environment and Planning B: Urban Analytics and City Science</p
Supplemental Material - Assessing impacts of the built environment on mobility: A joint choice model of travel mode and duration
No full textSupplemental Material for Assessing impacts of the built environment on mobility: A joint choice model of travel mode and duration by Yang Yang, Samitha Samaranayake and Timur Dogan in Environment and Planning B: Urban Analytics and City Science</p
Speedup Techniques for the Stochastic on-time Arrival Problem
Get PDFWe consider the stochastic on-time arrival (SOTA) routing problem of finding a routing policy that maximizes the probability of reaching a given destination within a pre-specified time budget in a road network with probabilistic link travel-times. The goal of this work is to provide a theoretical understanding of the SOTA problem and present efficient computational techniques to enable the development of practical applications for stochastic routing. We present multiple speedup techniques that include a label-setting algorithm based on the existence of a minimal link travel-time on each road link, advanced convolution methods centered on the Fast Fourier Transform and the idea of zero-delay convolution, and localization techniques for determining an optimal order of policy computation. We describe the algorithms for each speedup technique and analyze their impact on computation time. We also analyze the behavior of the algorithms as a function of the network topology and present numerical results to demonstrate this. Finally, experimental results are provided for the San Francisco Bay Area arterial road network to show how the algorithms would work in an operational setting
A reconfigurable shared scan-in architecture
No full textThesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 97-100).by Samitha Samaranayake.M.Eng
SHAREABILITY NETWORK BASED DECOMPOSITION APPROACH FOR SOLVING THE LARGE-SCALE SCHOOL BUS ROUTING PROBLEM
Get PDFWe consider the classic School Bus Routing Problem (SBRP) combined with alternate modes, where students are either picked up by a fleet of school buses subject to some constraints or transported by alternate transportation modes to a common destination (school). The constraints that are typically imposed for school buses are a maximum fleet size, a maximum walking distance to a pickup point and a maximum commute time for each student. This is a special case of the Vehicle Routing Problem (VRP) with a common destination. We propose a decomposition approach for solving this problem based on the existing notion of a shareability network, which has been used recently in the context of dynamic ridepooling problems. Furthermore, we build a connection between the weighted set covering problem and SBRP after decomposition via a shareability network. To scale this method to large-scale problem instances, we propose i) a node compression method of the shareability network based decomposition approach, and ii) heuristic-based edge compression techniques that works well in practice. We show that the compressed problem leads to an Integer Linear Programming (ILP) of reduced dimensionality that can be solved very efficiently using off-the-shelf ILP solvers. Numerical experiments on small-scale, large-scale and benchmark networks are used to evaluate the performance of our approach and compare it to existing large-scale SBRP solving techniques
MOBILITY-DRIVEN URBAN DESIGN
No full text44 pagesUnderstanding the implications of urban design choices on the mobility of cities while incorporating this understanding into very early stages of an urban design process, provides a unique opportunity to address modern urban issues such as walkability, sustainability, and public health. Major hindering factors in mobility aware urban design process are the lack of tools that can assist with the interactive workstream and the lack of effective metrics that can facilitate the design decision making. The key interest of this research is to explore the interface between the urban design agenda and the urban mobility research framework. Through developing a mobility simulation tool and implementing it in a design case, the thesis aims to see how urban mobilities can inform the generation of new urban morphology, and how such mobility-driven design approach can benefit the built environment
OPTIMAL NETWORK AND MANAGEMENT OF ELECTRIC VEHICLE CHARGING STATIONS AT UNIVERSITY CAMPUSES
Get PDFSupplemental file(s) description: Code and outputMotivated by the necessity to reduce GHG emissions by commuting vehicles and improve users’ convenience, this thesis is dedicated to proposing an optimal network and management of Electric Vehicle (EV) charging stations on campus making the most of the zero tailpipe emissions of EVs. The problem has been decomposed with identified critical components to construct a basic Mixed Integer Programming (MIP) model maximizing the convenience benefits and minimizing the construction costs. Moreover, an expanded model has been proposed in accordance with another sub-objective of gaining greater environmental benefits. Two models are solved by CPLEX in Python with necessary inputs from several sources. Last but not least, the validity of the models has been verified by linearized relaxation, sensitivity analysis, and scenario analysis, which prove the enormous applicability and capability of two models
Quantifying Inconvenience in Incomplete Urban Street Networks: A New Metric
Get PDFIncomplete networks are those in which a road/intersection are unavailable to route through. Information centrality has been used to quantify the efficiency loss due to incompleteness. We propose a new topological method to quantify this by summing the excess distances one must travel. The new metric (SED) is found to be significantly correlated with IC across three representative networks. It is distributed Weibull and we provide a theoretical basis as to why. IC is distributed as a power law with varying exponents. The research then proposes several metrics to rank networks based on different policy questions. From the IC one can rank by the network’s inherent inequity. From the SED, one can rank per median/modal SED, percentage of most susceptible nodes, and excess CO2 emitted. Finally, we propose how SED can be helpful in location setting and theorize the existence of a trade-off between SED and the network’s operating cost
TOWARD A SYSTEMATIC APPROACH TO THE FLEET SIZE ESTIMATION OF AUTONOMOUS MOBILITY-ON-DEMAND SYSTEMS
Get PDFThe objective of this study is to provide analytical guidelines for the design of shared-vehicle Autonomous Mobility-on-Demand (AMoD) systems. Specifically, we consider the fundamental issue of determining the appropriate fleet size from operational perspectives. In this study, we model and analyze the AMoD system, whereby all modes of personal transportation in a city are replaced by one centralized controlled fleet of automated vehicles. A framework which integrates traffic assignment, vehicles routing and automated vehicles rebalancing is provided to estimate fleet size. Experimental results, based on simulations, are provided using actual demand data obtained from NYC Taxi and Limousine Commission. Results reveal that in midtown Manhattan during weekday morning peak hours, an AMoD fleet whose size is 63% of that currently in operation can satisfy all travel demands with the passenger waiting time less than 6 minutes
Considering Financial and Environmental Factors in Airport Efficiency Measurement: A Network DEA Analysis for U.S. Airports
Get PDFThis paper applies network DEA to modeling US airport efficiency taking into account monetary expenditure and environmental impact of the undesirable taxiway delay, in order to provide airlines insights on investment potentiality and fuel cost from the delay of airports. We also enhanced the model inputs by using runway configuration in addition to merely counting area and number of runways in conventional DEA application. Outputs are also improved by further transform fuel consumption to pollutants emission from the social-good perspective. Results are illustrated for 44 airports in the United States over 2011-2015
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