Kendra K. Levine's blog

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

 

On Ramp for d3.js - March 20th!

 

Do you want to use d3.js to make data visualizations to effectively communicate your research but don't know where to start? This Thursay, March 20th, in the Lower Level of the Blum Center join VUDLab from 6-9 PM for On Ramp for d3.js.

Our "On Ramp for d3.js" is designed to get people across disciplines the needed tools and know-how to create simple and easy-to-manipulate data visualizations. By the end of the night, we plan to have our participants complete two web-based visualizations and get the baseline tools needed to begin learning d3.js on a more serious level. Think of our event as your first crash course in creating interactive tools to show off your work! We will be providing food and soft drinks for everyone (don't worry... we got you).

Details of the event can be found here

New from FHWA: Human Factors Assessment of Pedestrian Roadway Crossing Behavior

2012 09 19 - 171 - DC - Connecticut Ave Candids

Earlier this year FHWA issued a new research report as part of their ongoing research on pedestrian and bicycle safety. In Human Factors Assessment of Pedestrian Roadway Crossing Behavior, researchers collected data and used it to create a predictive model of pedestrian behavior. 

More than half of pedestrian fatalities occur at unmarked locations away from intersections. However, little research has been conducted to understand why pedestrians cross roadways at unmarked locations. As a result, this study sought to better understand the environmental influences on both where and when pedestrians elect to cross the road. This report examines more than 70,000 pedestrian crossings at 20 different locations. The circumstances of those crossings (pedestrians yielding to vehicles, vehicles yielding to pedestrians, and evasive actions) were documented and analyzed. A model using environmental factors as inputs is provided to predict where (marked crosswalk intersection or outside the marked crosswalk) pedestrians will cross the road.

The full report can be found here

Travel Demand Forecasting: Beyond the models and into reality?

Chicago road network

Recently the State Smart Transportation Inivitiative (SSTI) asked if travel demand forecasts from U.S. DOT were accurate

Their answer is no

In the post, "U.S. DOT highway travel demand estimates continue to overshoot reality", Eric Sundquist examines the projections in FHWA's 2013 Conditions & Performance report. He finds that the estimates for VMT growth were 5-6% higher than reality. Concluding:

Had the report based estimates on more current historic data—e.g., VMT trends for 2003-13, which grew at one-fifth the USDOT’s 1995-2010 estimate—the cost estimates would have dropped by tens of billions more, reducing pressure on budgets while freeing up funds to bring the existing system to a state of good repair.

The accuracy of travel demand models and forecast predictions is not a new issue and more people are questioning the methodoloy. This year's TRB Annual Meeting featured a workshop on the issue The Next 50 Years in Travel Analysis: What We Don’t Know but Need to Know. The moderator, David T. Hartgen, mentioned a recent paper he wrote, "Hubris or humility? Accuracy issues for the next 50 years of travel demand modeling," in Transportation. Hartgen, examining 50 years of forecasting, describes problems with accuracy and ways to imrpove models. Definitely a paper worth reading. 

Friday Seminar: Planning, Design and Technical Aspects of Rail Transit Lines and Networks

Railing on Water

This Friday's Seminar is not to be missed. University of Pennsylvania Professor Vukan Vuchic, who wrote the book on urban transit, will present, "Planning, Design and Technical Aspects of Rail Transit Lines and Networks."

Growth of cities and increasing car ownership in recent decades have created a great need to build rail transit systems – LRT, Metros and Regional Rail. With their high-performance and high level of service, these modes compete well with private cars and serve large ridership. Their permanence influences urban form and land use development with high livability. The characteristics and roles of these three major modes of rail transit will be described. The alignments of their lines and networks will be reviewed. Positive and negative characteristics of different types of lines, such as radial, diametrical, circle, trunk/branch and others will be defined. This will lead to a comparison of two basic types on networks, those with integrated and with independent lines, illustrated by examples from many world cities. Current trends and likely developments in the roles and usage of different high-performance rail transit modes, such as “in-fill stations,” articulated metro cars, double-decker Regional Rail cars, Unattended Train Operation– UTO, will be reviewed. References will be made to BART development, innovations and experiences, as well as other rail systems in the Bay Area, such as MUNI and Caltrain.

The seminar takes place Friday March 7, 2014 from 4-5 PM in 534 Davis. TRANSOC Cookie Hour will be at 3:30 in the library. 

Everybody's a Tourist? Rethinking the Driver Population Factor

objects in mirror

A new paper, "Rethinking the Driver Population Factor," from ITS Berkeley's own Joshua Seeherman and Professor Alexander Skabardonis takes a look at the driver population factor currently used in the Highway Capacity Manual

Freeway analysis procedures in the widely used Highway Capacity Manual (HCM) include the input of a driver population factor (Fp), which allows the analyst to adjust the demand depending on the familiarity of drivers with the roadway. This adjustment is based on the assumption that unfamiliar drivers will drive at slower speeds with longer headways and that higher capacity would therefore be required. However, little research supports the use of the Fp, and the HCM cautions against the use of Fp unless the analyst is fairly certain the traffic stream is actually unfamiliar with the roadway. As an experiment, three bottlenecks in California were selected and analyzed during the weekday peaks and weekend afternoons in periods during which the traffic stream was likely to be nonlocal. The results showed that the changes in flow were minor at all three locations. Further research with additional sites and an increased awareness of the definition of familiarity will be required to confirm the results from this research.

The full paper can be found online in Transportation Research Record no. 2395 or you can look at the hard copy in the library. 

Friday Seminar: Some Approaches to Enhance Road Safety: Beyond Engineering Based Strategies

Tomorrow's ITS Friday Seminar is Dr. Shashi Nambisan, a professor at the University of Tennessee, presenting, "Some Approaches to Enhance Road Safety: Beyond Engineering Based Strategies"

Road safety is a significant concern to a broad range of stakeholders. Various approaches and strategies have been used to enhance road safety across the world. In this regard, the 4 Es used to characterize safety initiatives are Engineering, Education, Enforcement, and Emergency medicine. The developed nations have adopted a more comprehensive approach to incorporate the 4 Es, while the less developed nations focus primarily on engineering initiatives. The seminar will highlight some of the strategies adopted in Las Vegas, Nevada and across Iowa in the United States. These will be complemented with comments about challenges involved in improving overall road safety in Kerala, India. Further, examples of effective non-engineering based strategies will be presented. The seminar will also touch upon lessons learned from these experiences, and key considerations that are important for sustainable success of campaigns to enhance road safety.

The seminar will take place Friday, February 28, 2014 in 534 Davis from 4-5 PM. TRANSOC Cookie Hour will be in the library at 3:30.

Friday Seminar: Travel Time Reliability and Network Traffic Performance

Travel Times

This week's TRANSOC Friday Seminar features Professor Hani Mahmassani of Northwestern University presenting "Travel Time Reliability and Network Traffic Performance: Selected Highlights from Recent Research"

Reliability of travel time in traffic networks is affected by a variety of factors,some external (e.g. demand surges, weather) and others inherent to the behavior of the traffic stream, reflecting complex dynamics among interacting agents. Yet remarkably simple collective effects emerge when examining the relation between the standard deviation of the trip time per unit distance to the corresponding mean at the network level. We examine this relation for several networks using both simulated and actual data from vehicle probes. We connect this variance to other traffic variables defined at the network level, providing a simple characterization of travel time reliability as a function of density. We consider within-day and day-to-day variability and propose a compound gamma model to capture overall variation. To evaluate the reliability implications of different transportation options and operational strategies using simulation tools, a scenario-based approach is proposed and demonstrated.

The seminar takes place this Friday, February 21, 2014 from 4-5 PM in 534 Davis. Cookie Hour commences at 3:30 in the library.

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