Modeling

The Value Of Runway Time Slots For Airlines

Cao, Jia-ming
Kanafani, Adib
1997

In flight scheduling, airlines usually determine optimal timing for their flights to respond to time-dependent demand and the requirement of frequency plans, of available fleets and of aircraft routings. Nevertheless, it is unavoidable that some flights cannot actually operate at their expected time because of the capacity limit of the airport runway. Thus, adjustments have to be mad by altering some flights from their optimal times. Scarce runway time slots represent a resource whose value to the airline may be determined from the impact of such re-scheduling on the objective function of...

Achieving a Higher Capacity National Airspace System: An Analysis of the Virtual Airspace Modeling and Simulation Project

Smirti, Megan
Hansen, Mark
2009

The Virtual Airspace Modeling and Simulation (VAMS) project developed by the National Aeronautics and Space Administration (NASA) presents a detailed plan for increasing National Airspace System capacity. Interviews with aviation experts regarding the VAMS project led to lessons learned which can inform current modernization plans and processes, as the current system prepares for modernization. According to experts consulted, development should include a small number of project developers who provide periodic opportunities for wide stakeholder feedback; roadmaps should incorporate...

Asymptotic Approximations for the Transportation LP and Other Scalable Network Problems

Daganzo, Carlos F.
Smilowitz, Karen R.
2000

Network optimization problems with a "scalable" structure are examined in this report. Scalable networks are embedded in a normed space and must belong to a closed family under certain transformations of size (number of nodes) and scale (dimension of the norm.) The transportation problem of linear programming (TLP) with randomly distributed points and random demands, the earthwork minimization problem of highway design, and the distribution of currents in an electric grid are examples of scalable network problems. Asymptotic formulas for the optimum cost are developed for the case where...

The Ethical Challenges and Professional Responses of Travel Demand Forecasters

Brinkman, Anthony P.
2003

Thirty years ago scholars first presented convincing evidence that local officials use biased travel demand forecasts to justify decisions based on unstated considerations. Since then, a number of researchers have demonstrated convincingly that such forecasts are systematically optimistic-often wildly so-for reasons that cannot be explained solely by the inherent difficulty of predicting the future. Why do modelers-professional engineers and planners who use quantitative techniques to predict future demand for travel and estimate its potential impact on built and proposed transportation...

Compliance, Congestion, and Social Equity: Tackling Critical Evacuation Challenges through the Sharing Economy, Joint Choice Modeling, and Regret Minimization

Wong, Stephen D.
2020

Evacuations are a primary transportation strategy to protect populations from natural and humanmade disasters. Recent evacuations, particularly from hurricanes and wildfires, have exposed three critical evacuation challenges: 1) persistent evacuation non-compliance to mandatory evacuation orders; 2) poor transportation response, leading to heavy congestion, slow evacuation clearance times, and high evacuee risk; and 3) minimal attention in ensuring all populations, especially those most vulnerable, have transportation and shelter. With ongoing climate change and increasing land development...

An Analysis of Port Selection

Malchow, Matthew Brian
2001

The objective of this research is to study the competition among ports. In particular we study the relation between port characteristics and port market share of maritime traffic. Maritime carriers make two primary decisions that affect ports. In the long-term, they assign vessels to routes. In the short-term, they assign each shipment to a vessel and, with that vessel, a port. In this research, we assume that vessel schedules are fixed and model the assignment of shipments as a function of the attributes that describe each port. For a carrier, some assignments are simpler than other...

Dynamic Stochastic Optimization Models for Air Traffic Flow Management

Mukherjee, Avijit
2004

This dissertation presents dynamic stochastic optimization models for Air Traffic Flow Management (ATFM) that enables decisions to adapt to new information on evolving capacities of National Airspace System (NAS) resources. Uncertainty is represented by a set of capacity scenarios, each depicting a particular time-varying capacity profile of NAS resources. We use the concept of a scenario tree in which multiple scenarios are possible initially. Scenarios are eliminated as possibilities in a succession of branching points, until the specific scenario that will be realized on a particular...

Optimal Infrastructure System Maintenance and Repair Policies with Random Deterioration Model Parameters

Park, Sejung
2004

Accurate facility deterioration models are important inputs for the selection of Infrastructure Maintenance, Repair, and Reconstruction (MR & R) policies. Deterioration models are developed based on expert judgment or empirical observations. These resources, however, might not be sufficient to accurately represent the performance of infrastructure facilities. Incorrect deterioration models may lead to wrong predictions of infrastructure performance and selection of inappropriate MR & R policies. This results in higher lifecycle costs. Existing infrastructure MR & R...

Trust and Compassion in Willingness to Share Mobility and Sheltering Resources in Evacuations: A case Study of the 2017 and 2018 California Wildfires

Wong, Stephen D
Walker, Joan L
Shaheen, Susan A
2020

Advances in the sharing economy – such as transportation network companies (e.g., Lyft, Uber) and home sharing (e.g., Airbnb) – have coincided with the increasing need for evacuation resources. While peer-to-peer sharing under normal circumstances often suffers from trust barriers, disaster literature indicates that trust and compassion often increase following disasters, improving recovery efforts. We hypothesize that trust and compassion could trigger willingness to share transportation and sheltering resources during an evacuation.To test this hypothesis, we distributed a survey to...

Willingness of Hurricane Irma evacuees to share resources: a multi-modeling approach

Wong, Stephen D
Yu, Mengqiao
Kuncheria, Anu
Shaheen, Susan A
Walker, Joan L
2022

Recent technological improvements have greatly expanded the sharing economy (e.g., Airbnb, Lyft, and Uber), coinciding with growing need for transportation and sheltering resources in evacuations. To understand influencers on sharing willingness in evacuations, we employed a multi-modeling approach across four sharing scenarios using three model types: 1) four binary logit models that capture each scenario separately; 2) a multi-choice latent class choice model (LCCM) that jointly estimates multiple scenarios via latent classes; and 3) a portfolio choice model (PCM) that estimates...