Toward the end of the peak pm commute on Tuesday evening, the “low bridge” malfunctioned, second time in two weeks. We asked SDOT today what happened. From spokesperson Marybeth Turner:
When the bridge operator was opening the bridge to allow a vessel to pass through at 6:20 p.m., the gate on the west side that stops vehicles, bicycles and pedestrians experienced a mechanical failure. A shear pin in the internal linkage had broken.
The bridge control system is designed to always fail in a safe mode, which prevented the operator from opening the bridge. The vessels, bicycles, pedestrian and vehicles were delayed until the operator was able to make the repairs himself. The delay was approximately 67 minutes.
On June 18th we had another control system safety shut down related to the sensors that monitor the location of the bridge. This caused a 2 ½ hour delay that likely affected many of the same commuters.
We continue to look for ways to engineer more reliable systems associated with bridge openings. A delay of this length, although rare, has severe impacts on the traveling public. Detour routes for bicycles and pedestrians are not convenient.
The Spokane Street Bridge opens over 1,500 times per year with very few incidents that delay traffic due to malfunction of the bridge.