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TriMet halts test of audible pedestrian warning system

May 27, 2011

After nearly three months of testing an audible pedestrian warning system on 10 buses, TriMet today stopped the test because the announcement didn't activate at the appropriate time—either too soon or too late in the turn—but did activate at other times, such as when the bus was making a lane change.

The external announcement "Pedestrians, bus is turning" was in both English and Spanish and was triggered by a full rotation of the steering wheel, which caused the announcement to be too late into the turn. TriMet also tested having the announcement trigger at a half rotation of the steering wheel to test if it provided earlier warning. That activated the announcement too early, as well as during lane changes.

Review of an audible warning device was suggested as part of the comprehensive safety review initiated following last April's fatal bus crash. TriMet began the test on March 1, and after receiving feedback from operators, riders and TriMet safety and training staff, it was determined that the technology has not advanced enough to make it an effective tool to help alert pedestrians and people riding bikes that a bus is turning.

The system was not intended to change TriMet's legal and professional obligation to operate safely, be alert and scan the intersection before turning.

As the technology advances in this area, TriMet would be interested in testing an audible system in the future.