Oakland Wye

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The Oakland Wye is an underground flying junction in downtown Oakland that lets BART trains switch between lines. It sits mainly under Broadway and 9th Streets and is the center of the BART system, since almost every regular train passes through it.

From the wye, trains can go to three directions: northbound to the Richmond or Antioch lines, westbound to San Francisco, and southbound to Berryessa or Dublin/Pleasanton. The first stations nearby are 12th Street Oakland City Center (underground) for northbound trains, West Oakland (elevated) for westbound trains, and Lake Merritt (underground) for southbound trains.

The wye has three tracks with a central MX/CX track that adds capacity between West Oakland and 12th Street. This MX/CX track is usually used by Antioch-bound trains. There are emergency access points at 7th & Broadway and a sidewalk hatch at 9th & Harrison for the A and M or A and C lines.

Speed through the Wye was meant to be 27 mph, but design problems forced a lower limit of 18 mph on most tracks. The CX track between West Oakland and 12th Street can run faster, up to 36 mph. The original plan placed the wye under Broadway and 8th Street, but it was changed to Broadway and 9th Street, which required tighter turns and contributed to the lower speeds.

A third MX/CX track was completed in 1986, linking West Oakland, 12th Street, 19th Street, and MacArthur. It was initially used for peak-hour service, but since 1992 it has mostly carried eastbound Yellow Line trains to enable cross-platform transfers with the Orange Line.

There have been notable problems at the wye: in 1992, a southbound train temporarily on a northbound track due to maintenance caused injuries; in 2000, automatic train controls failed and trains had to operate manually and slowly; and in 2009 two northbound trains collided and derailed while merging near the wye.

People have proposed bypasses to connect MacArthur and Oakland Coliseum directly with the Transbay Tube to provide express service and reduce the wye’s system-wide impact. The idea of additional infill stations or more frequent service in the urban core could also come from turnback operations within the Oakland Wye.