Owned by Caltrans and built by MCM Construction, the Yerba Buena Island (YBI) Transition Structure forms a crucial link between the world's largest Self-Anchored Suspension Span (SAS) - part of the San Francisco-Oakland Bay Bridge - and the Yerba Buena Island tunnel. The structure transitions the SAS's side-by-side road decks to the upper and lower decks of the YBI tunnel and West Span of the Bay Bridge.

Watson Bowman Acme's Wabo®MDM TransFlex expansion joint system was selected for this structure for several reasons. The system is built to withstand seismic conditions, and is capable of handling 24" of movement. The joint's design also permits access from the underside, allowing full and safe maintenance inspections and fast replacement of components if needed.

WBA's Wabo®Crete II was also added to the design to act as a sacrificial component in the event of major seismic activity, after which the Wabo®MDM TransFlex will continue to function in traffic until the header can be replaced.