The Fall and Rise of the I-35W Mississippi River Bridge – Part 1: Introduction

C: Starting Date Wednesday August 1 2007, at 6 hours, 5 minutes and 38 seconds pm

V1: Metro, fifty cars there’s report of some sort of collapse in the construction zone. North of University [Avenue]

V2: 437

V3: 551 I will be 10-8 [available for incidents] down here, she’s on her way doing triple A now

V4: 224

V5: Metro, West Metro’s going to be 10-33 [alarm sounding, emergency] at this time, all cars, fifty cars, we have a bridge collapse, the River Bridge over the Mississippi River Bridge is down

V5: 2500 do you copy?
[siren in background]

V6: 80 metro 60 cars being routed metro

V5: We will need southbound closed and northbound, both sides are down

V5: 2500 do you copy?

V7: In route 169 to 97

V8: 10-4 [ OK, I acknowledge] 1806

C: Ending Date Wednesday August at 6 hours, 6 minutes and 53 seconds pm

Note: C: is the computer time stamp, Vn: are the different voices heard on the recording. The 10 codes have been defined in [brackets]}“10-codes” are widely used by police and emergency personnel in the US to convey information, and were first published in 1940, though there is great debate as to their usefulness compared with plain speech. See Dispatch Magazine online for some discussion.

After spending 10 months on sabbatical in London studying the coevolution of transport and land use, on Tuesday July 31, 2007, my family and I returned home to Minneapolis. We had many things to do to restart a household, among them shopping. Relatives were in town for a conference, and they had rented a minivan. The next day we went to a warehouse club (Costco) to stock up on basic stores, filling the back of our vehicle with typical American middle class goods (paper towels, diapers, etc.). While we traveled to the store on what any online mapping service would suggest is the shortest path, on the return at about 3:00 pm we took West River Parkway instead of the highway to avoid traffic and have a more scenic view. That route runs along the Mississippi River, and passes immediately below the I-35W Bridge. I did not look up at the Bridge from below as we drove under it.

At 6:05 pm, CDT, August 1, 2007, the I-35W Mississippi River Bridge famously collapsed.

By 6:10 pm, I and the world knew about the collapse from watching both local news and CNN. People from around the world contacted me wishing well.

I didn’t know any of the 13 dead or 145 injured at the time, and was as surprised as anyone at the collapse, having driven under and on the Bridge many times. We discovered that it was an eight-lane truss arch bridge that had opened in 1967, and carried about 140,000 vehicles a day. Everyone in the Greater Minneapolis-St. Paul region has their own story, some heroic, most mundane. Everyone, though, remembers it.

The Regional Traffic Management Center (RTMC) in Roseville, Minnesota received news instantly, and had video cameras in the area, which they quickly pointed in the direction where once stood the Bridge. The recording of their audio inputs are transcribed in the opening quote. In the stream of random and mundane information coming into the center, communications were received about the collapse.

The next morning (August 2, 2007 – 8:24 AM) Paul Levy of the local Star Tribune newspaper reported an article with the headline (one which varied across the day and week)
4 dead, 79 injured, 20 missing after dozens of vehicles plummet into river .The article can be found online.

As with any tragedy, information as of August 2 was incomplete. People were missing, some of whom were found alive, others dead. The estimates of injured went up as better counts were made.

In the days following, I received some 17 media contacts asking about the traffic effects. My structural engineering colleagues received many, many more. As researchers, my transportation colleagues and I quickly proposed studies to examine the consequences of the collapse.

Users take infrastructure for granted. From the roots “infra” meaning below or underneath, and “structure” meaning building or assemblage, infrastructure is by its very nature not obvious, and is often hidden in plain sight. Yet its absence is noticed. Americans seldom complain about lack of on-demand electricity (blackouts), natural gas, or water, but often complain about lack of on-demand transportation capacity, which we call congestion. When construction or events close routes, so you cannot get from here to there, the complaints rise. But when infrastructure fails unexpectedly, it engenders shock rather than complaint.

Why did the Bridge collapse? And what does it say about the state of infrastructure in the United States, and for that matter, the developed world?

In a one-time event, blame is a useless exercise. My blaming you will not produce better future outcomes. But in a world with signals and repeated games, blame can lead people to behave better in the future, and the prospect of being blamed for failure may encourage behavior to avoid failure. Too much blame for failure, and insufficient reward for success, will lead to risk-averse outcomes. In some arenas, conventional finance, structural engineering, risk-aversion is probably a good idea. They provide a lattice on which the rest of society depends to accomplish their own work. The gains from innovation are likely small, the losses higher. In other areas, e.g. war, risk-aversion on the part of the weaker army may ensure defeat.

To answer the question on “Why the Bridge collapsed”, one can look to physics, and blame gravity. Blaming gravity, while technically correct in some sense, will not help us going forward.

One can look to structural engineering and blame undersized gusset plates. Or one can look to construction engineering practices and blame overloading. Or one can look to traffic engineering, and blame the need for all those people to get from A to B. Or one can look to politics, and ask why the Bridge which had (different) known problems, had not already been repaired. And so on. The layers of blame are worth exploring.

The collapse of the Bridge illustrates several different kinds of networks in action. The bridge itself was a structural network, a connection of steel and concrete elements designed (but in the end failing to) to transmit force safely from the Bridge deck to the ground. The Bridge was a link in the transportation network, an element of the limited access US Interstate Highway System enabling people to travel by car from point to point without stopping. The news of the collapse of the Bridge was transmitted over communications networks (both electronic and social), it was a quickly transmitted piece of information.


Other Parts in Series: Part 1 – IntroductionPart 2 – StructurePart 3 – CommunicationPart 4 – PoliticsPart 5 – EconomicsPart 6 – TrafficPart 7 – Replacement, Part 8 – Policy Implications