Wednesday, May 8, 2013

The Milk Run Load Paradox -- Beware of Bad Environmental Policies

Who is not fascinated by paradoxes!

As a researcher and educator in networks, I have done a lot of work on the Braess paradox, and even had the honor of translating, along with him and Tina Wakolbinger, the classic 1968 article by Braess (from German to English). Tina, at that time was my doctoral student  (and is now a Full Professor). Below is a photo of the three of us taken in my Supernetworks Lab in 2006 at the Isenberg School at UMass Amherst, after our translation was published in 2005 in Transportation Science. Professor Braess traveled from Germany to visit us. That year I was on sabbatical as a Science Fellow at the Radcliffe Institute for Advanced Studies at Harvard.

This intriguing paradox, which shows that how humans interact with infrastructure (transportation in the original version), matters in that the addition of a new road/route may make travelers all worse off in terms of an increase in travel time (under user-optimizing behavior).

I have spoken on this paradox and examples in the real world at the World Science Festival in NYC (great fun), and was interviewed on the topic for the PBS America Revealed video on gridlock by the winner of Survivor (2006), Yul Kwon (tons of fun). I have also written invited OpEds on the topic, including one for Resources for the Future.

Recently, I had the honor of being a panelist on Traffic and Transport at The New York Times Energy for Tomorrow conference with the theme of Building Sustainable Cities (a true intellectual feast with great panelists and discussions that continue to this day in blogs and through emails and phone conversations). Some quotes were captured in this nice post from the IEEE Spectrum EnergyWise blog (thanks)!

Joe Nocera of The New York Times, who needs no introduction, was our panel moderator and I noted transport policies, dating to ancient Roman times, the Braess paradox, and also highlighted the importance of freight to cities' sustainability. I mentioned my experiences of living in Gothenburg, Sweden, as a Visiting Professor, and the discovery there by a doctoral student, Niklas Arvidsson, of the milk run load paradox.

Today, I heard from Niklas, who shared with me that his paper was published in Transportation Research A and he provided me with a reprint. The paper, "The milk run revisited: A load factor paradox with economic and environmental implications for urban freight transport," shows that how you route a truck on a milk run (think of sequential deliveries as a milk truck would do in a bygone era) matters environmentally. Certain governmental policies internationally have focused on increasing throughput of freight but actually having a higher load over a longer distance may add to the environmental emissions so, contrary to certain policies,  it may be better to take the route where you can offload your cargo (milk) as soon as possible.

Today I also received a copy of Niklas Arvidsson's dissertation from the School of Business, Economics and Law at the University of Gothenburg. His supervisor is Professor Johan Woxenius and I am the co-supervisor. It is such an honor to be visiting this great group of researchers in transport and logistics who also have terrific practical insights.

Research discoveries illuminate and intrigue and make you stop and think -- Wow! congrats to Mr. Arvidsson on such an important and exciting result and on the publication of his paper in Transportation Research A!

I'll be back in Sweden soon for the defense and to celebrate.

And, coincidentally, paradoxes must be "in the air," since my fellow INFORMS member and WORMS President, Professor Laura McLay, just today posted on the Braess paradox -- thanks for the acknowledgment.