The Bay Bridge is San Francisco's main umbilical cord to the world, carrying 248,000 vehicles daily.
This weekend, the bridge is shut for construction. Yet, traffic is flowing decently around the bay.
Where did all the cars go? We have a clue.
Remember last summer, when the state Department of Transportation closed Interstate 5 in downtown Sacramento for weeks to do repairs?
Officials warned beforehand if people didn't change commute habits, freeways could seize with congestion, doubling commute times.
It didn't happen.
That's because many commuters made very small changes in their routes, just enough to keep life bearable for those few weeks. That's according to initial analyses by University of California, Davis, professors Pat Mokhtarian and Michael Zhang.
"The cars didn't go away," Zhang said. "Mostly, they just found other ways to go."
Nearly one-half of commuters surveyed said they left home a little bit earlier or later than usual, which took the sharp edge off the rush hour.
If their usual route was crowded or blocked, many just took the next street over.
It wasn't always pretty. Fifteenth and 16th streets had jams. Riverside and Freeport, too.
Some drivers reduced car use.
About 5 percent said they took transit more than usual. Two percent worked longer hours some days and stayed home others. (Little did they know they were practicing for furloughs!)
Two percent walked or biked more. One percent did some carpooling and vanpooling.
On the whole, it was as if commuters were guided by an instinctive choreography.
For what it's worth, Mokhtarian also found that women were more likely to change habits, trying transit or carpooling, than men.
When the closures were over, commuters went back to their old ways.
It suggests that, given appropriate advance warning, as with the Bay Bridge this weekend, drivers will adjust just enough to keep road life bearable.
How crowded are we?
The Bay Bridge, at 248,000 vehicles a day, is about the 20th busiest freeway section in the state.
The top 10 are in SoCal.
Number one? The 405 freeway in Orange County, at Highway 22, carries 374,000 vehicles daily.
Sections of I-80 in the Albany-Berkeley area rank in the 11th- to 15th-busiest range.
Sacramento? Probably not even in the top 50, Caltrans' Robert Copp reports.
Our workhorse is the W/X section of the Capital City Freeway, at 15th/16th streets – 242,000.
That's almost as much as the Bay Bridge. Caltrans' Copp seemed pretty pleased when he saw that.
"Ta-da!" he said. "Pretty good. We move an awful lot of cars in a small space."
Fine. Just don't close it down.
This story has been edited from its original version to correct the spelling of Robert Copp's name.
Call The Bee's Tony Bizjak, (916) 321-1059.
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