The city of Santa Rosa, California installed a bike actuated beacon to warn motorists of bicycles ahead.
Montgomery Drive in Santa Rosa is a notoriously narrow and windy road that provides the only east-west access across the city for bicyclists.
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When a cyclist bikes over a sensor embedded in the road surface near Channel Drive on Montgomery, it activates a flashing yellow light to warn following traffic of the cyclists presence.
H/T to Paul Metz.