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“it is a practice likely to cease”

By enelson
Thursday, June 15th, 2006 at 12:00 pm in Freeways, Funding, Retrofitting, Safety.

I received an interesting bit of e-mail today with the clever subject line, “Double-Decked Capriciousness?”

Reader John G. took issue with my story about the 50th anniversary of Dwight D. Eisenhower’s Interstate Highway System, in which I attempted to put the freeway system into perspective with the help of Rod Diridon, executive director of the Mineta Transportation Institute:

“The real crisis we’re facing is that coming in and out of our metropolitan areas,” he said. Interstates are “all built out to the sound walls,” and solutions like double decking aren’t viable after the deadly collapse of Interstate 880 in he 1989 Loma Prieta Earthquake.

I-880 collapse.jpg

“We will need every bit of highway capacity that we can get our hands on … but at the same time, the population is going to double by 2040 and we’re never going to be able to sustain the trip requirements on available highways.”

John defended the double-deckers thusly:

The 280 extension immediately north of US 101 in San
Francisco is a seismically-sound double-decked freeway
with modern box girders, etc. Even the much less sound double-decked Central Freeway didn’t collapse in the Loma Prieta Earthquake.

Please save caprice for your column.

I like the sound of that. “Column.” Maybe they should pay me more for blogging.

But John raises a good point. If we can retrofit and rebuild the Bay Bridge and such things as towering viaducts to be seismically sound, why can’t we build double-deck freeways that are safe enough to withstand an 8.0 magnitude quake?

My first thought was that, because of the memory of the Cypress freeway structure crushing all those people, we don’t want to go there again. In rebuilding the Bay Bridge West Approach, Caltrans is removing as much double-decking as it can, and the Central has been similarly reconfigured.

I Googled a BBC Website that had a video of its newscast from the time, in which reporter Martin Bell said that people had questions “about why, in this most earthquake-conscious part of the country, they build one freeway on top of another. it is a practice likely to cease.”

Metropolitan Transportation Commission spokesman Randy Rentschler only partly confirmed my assumption, however.

“It’s true that the 280 is a much safer roadway, but people forget that it was an incredibly expensive freeway,” costing around a quarter-billion dollars.

The other point is that Loma Prieta was not “The Big One,” was far away and still managed to make freeway collapse.

For enough money, you can make it safer. But will that be safe enough to keep motorists from nervously looking up now and then?

The reason freeways were double-decked in the first place was to save money on land, according to Randy. When you add up the cost of seismic safety, those savings disappear.

Add to that the reason that people in the San Fernando Valley don’t want their Ventura Freeway double-decked, despite its world-class traffic jams.

As Randy puts it, “you have to look at the darn thing.”

But I’d love to know what everyone else thinks about this. Do Caltrans engineers dream of a new generation of double-deckers in the Bay Area? Would most commuters set aside their fear for a smooth ride on the I-880?

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