Network Vulnerability in Large-Scale Transportation Networks

Transportation networks are the lifelines in times of peace and prosperity as well as during and post disasters.

From roads to bridges, and whether by land, air, or sea, and via different modes of transportation, such networks provide the connectivity for the movement of people, goods, and services.

When Professor Michael Taylor of the University of South Australia in Adelaide issued a call for papers for a special issue of the journal Transportation Research A on Network Vulnerability in Large-Scale Transport Networks, my co-author of the Fragile Networks book, Dr. Patrick Qiang, and I knew that, given the timeliness of this special issue, we hoped to make a contribution.

We are delighted that we have heard from Professor Taylor who has let us know that the special issue is now in production with the publisher of the journal, Elsevier.

The papers in the special issue are:

Jenelius, E and Matsson, L-G, Road network vulnerability analysis of area-covering disruptions: a grid-based approach with case study

Taylor, M A P and Susilawati, S, Remoteness and accessibility in the vulnerability analysis of regional road networks

Watling, D and Balijepalli, N, A method to assess demand growth vulnerability of travel times on road network links

Bell, M G H, Trozzi, V, Hosseinloo, S-H, Gentile, G and Fonzone, A, Time-dependent Hyperstar algorithm for robust vehicle navigation in time-dependent stochastic road networks

Qiang, Q and Nagurney, A, A bi-criteria indicator to assess supply chain network performance for critical needs under capacity and demand disruptions

Nagae, T, Fujihara, T and Asakura, Y, Anti-seismic reinforcement strategy for urban road networks

Snelder, M, Van Zuylen, H and Immers, B, A framework for robustness analysis of road networks for short term variations in supply

Knoop, V, Snelder, M, Van Zuylen, H J, and Hoogendoorn, S P, Link-level vulnerability indicators for real-world networks

According to Professor Taylor: These are all excellent papers and define the global interest in vulnerability analysis. The special issue should be of wide interest.

Our paper in this special issue focuses on critical needs product supply chains. Critical needs products are those products and supplies that are essential to human health and life. Examples include food, water, medicines, and vaccines. The demand for critical needs is always present and, hence, the disruption to the production, storage, transportation/distribution, and ultimate delivery of such products can result not only in discomfort and human suff ering but also in loss of life.

Critical needs supply chains also play a pivotal role during and post disasters during which severe disruptions can be expected to have occurred. Indeed, the past few decades have visibly demonstrated that disasters, whether natural or man-made, may severely damage infrastructure networks, such as transportation and logistical networks, may cause great loss to human life, and also may result in tremendous damage to a nation's economy.

In our paper, we develop a supply chain/logistics network model for critical needs in the case of disruptions. The objective is to minimize the total network costs, which are generalized costs that may include the monetary, risk, time, and social costs. The model assumes that disruptions may have an impact on both the network link capacities as well as on the product demands. Two diff erent cases of disruption scenarios are considered. In the first case, we assume that the impacts of the disruptions are mild and that the demands can
be met. In the second case, the demands cannot all be satis fied. For these two cases, we propose two individual performance indicators. We then construct a bi-criteria indicator to assess the supply chain network performance for critical needs. An algorithm is described which is applied to solve a spectrum of numerical examples in order to illustrate the new concepts.

Supply Chain Disruptions, Congestion, Risk, and Foreign Affairs

Kyle Johnson, who was a Jack Welch Scholar at UMass Amherst, and graduated from the Isenberg School with a degree in Operations Management, and now works in high tech recycling, sent me an email message this past week that he thought of me when he was reading an article in Foreign Affairs and provided me with the link to it.

The article, "Japan's Disaster and the Manufacturing Meltdown -- What the Earthquake and Tsunami Revealed About Globalization," by Marc Levinson, highlights the dangers of single sourcing that the Japan triple disaster has painfully shown, which has impacted the automotive and high tech industries severely. Levinson also noted his 2008 article in Foreign Affairs, in which he presciently wrote:

“Congested shipping lanes and highways make transit times uncertain,” “and this uncertainty hurts profits.” Moreover, the push for ever-greater port security will further slow transit; physical inspection of shipping containers could delay delivery by two to three days or more. “Even if the proportion of containers pulled out of the flow of traffic is small, importers will be forced to reckon with the possibility that their goods might be delayed in transit. In some instances, importers will adjust by keeping more stocks in their U.S. warehouses at any one time.”

Just think of all the time that is now being spent to check for radiation of goods being imported from Japan!

In 2009, Drs. Qiang, Dong, and I wrote the article, Modeling of Supply Chain Risk Under Disruptions with Performance Measurement and Robustness Analysis, which appeared in the book, Managing Supply Chain Risk and Vulnerability: Tools and Methods for Supply Chain Decision Makers, T. Wu and J. Blackhurst, Editors, Springer, Berlin, Germany, pp 91-111. Our study extended previous supply chain research by capturing supply-side disruption risks, transportation and other cost risks, and demand-side uncertainty within an integrated modeling and robustness analysis framework. Moreover, we included congestion in the model and proposed a weighted performance measure to evaluate different supply chain disruptions.

Highlights of other research on supply chain risk I wrote about in an earlier blogpost, which was motivated by, in part, the frustration at the developing events in Japan and the suffering of the people there.

In our Fragile Network Economy, the identification of the performance of supply chain networks prior to disruptions and the determination of which nodes and links really matter needs to be done before disasters strike!

Lean manufacturing may be more than short-sided, it may be, frankly, foolish.

Supply Chain Disruptions and New Book

In the post below, I noted that I have organized an invited session, which will take place this Monday, at the Math Programming Symposium in Chicago. In the session, we have a presentation on supply chain risk management and vulnerability analysis, joint with Professor Patrick Qiang of Penn State University in Malvern, and Professor June Dong of SUNY Oswego. The paper that we are presenting on this topic will appear in a new book, out shortly, entitled Managing Supply Chain Risk and Vulnerability, which is edited by Professors Teresa Wu and Jennifer Blackhurst. If you click here, you will also find the table of contents, which includes our chapter, and the chapter by another Virtual Center for Supernetworks Associate, Professor Jose M. Cruz of UCONN at Storrs, who contributed a chapter on network relationships. We congratulate Professors Wu and Blackhurst on the completion of this volume!

Here is the preprint of our supply chain risk paper, which captures uncertainty associated with production costs, as well as distribution and transportation costs in multitiered supply chain networks, in which the individual behavior of the decision-makers is modeled, along with the prices that the consumers are willing to pay for the product in the case of random demands. In addition, we define robustness in this setting and provide a supply chain network performance measure.

An expansion of this chapter, with additional motivation and case examples, appears in our book, Fragile Networks: Identifying Vulnerabilities and Synergies in an Uncertain World, where we also model network systems and their vulnerability from transportation networks to the Internet, electric power supply chains, and even financial networks! In addition, we demonstrate, how through network integration, one may identify a priori, any possible synergies, which can greatly assist in the evaluation of potential mergers and/or acquisitions.