Seattle Flashing Yellow BallThe City of Seattle uses the flashing yellow ball to indicate the permissive left-turn interval at approximately 20 installations, four of which have been added in the past year. Seattle is now using a four-section vertical head that has a red ball, a yellow ball, a flashing yellow ball, and a variable indication yellow arrow/green arrow section. Typically these locations are operated in a protected/permissive mode. The flashing circular yellow indication has been in use since about 1966. None of these displays are used with lead/lag left-turn phasing.
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