Entropy maximization for multi-class traffic assignment published in TR-B a few days ago. Check here for an introduction  of the work and for preprint, which was posted on SSRN almost exactly a year ago.    I believe this is the first paper published by Qianni Wang as a lead author since she joined my group in 2021.  Congratulations to Qianni!

I just returned from the INFORMS Annual Conference, where I ran into several former students who are now professors across the globe—one from Europe, two from Asia, and one from the U.S.  One of them,  Yang Liu from National University of Singapore, won one of the 2023 best Transportation Science Paper Awards.  It felt surprisingly fulfilling to witness your students achieve accomplishments beyond your own.

The picture was taken with the Editor in Chief of Transportation Science, my colleague Karen Smilowitz (left), and Yang (middle)

After an extended review process that lasted nearly two years, this paper finally came out in Transportation Research Part B.  Thanks Ruijie, the first author, for his extraordinary patience and commitment to scholarship, which have become a rare commodity in today’s hyper-competitive research environment that prioritizes productivity over everything else.

A pre-print of the paper was posted in September 2022 on SSRN, under a different title and with slightly different contents.  You may check it here if you don’t have Elsevier subscription.

Aabout a week ago (on 7/19/2024), Jiayang Li defended his PhD thesis, entitled “Some New Perspectives on Games in Transportation Systems Analysis” .   His thesis has inspired a successful NSF proposal,  two publications in Transportation Science, one paper under review at Operations Research, and three conference papers in top Machine Learning conferences (ICML and NeurIPs) .

The 11th PhD student graduated from my group,  Jiayang is set to start in September as an Assistant Professor in the Department of Industrial Engineering and Manufacturing Systems at the University of Hong Kong. 

Congratulations, Dr. Li!

It so happened that four papers I co-authored came out in the past month – quite a coincidence. Here is the list.

1. A Day-to-Day Dynamical Approach to the Most Likely User Equilibrium Problem, published in Transportation Science, and to be presented in the International Symposium of Transportation and Traffic Theory next week.

2.  The sustainability appeal of urban rail transit, published in Transportation Research Part A.

3. An Autonomous Modular Public Transit service, joint work with Jane Lin and Xi Cheng at UIC, published in Transportation Research Part C, and to be presented in the International Symposium of Transportation and Traffic Theory next week.

4.Is order-2 proportionality good enough for approximating the most likely path flow in user equilibrium traffic assignment？ Joint work with Jun Xie and Liyang Feng at Southwest Jiaotong University, published in Transportation Research Part B.

Hongyu Zheng defended his Ph.D. thesis successfully today.  His thesis committee consists of Karen Smilowitz (first from the left), Jane Lin (second from left) and Hani Mahmassani (first from the right).

Hongyu is my eleventh PhD student and the tenth to complete the PhD thesis defense.  He is joining the Industrial Engineering Department at the University of Tennessee, Knoxville as a tenure-track Assistant Professor in August.

Congratulations, Hongyu!

Finally, this little C++ project that I started more than 20 years ago went open source at Github, mainly thanks to the diligence and passion of Prof. Jun Xie, a former student and now collaborator at Southwest Jiaotong University.  As of now, it contains just one traffic assignment algorithm (the greedy algorithm we developed a few years back), but the plan is to gradually release many more in the coming months.

I began to develop TNM –which stands for Toolkit for Network Modeling– in 2003.  The project is a collection of C++ code I wrote to deal with many different transportation network problems, ranging from origin-destination estimation to microscopic traffic simulation (yes, I had even written a microscopic simulator based on Cellular Automata.   It seems like an extravagant waste of time, with the benefits of hindsight).   In March 2006, when I was wrapping up my PhD research at UC Davis, I wrote a document summarizing the development up to that point, which I have since frequently quoted in my papers that use the code to produce numerical results.  You may check it here.

My development of TNM would continue well into my tenure at Northwestern.  In fact, as late as in 2015, I was still busy putting stuff into TNM.  Over the years I developed a rather flexible and universal GUI based on MFC  that has the ability to accommodate many different types of network problems — at one point I even learned to deal with GIS  functions in my GUI.  I would be lying if I tell you I did not enjoy the thrill of making a machine do what I command….  However, eventually, I realize that I must stop indulging in this hobby as it has become a black-hole swallowing an undue amount of my energy that was in short supply given my increasing seniority and the  responsibilities  that came with it  (I am sure this epiphany came to me a bit too late).

Right around the time I decided it is the time to pass the torch to the next generation, Jun showed up in my lab, first as a visiting PhD student then as a visiting postdoc.   Unlike the vast majority of my other students, he did not mind wresting with the messy C++ code I wrote in  haste.  On the contrary, he seemed to truly enjoyed it.  So, Jun gradually became involved in the development of TNM  and, after  joining Southwest Jiaotong University, has added to the development team his own graduate students.  Without Jun, the publication of TNM on github probably would never have happened.

Our paper on dockless bikesharing finally went on-line in Transportation Science.   Another uphill battle, to be sure, partly because the way we model the system was unconventional, but this time we soldiered on and prevailed in the end.  It took more than two years from the first submission to on-line publication….

If you don’t have subscription, check this post for a preprent.

The last paper I wrote with  Kenan Zhang, who graduated two years ago and is now joining EPFL as Assistant Professor, was finally published in Transportation Research Part B last week.  The paper first went on-line at SSRN in December of 2021.  So, it has been in the review process for nearly two years, during which it was reviewed by three different journals.   I am relieved the paper is finally in print; I know Kenan was exhausted by the lengthy back-and-forth with reviewers and editors.  Rewarding as the experience may be, one can only take so much for each paper without being demoralized.

The above link should work for two months.  After that, if you don’t have access to the journal, you may find a preprint here.

Our paper on ‘Accessibility-based ethics-aware transit design’ — joint work with Tianxing Dai and Jiayang Li — just appeared in Transportation Research Part B.  It took about ten months, two rounds of revisions.   Read here for more details and preprint.