Friday, November 30, 2012

Funded PhD Positions Available in the Areas of E-Car and E-Bike Sharing Systems

Two funded PhD positions in the areas of "Electromobility and E-Car Sharing Systems" and "E-Bike and E-Bike Sharing Systems" are available at the Institute for Traffic, Transport and Regional Planning at the University of the Federal Armed Forces Munich, Germany. For more information visit:
http://www.unibw.de/bauv7/strassenverkehrstechnik-en/Stellenanzeigen-en

Thursday, November 29, 2012

Transit Ridership in Chicago since 1981


I plotted this graph using the ridership data provided by the The Regional Transportation Authority (RTA). The graph shows the total system ridership including Pace, Metra, CTA rail, and CTA bus in terms of annual unlinked passenger trips in millions over years since 1981. Transit ridership in Chicago was declining (on average) from 1981 to 1995. Since 1995, transit ridership is picking up again but it is far from its historical peak in 1981 with more than 800 millions unlinked trips. There is also a small peak in 2008 which is perhaps associated with the increase in gas prices. Also, note that the increasing trend in system ridership comes mostly from the roughly constant increase in CTA rail and Metra usage. Ridership for Pace and CTA bus services remains almost constant since 1995.

The question is whether the ridership continue to increase? What can planning and transit agencies do to maintain this increasing trend? What are the factors affecting transit ridership in Chicago?

"Why Are States Passing Up Billions in Federal Transit Funds?"

"Why Are States Passing Up Billions in Federal Transit Funds?" is a recent article on the Atlantic Cities.

Kelly Clifton, Associate Professor at Portland State University, asks:
"Is it urban vs. rural or problems coming up with match? Or just the desire for more roads?"
I personally think it's a combination of all. States with more rural areas (fewer large cities) are less interested to flex funds to transit. Perhaps, transit agencies are not also strong enough (or maybe interested enough) to lobby and make the "flexing" happen.

"The underlying point, emphasized by Tanya Snyder at Streetsblog in her coverage of the new report, is that states can decide to allocate more money to transit "without any changes to national transportation law."

Also, I believe that the transit ridership is the U.S. does not increase unless people's travel behavior changes. Such change does not happen by only investing in transit infrastructure in an isolated manner. Other influential factors such as land-use need to change too. As long as population and job densities stay low, land-use remains unmixed (residential + commercial + institutional), and so on, it is unlikely to see a big shift in favor of transit, walking, and biking.

CMAP Modeling Research Opportunities (RFP)

Chicago Metropolitan Agency for Planning (CMAP) has recently announced two RFPs:

  • RFP 097 (Agent-based Economic Extension to Mesoscale Freight Model): The purpose of this RFP is to extend CMAP’s current freight modeling application to include a means for preparing future freight scenarios sensitive to distinct conditions at the global scale and explicit policy interventions from within the CMAP region.
  • RFP 096 (Network Micro-simulation Extension to Activity-based Travel Model): The purpose of this RFP is to extend application of an activity-based model of travel demand to include dynamic sensitivity to multi-modal network conditions.

The deadline for receipt of submissions in response to the RFP is 3:00 p.m., January 7, 2013.

Wednesday, November 28, 2012

I-55 Managed Lane Project


IDOT is initiating the I-55 Managed Lane Project in the Chicago area. According to the project website:
"The scope of work for this project is anticipated to include the addition of one lane in each direction within the existing median of I-55 needed to accommodate implementation of a managed lane, which could include Express Toll Lane (ETL), High Occupancy Vehicles (HOV) lane, High Occupancy Toll (HOT) lane, Congestion Priced lane, or other feasible managed lane configurations as determined to be appropriate for a projected 2040 travel demand."

Based on the findings in the literature and my personal research work, managed lanes need to be carefully planned and designed considering common issues such as "induced demand" and "empty lane syndrome". Adding capacity to a road, when not properly managed, can induce demand which can eventually result in the same level of congestion despite the added capacity. On the other hand, a HOV/HOT lane may also suffer from underutilization or "empty lane syndrome." Also from the operational point of view, an HOV lane works better if passes through one or more recurrent bottlenecks. If an HOV lane ends prior to a bottleneck, its capability to reduce congestion by smoothing the flow of HOVs may be harmed. One example of such not properly designed HOV lanes is the HOV lane on I-5 NB in Portland, Oregon which ends about 1 mile prior to a recurrent bottleneck. In this case, the bottleneck-induced congestion backs up and blocks the outflow of the HOV lane and as a result, a queue forms in the HOV lane, just like the adjacent general purpose lanes. 

Identifying the locations of the recurrent bottlenecks on I-55 should be done prior to any initial design of the HOV/HOT lane on this corridor in order to make sure that the beginning and end points of the managed lane is properly selected.

More Processors versus Run Times


A recent blog post by Marc-André Carle suggests that "using more processors does not necessarily lead to reduced run times on CPLEX."

Running 90 models with CPLEX 12.4, he concluded (not very strongly though) that "while increasing the number of processor cores results in quicker runs on average, but the effect on individual instances is quite difficult to predict."

Complex Systems and Networks


I have recently become very interested in complex systems. My question, which is not very hard to answer, is whether transportation networks and systems are complex? I would say yes, they are.

Following is a list of some of the reasons why a system might be considered to be complex, according to a recent paper, "Challenges in Complex Systems Science", published by Dirk Helbing and his colleagues:

  • Many heterogeneous interacting parts 
  • Interactions of autonomous agents

Transportation systems are complex because they consist of many heterogeneous interacting parts and agents. For example, a public transportation system in a city consists of bus routes, rail routes, park-and-ride facilities, and so on. Just imagine a Chicagoan commuter who lives in a suburb. Every morning she drives her car, picks up a colleague on her way to a Metra station (carpooling), parks her car in a designated park-and-ride facility and both ride Metra to downtown. Then from the Metra station in downtown, they transfer to a bus to get to their office. Throughout this commute trip, different heterogeneous parts and agents are indeed interacting. As another example, bus bunching (also train bunching) is a direct result of uncoordinated interactions between different agents (buses or trains) in a public transportation system.

Other characteristics of complex systems are:
  • Path-dependent dynamics
  • Complicated transition laws
  • Self-organization or collective shifts
  • Non-equilibrium dynamics
  • Adaptivity to changing environments
  • Multilevel dynamics and so on.

Some of my recent findings on network traffic science suggest that network traffic dynamics are path-dependent. In fact, in a paper published in TRR in 2012, "Exploring Properties of Network-wide Flow-Density Relations in a Freeway Network", we suggested a path-dependent characterization of hysteresis in network traffic. Hysteretic transitions in traffic, either in macro scale on a single facility or in network scale, can be considered as complicated transitions laws. Self-organizing behavior of pedestrian crowds and the existence of the Network Fundamental Diagram (NFD) of road networks, as a collective effect of interacting vehicles in a network, are another examples.

Networks: An Introduction by Mark Newman

Networks: An Introduction
By M. E. J. Newman
Hardback, 784 pages
Oxford University Press, March 2010
ISBN13: 9780199206650
ISBN10: 0199206651


"The study of networks, including computer networks, social networks, and biological networks, has attracted an enormous amount of interest in the last few years. The rise of the Internet and the wide availability of inexpensive computers have made it possible to gather and analyze network data on an unprecedented scale, and the development of new theoretical tools has allowed us to extract knowledge from networks of many different kinds. The study of networks is broadly interdisciplinary and central developments have occurred in many fields, including mathematics, physics, computer and information sciences, biology, and the social sciences. This book brings together for the first time the most important breakthroughs in each of these fields and presents them in a coherent fashion, highlighting the strong interconnections between work in different areas. Topics covered include the measurement and structure of networks, methods for analyzing network data, including methods developed in physics, statistics, and sociology, graph theory, computer algorithms, mathematical models of networks, including random graph models and generative models, and theories of dynamical processes taking place on networks."