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The 152/156 Improvement project reconfigured the hazardous, heavily traveled intersection of State Routes 152 and 156, dramatically enhancing safety and relieving traffic congestion. Previously, drivers on westbound 152 had to turn left across fast-moving oncoming traffic to reach westbound 156, and the accident rate at this intersection was twice the statewide average for this type of highway facility. Biggs Cardosa designed a one-lane grade-separated flyover structure that carries eastbound 152 and allows westbound 156 motorists to pass safely beneath. Biggs Cardosa’s innovative design, which included tall abutments with locked shear keys, enabled the structure to be built with a reduced bridge length, achieving considerable cost savings while still maintaining seismic safety. Another innovative solution for the project involved creating a left exit for motorists transitioning between westbound 152 and westbound 156, rather than a right exit, as is more typical on highways. This saved costs by eliminating the need for a second grade separation. Completed on budget and six weeks ahead of schedule, the flyover has greatly reduced traffic congestion and improved safety at an interchange that has long been known as one of the area’s most dangerous highway intersections. This project received the ACEC California 2009 Merit Award for Engineering Excellence, the APWA Silicon Valley Chapter 2009 Project of the Year Award and the 2010 Project of the Year in the Infrastructure category by the Northern California Chapter of the Construction Management Association of America.
