UC Berkeley Press Release

New report finds "traffic nightmare" if BART service knocked out

By Sarah Yang, Media Relations | 13 October 2004

BERKELEY – A halting of BART service would trigger a complete traffic gridlock on Bay Area corridors, according to a new, sobering analysis by transportation researchers at the University of California, Berkeley.

The study, to be released tomorrow (Thursday, Oct. 14), looks at the impact on rush hour traffic if BART service, particularly the stretch through the 3.6-mile, steel and concrete tube under the San Francisco Bay, were no longer available.

"If the Transbay Tube were out of commission and people were forced to hit the road, there would be a traffic nightmare on major Bay Area corridors and nearby city streets," said Jorge Laval, lead author of the report and a recent Ph.D. graduate from UC Berkeley. "The mess on the freeways would spill over to city streets, and that makes things even worse. In many cases, drivers would likely spend one to two hours on city streets just to get to the freeway, crawling at speeds as low as two miles per hour."

Hard-hit commutes would include the span from Pittsburg to I-80 via Highway 4, which would take 165 minutes instead of the usual 30 minutes. Travel times from I-680 to Highway 13, via Highway 24 through the Caldecott Tunnel, would go from 24 minutes to 195 minutes, eight times longer than normal.

While it is no surprise that crippling the Bay Area's primary public transit system would have detrimental ripple effects on roadways, this report is the first to systematically quantify the traffic delays.

BART supports an estimated 320,000 riders every day. Nearly half of those riders, 150,000 people, travel through the Transbay Tube, which opened to the public 30 years ago.

BART commissioned the study in response to numerous media and public requests over the years asking to quantify the impact of an extended BART service interruption on Bay Area commutes.

The study comes days before the 15th anniversary of the Loma Prieta earthquake. The magnitude 6.9 earthquake hit the Bay Area on Oct. 17, 1989, killing at least 63 people and injuring more than 3,750 others, destroying the Cypress freeway in Oakland and causing an estimated $5.9 billion in property damage.

"We found that the peak morning rush hour will go from two hours starting at 7 a.m. to a staggering seven hours, so half the workday would be gone by the time drivers step out of their cars," said Michael Cassidy, UC Berkeley professor of civil engineering and co-author of the report. "We didn't analyze the impacts on labor, but it's hard to imagine how such a serious traffic mess would not put a dent into worker productivity."

Other results from the study indicate that without BART transbay service, congestion from the Bay Bridge westbound in the morning would create backups stretching 26 miles with vehicles traveling as slowly as 9 miles per hour. In the afternoon, heading east, the Bay Bridge backup would stretch 31 miles with an average travel speed of 11 miles per hour.

"Our findings underscore how dependent the Bay Area is on a properly functioning transit system," said Laval.

The authors used BART ridership data, including the origin and destination of trips, from the 2003 calendar year. They also used data from a sampling of weekdays from 2003 through September 2004 from the California Freeway Performance Measurement System, or PeMS.

The PeMS project, which uses sensors embedded in the freeway to provide historic and real-time data on traffic volume and bottleneck capacities, is run by the UC Berkeley Department of Electrical Engineering and Computer Sciences in cooperation with the California Department of Transportation.

In addition, the authors used data from 511.org, a source for San Francisco Bay Area traffic information, including current traffic speeds and delays.

Juan-Carlos Herrera, a UC Berkeley graduate student in civil engineering, also co-authored this report.