On october 17, 1989, the upper deck of the i-880 elevated freeway structure between 18th and 34th streets in oakland, california, collapsed because of the loma prieta earthquake. The collapse of this cypress viaduct severed the major artery, disrupting local and regional transportation. An interim replacement for the cypress viaduct could not be put in place because of community opposition, so the california department of transportation (caltrans) had to develop interim traffic system management (tsm) measures to relieve severely congested freeways. The innovative network-based methodology used to analyze the interim tsm alternatives proposed by caltrans is described, and the alternatives' projected effectiveness in relieving congestion on freeways and arterials in oakland is examined. The analysis used performance-based ranking to select the alternatives that would qualify for fhwa emergency relief funding. The examination of resultsfrom various combinations of alternatives is included, and the phenomenon called synergistic effect is introduced as a measure of effectiveness to rank the combinations. The need for simultaneous improvement of arterials, ramp metering, and freeways to achieve optimum delay reduction and freeway congestion relief is also discussed. The synergistic effects of the combined alternatives are compared, and the projects approved by fhwa are listed. This paper appears in transportation research record no. 1327, Visibility, rail-highway grade crossings, and highway improvement evaluation 1991
Abstract