Kendra K. Levine's blog

Friday Seminar: Quantifying the Impact of Flight Predictability on Strategic and Operational Airline Decisions

THA A340-500 taxiing for spot.

Tomorrow is the last day of the semester - well done, students! You made it to the end! It's also the last Friday Seminar for the school year. Wrapping things up in style, Berkeley Ph.D. candidate Lu Hao will present her research, "Quantifying the Impact of Flight Predictability on Strategic and Operational Airline Decisions."

The idea of predictability or (inversely) variability is not new in the field of ground transportation, where (un)predictability mainly refers to the unpredictable variations in travel time and is thus directly related to uncertainty of travel time. In the realm of commercial air transportation, there is limited knowledge of how to quantify predictability and assess the potential benefit of improved predictability. Moreover, different aspects in airline decision making require different considerations when trying to measure and assess flight predictability.

In this work, the concept and metric for flight predictability is developed for both strategic and operational airline decision making. For both aspects, the appropriate measure for predictability is defined and the behavioral relationship between predictability and decision making is revealed. The potential benefits from improved predictability are then assessed for the two aspects, using airport departure queue assignment optimization and benefit pool analysis. The saving from improved predictability is significant for both cases, if the right metric is used. Comparing the two aspects, the difference in measuring flight predictability is rooted in the different perspectives of airlines’ consideration.

The Seminar takes place in 212 O'Brien (note the different location!) from 4-5 PM on May 16, 2014. There will be no cookie hour. 

Friday Seminar: The Impact of Adverse Weather on Freeway Bottleneck Performance

Raindrops keep falling on my screen...

It's almost the end of the semester, but we still have two more Friday Seminars! This week is the penultimate seminar featuring Ph.D. candidate Joshua Seeherman. He'll be presenting his research, "The Impact of Adverse Weather on Freeway Bottleneck Performance."

Daily commutes in and out of major cities by automobile will likely encounter multiple locations of delay known as bottlenecks where demand exceeds capacity. It has been long perceived that the performance of these bottlenecks decrease when they are affected by adverse weather such as rain, snow, or fog. This project utilizes existing methodology to measure the discharge rate for four freeway bottlenecks in Orange County, California during both clear and adverse conditions. After confirming that the results agree with past literature, a new model will be proposed attributing different periods of bottleneck congestion during either wet, windy, or foggy conditions to specific weather characteristics. Generic results that can be applied to multiple sites will be shown which will validate the new proposal and hopefully provide guidance for other locations where wet weather is a significant source of delay.

The seminar will take place today, Friday May 9, 2014 from 4:00-5:00 PM in 212 O'Brien. (Note the room change!) Cookie Hour is on this week as well, at 3:30 in the library. 

Friday Seminar: Incorporating Predictability into Cost Optimization for Ground Delay Programs

Waiting

The Spring semester may be winding up, but we still have Friday Seminars! This week features UC Berkeley Ph.D. candidate Yi Liu presenting, "Incorporating Predictability into Cost Optimization for Ground Delay Programs."

When there is foreseen congestion at an airport, Ground Delay Programs (GDPs) are often implemented to balance arrival demand with available arrival capacity by holding inbound flights at their departure airports. Through this, GDPs transfer expensive airborne delay in the terminal airspace of the arrival airport to cheaper and safer ground delay at the departure airports. In the implementation of GDPs, emphasis has mainly been put on maximizing throughput while predictability is overlooked. As a result, planned and unplanned delays are assigned the same cost coefficient in the GDP cost optimization problem. This ignores the fact that unplanned delays require extra effort from both the flight operator side and the traffic manager side and cause more pain for the passengers, which should correspond to higher costs.

This work introduces the goal of predictability into GDP cost optimization under capacity uncertainty. This is accomplished by assigning extra premiums to unplanned delays and planned but un-incurred delay, due to their unpredictability. To estimate delay components in the cost functions, two stochastic GDP models are developed using continuous approximation and deterministic queueing theory: a static no-revision model and a dynamic model considering one GDP revision. The results from the case study show that unpredictability can have a strong impact on GDP decisions. Depending on the value of predictability, the proposed method may reduce system-wide cost by 10%.

The seminar takes place this Friday, May 2, 2014 in 534 Davis from 4-5 PM. Cookie Hour will commence at 3:30 in the library. See you there!

Friday Seminar: Improving Bus Service with a Scalable Dynamic Holding Control

Commuter Warning

This week's Friday Seminar features UC Berkeley Ph.D. candidate Juan Argote presenting his research on control methods for transit services in, "Improving Bus Service with a Scalable Dynamic Holding Control":

Service unreliability is widely recognized as one of the main deterrents for travelers to use buses as their mode of transportation. Bus systems are exposed to an adverse feedback loop that generates a tendency for them to fall out of sync. This tendency can be counteracted by the application of control strategies that regulate the motion of the buses. This is well known among transit operators and some research has been devoted to address the issue. However, existing methods that are simple enough to be scalable can only handle headway-based operations of a single line.

This research proposes a scalable control method that applies dynamic holding based on real-time conditions and that allows buses to stay on schedule. A formulation that generalizes dynamic holding control strategies is developed for isolated bus lines. Stability conditions are derived and a quasi-optimal control that requires minimal data is also presented. The performance of this control is validated through simulation. The control is then extended to corridors where multiple bus lines overlap. A real-world case study in San Sebastián, where a system of coordinated on-board devices was deployed, is used to validate the control performance in this type of scenario. Finally, the resilience of the control is assessed considering multiple potential adversities.

The seminar takes place on Friday, April 25 in 534 Davis from 4-5 PM. Cookie Hour will be in the library at 3:30. 

 

Examining Electric Vehicle Parking

Electric Vehicle Parking

Electric vehicle (EV) public parking has been rolling out in Berkeley but got a boost recently with station installed at both Whole Foods. The city is slated to get more municipal charging stations soon, including a pilot to look at curbside charging stations

There are mixed opinions about EV public parking options, with concerns about location and demand. Researchers are looking at activity models to overcome public perception and be more effective in urban areas. A new article from Transportation Research Part A: Policy and Practice continues the discourse. "Electric vehicle parking in European and American context: Economic, energy and environmental analysis," by Marta V. Faria, Patrícia C. Baptista, and Tiago L. Farias, applies a methodology for the placement of EV parking to Lisbon, Madrid, Minneapolis and Manhattan. They conclude:

This research confirms that the success of deploying an EV charging stations infrastructure will be highly dependent on the price the user will have to pay, on the cost of the infrastructure deployed and on the adhesion of the EV users to this kind of infrastructure. These variables are not independent and, consequently, the coordination of public policies and private interest must be promoted in order to reach an optimal solution that does not result in prohibitive costs for the users.

The full article can be read here.  

 

Friday Seminar: Reliability-Based Optimization for Maintenance Management in Bridge Networks

Brooklyn Bridge at Night, NYC

This week's Friday Semiar is all about bridge networks. UC Berkeley Ph.D. candidate Xiaofei Hu presenter her research with the talk, "Reliability-Based Optimization for Maintenance Management."

Incorporating network configurations in bridge management problems is computationally difficult. Because of the interdependencies among bridges in a network, they have to be analyzed together. Simulation-based numerical optimization techniques adopted in past research are limited to networks of moderate sizes. In this research, a simple framework is developed to determine optimal maintenance plans for large networks with many bridges. The objective is to minimize disruption, specifically, the extra travel distance caused by potential bridge failures over a planning horizon and under a budget constraint. It is conjectured and then verified that the expected increase in vehicle-miles travelled due to failures can be approximated by the sum of expected increases due to individual failures. This allows the network-level problem to be decomposed into single-bridge problems and tackled efficiently. The computational effort increases linearly with the number of bridges.

The seminar takes place this Friday, April 18th, 2014 from 4-5 PM in 534 Davis. Cookie Hour will be in the library at 3:30.
in Bridge Networks

Special Friday Transportation Seminar: Welcome to the Age of Access: Exploring the Sharing Economy and Shared-Use Mobility

Car sharing

This Friday, April 11 is a Special Friday Transportation Seminar. Sponsored by our new University Transportation Center, UC CONNECT, Federal Region 9 And in conjunction with the Transportation Engineering Program Open House. "Welcome to the Age of Access: Exploring the Sharing Economy and Shared-Use Mobility" will be a panel discussion moderated by Professor Susan Shaheen, Co-Director TSRC. Panelists include: Neal Gorenflo, Co-Founder Shareable; Ed Reiskin, Director of Transportation, SFMTA; Shomik Raj Mehndiratta, Lead Transport Specialist, the World Bank, Rick Hutchinson, CEO, City CarShare; Michael Jones, Principal & Founder, Alta Bicycle Share.

A panel of leaders of the sharing economy and shared-use mobility will introduce the burgeoning economy, discuss various forms of shared-use mobility (such as carsharing, public bikesharing, and web-enabled apps) and explore policy issues associated with scaling and with the integration of shared-use mobility services into the transportation landscape (such as privacy, open data, insurance, safety, equity). The discussion will explore the opportunities to be had in developing a robust public-private partnership, the obstacles that must be faced during this process, and the role research can take in informing the creation of policy.

This event, in honor of the launch of our new University Transportation Center, UC CONNECT, will be held in conjunction with Transportation Engineering’s open house welcoming potential graduate students to the program and to the UC Berkeley campus. Faculty, students, new students, and alumni are welcome to join us for this event. A reception will follow.

The special seminar take place this Friday, April 11th, 2014; 3:30 - 5:00 pm in the Banatao Auditorium, Sutardja Dai Hall. (Note: different time and different location!) There is also a reception to follow. Cookie Hour will still happen, but at 3:00 pm in the library. 

New Article: Macroscopic Fundamental Diagram and Public Transport

Changing Course in Urban Transport

A brand new article in Transportation Research Part C: Emerging Technologies examines a macroscopic fundamental diagram (MFD) and how it is applied to bi-modal urban networks. "A three-dimensional macroscopic fundamental diagram for mixed bi-modal urban networks," by (ITS alum) Nikolas Geroliminis, Nan Zheng,and Konstantinos Ampountolas investigates existence of a three-dimensional vehicle-flow MFD for bi-modal network.

Recent research has studied the existence and the properties of a macroscopic fundamental diagram (MFD) for large urban networks. The MFD should not be universally expected as high scatter or hysteresis might appear for some type of networks, like heterogeneous networks or freeways. In this paper, we investigate if aggregated relationships can describe the performance of urban bi-modal networks with buses and cars sharing the same road infrastructure and identify how this performance is influenced by the interactions between modes and the effect of bus stops. Based on simulation data, we develop a three-dimensional vehicle MFD (3D-vMFD) relating the accumulation of cars and buses, and the total circulating vehicle flow in the network. This relation experiences low scatter and can be approximated by an exponential-family function. We also propose a parsimonious model to estimate a three-dimensional passenger MFD (3D-pMFD), which provides a different perspective of the flow characteristics in bi-modal networks, by considering that buses carry more passengers. We also show that a constant Bus–Car Unit (BCU) equivalent value cannot describe the influence of buses in the system as congestion develops. We then integrate a partitioning algorithm to cluster the network into a small number of regions with similar mode composition and level of congestion. Our results show that partitioning unveils important traffic properties of flow heterogeneity in the studied network. Interactions between buses and cars are different in the partitioned regions due to higher density of buses. Building on these results, various traffic management strategies in bi-modal multi-region urban networks can then be integrated, such as redistribution of urban space among different modes, perimeter signal control with preferential treatment of buses and bus priority.

The full paper can be found here.

Friday Seminar: Transit Oriented Development

Ho Chi Minh City at Dusk

After a brieg hiatus, the Friday Seminars are back! This week's Friday Seminar features Dr. Hien Nguyen, a visiting scholar at the Institute of Urban and Regional Development, speaking on Transit Oriented Development.

Transit Oriented Development (TOD) has been seen as a strategy to accommodate increasing urban populations with reduced impacts on transportation networks and the environment in many cities. It was understood that approaches to build successful TOD differ significantly from place to place, depending upon circumstances such as differences in land development regulations, zoning ordinances, market forces, development opportunities, available transit services, regional economy, etc. Therefore, to build TOD in Ho Chi Minh City where motorcycles are prevalent in traffic flow should apply different approaches. This ongoing research tries to analyze and assess some policies dealing with motorcycles to integrate this highly maneuverable mean of transportation with MRT as well as to find out effective measures to promote pedestrians to/from MRT stations under the existing characteristics of urban form in Ho Chi Minh City.

The seminar is on Friday April 4th, from 4-5 PM in 534 Davis. Cookie Hour will be at 3:30 in the library. 

Assessing Airport Carbon Emissions

Descending through the LA smog

Much of the research about carbon emissions and transportation is focused on highways. A new article from the Journal of Air Transport Management proposes a model to examine carbon emissions and airports. Maria Nadia Postorino and Luca Mantecchini authors of "A transport carbon footprint methodology to assess airport carbon emissions," write:

Airports are important nodes in the air transport system, but also local sources of environmental impacts. Emissions of CO2 are among the most relevant ones because of their potential greenhouse effects. Many policies and guidelines have been identified at national and world level to reduce such kind of impacts. In this paper, a Transport Carbon Footprint methodology has been set to identify Unit Carbon Footprints (UCFs) linked to some identified emission macro-sources – i.e., land vehicles, on-ground aircraft, airport handling and terminal equipment – to compute the contribution of the single macro-source to the total amount of CO2. Particularly, UCFs due to transport activities have been defined according to some relevant transport variables. The computation of UCF values for a given airport allows computing both the contribution of each macro-source and also evaluating the effectiveness of transport-related actions aiming at reducing the carbon impact. The methodology has been applied to the airport of Bologna, in Northern Italy, and its UCF values for the identified macro-sources have been computed.

The full article can be found here

 

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