Now when can we start tearing them down?

One phenomenon always puzzled me. Bay Bridge onramps and the streets leading up to them could be utterly gridlocked, nothing moving through several light changes, while traffic a few blocks away, though still heavy at rush hour, would flow. Traffic in the Financial District or around Union Square that was completely balled up during a Critical Mass ride would have started moving again a short time later when the Mass passed again or individual riders peeled off and doubled back.

How could this be? Shouldn’t the mighty multilane freeway have the advantage over cramped multiuse city streets?

The explanation came from an unexpected source. Ivor van Heerden is the deputy director of the Louisiana State University Hurricane Center and author of The Storm, What Went Wrong During Hurricane Katrina—The Inside Story From One Louisiana Scientist, a damning account of the levee failures in New Orleans. He happened to be giving a lecture to coincide with the book release in spring 2005 when I was volunteering in New Orleans with the Common Ground Collective, and my partner and I went.

In the middle of a blistering account of the incompetence of the Army Corps of Engineers, FEMA, the White House, and so on, van Heerden asserted that some levee failure was largely the fault of Mister Go. The New Orleanians filling the auditorium nodded knowingly, while the two dumb-ass San Franciscans stared at each other and asked, “Mister WHO?”

Mister Go is the local nickname for the Mississippi River–Gulf Outlet (MR-GO), a channel dug in 1965 to connect the Intercoastal Waterway that flows through New Orleans to the Gulf of Mexico, lopping off 40 twisty miles down the lower Mississippi. It’s known in the Crescent City as an expensive, environmentally disastrous boondoggle.

The argument van Heerden made, complete with maps and diagrams of storm surge heights and wind directions, showed how the high water driven by Katrina was concentrated at the eastern end of Mister Go and its force amplified by the narrow, deep channel that sent the water rushing west toward the city, with devastating impact on the levees. Meanwhile, miles of wetlands and barrier islands that in the past had absorbed and dispersed such storm surges had been destroyed by oil and gas exploration and development. Their beneficial effect was gone.

Suddenly, it hit me. Storm surge equals heavy traffic, Mister Go equals freeway, wetlands equals city streets. The analogy is a bit far-fetched, but it’s stood up to subsequent observation. Concentrating traffic on freeways doesn’t remove it from city streets; it just amplifies the impact in certain locations. Communities near freeway ramps know the argument that freeways help reduce traffic is garbage. Cars don’t drop onto freeways from helicopters. They clog up the ramps and spread the mess back from there.

Thanks for bringing this up, your argument is articulated perfectly.