No abstract

San Francisco’s Central Freeway, which carried 93,000 commuters a day over Market Street into the Hayes Valley/Western Addition neighborhood, was shut down on August 25, 1996, so the freeway’s upper deck could be demolished as a first step in improving the seismic safety of the structure. Anticipating disastrous traffic tie-ups, local newspapers characterized the construction period in advance as “six months of traffic hell.” In an effort to mitigate the effects of the closure, the California Department of Transportation and the city of San Francisco developed a mitigation plan and implemented a wideranging public information program that included direct mailings of brochures detailing alternative travel patterns to commuters observed using the freeway. On the first day after the closure, the media braced for disaster and sent reporters to cover the expected traffic jams. When none occurred, the absence of backups became news, and politicians questioned whether the freeway was really needed. Commuters had heeded the advice of the public information campaign and spread themselves over enough routes and modes to avert large-scale delays. However, the diverted traffic brought additional congestion, delays, and potentially more accidents to the city streets in the vicinity of the freeway. The traffic patterns before and after closure are documented here, and the effectiveness of the public information program in influencing these patterns is assessed.