A Stunning Infographic via a Tweet - Nash, Braess, Sadik-Khan, and Me Thanks to Dewan Karim

It's always enjoyable to get a pleasant message whether through email, a phone call, in person, or even via a tweet.

I have been mourning the tragic death of John Nash while in Sweden since he influenced so much of my work and was such an extraordinary individual.

Last week, via Twitter, I received a message from Dewan Karim who tweeted the above infographic, which I thought was stunning. Obviously, it had taken him time to prepare  so I contacted him to thank him  and asked him for permission to post it in this blogpost, which he granted. Dewan tweets under Complete Mobility @DewanMKarim. He is a professional engineer and is a transportation planner in the greater Toronto area.

Not only did he include John Nash, but also Dietrich Braess, of Braess paradox fame, whom I also admire so much, and had the pleasure of hosting at the Isenberg School back in 2006.

Dewan told me that he attended the Traffic panel that I was a panelist on at the World Science Festival in NYC, which I wrote a post on.  He became very interested in the Braess paradox which I spoke on and, in particular, relative to Mayor Bloomberg shutting Broadway from 42nd to 47th Street to vehicular traffic and converting it to a pedestrian plaza.  This decision was made in conjunction with Dr. Janette Sadik-Khan.


Interestingly, I last saw Dr. Sadik-Khan, of whom I am also a big fan, when she and I were panelists together on the Transport and Traffic at The New York Times Energy for Tomorrow Conference, also in NYC, in  2013.

I like the above ninfographic so much that I will show it to my students in my Transportation and Logistics class at the Isenberg School next Fall.

In any event, it is so nice to be on the same page with researchers and a practitioner I so much admire.

Thank you, Dewan Karim!

Transportation Network Robustness in an Era of Climate Change

There has been a lot of press lately, and justifiably so, on the recent multiday closure of the San Francisco Bay Bridge and the Lake Champlain Bridge (it looks as though this one will be permanently closed). Closures of such critical transportation links have played havoc on commuting times as well as on the local economies that they connected and bridged.

There has been little attention, however, given to the impact of the deteriorating transportation infrastructure on the environment.

Our paper, Environmental Impact Assessment of Transportation Networks with Degradable Links in an Era of Climate Change, which is the lead article in a forthcoming issue of the International Journal of Sustainable Transportation, provides quantitative measures to assess the impact on the environment of transportation infrastructure deterioration. It provides environmental impact assessment indices under alternative travel behavior (either system-optimal or user-optimal) and quantifies the environmental robustness of a transportation network subject to the deterioration of the roads, including their outright removal (as in the case of bridge closures or collapses).

The paper also demonstrates that travel behavior must be included in environmental assessments of transportation network robustness and the environmental impacts. In addition, and this is quite interesting, we demonstrate that system-optimizing behavior does not necessarily lead to reduced environmental emissions! Indeed, in certain networks, letting travelers behave selfishly and letting them determine their optimal routes of travel individually with no concern for negative externalities results in lower emissions than when a central controller routes traffic so as to minimize the total travel time!

Transportation networks are simply fascinating and counterintuitive phenomena associated with them from the Braess paradox on continue to provide important subjects for research, education, and, of course, practice.