People talk about double-decking freeways (such as the I-405 or US 101) as if it is the solution to all widening problems. Similarly, people talk about tunnels as a solution. Both have a serious risk you never hear mentioned, and I’m not talking about earthquakes.
I’m talking accidents and fire. This was just demonstrated graphically yesterday (see the pictures), after a tractor trailer hauling 8,600 gallons of gasoline crashed into a pylon on an interchange connecting westbound lanes of I-80, which includes the Bay Bridge, to southbound I-880 in Oakland. It ignited and the fire led to the collapse of a second interchange from eastbound I-80 to eastbound I-580 located above the first interchange. Specifically, a section of the roadway taking traffic from the Bay Bridge onto eastbound I-580 fell onto the connector that brings East Bay traffic from I-80 to I-880 and I-580. Lanes of I-580 near the East Bay Municpal Utility District sewage treatment plant at the maze are draped like a blanket over the northeast edge of the freeway below with the corner tip touching the ground below that.
[SF Chronicle report, LA Daily News report, Closures and Alternate Routes]
As for the truck? It seems to have disappeared. One Caltrans worker at the scene held up his thumb and forefinger an inch apart to describe how big the tanker is now. The driver, who suffered 2nd degree burns, got out of the truck on his own after it overturned, hailed a taxi to a nearby hospital, where he is in critical but stable condition.
This is why I believe that automated fire suppression systems are so important for any overpass, double-decked section, or tunnel. Even my idea for widening US-101 with minimal property loss* has automated sprinkler systems. Caltrans tends not to build these, which is one reason I don’t like double-decking or long tunnels, such as are proposed for I-710 or the Route 74 tunnel.
* So what’s my idea. Create an elevated roadbed, ideally from the start of US 101 downtown and continuing to Route 27. This roadbed would be for long distance traffic only. There would be interchanges only near other freeways, or perhaps half-way between freeways. Entrance and exit to this upper roadbed would be from the current #1 lane (ramps up and down), and the laning would be reversed on the upper roadbed (i.e., the outer lanes would be the fast lanes). The upper roadbed would be reserved for HOV and long-distance traffic only. Further, there would be a fire-suppression system built into the roadbed such that a detected fire in the lower roadbed would (a) signal the fire department, and (b) dump appropriate suppression chemicals and foam, if the fire was burning long enough.