meaning of flashing green ball signals. Across most of Canada (Alberta, Quebec, New Brunswick, Nova Scotia, the Northwest Territories and Nunavut), flashing green means an Advanced Green. This means traffic can turn left (across oncoming traffic) without needing to yield. Ontario formerly used the Advanced Green but officially discontinued this practice on January 1, 2010. The advanced green was originally chosen to be represented by flashing green because at the time of its introduction, in Ontario, a green arrow had meant that all traffic *must turn* in the direction of the arrow, although this is no longer the case. Additionally, an advanced green could be more easily added to existing 3-lamp signals than could a green arrow, since it didn't require physically installing a fourth lamp for the arrow. an sign will often be mounted next to the signal, possibly with a corresponding (or similar) sign facing oncoming traffic. When a flashing-green phase occurs after a normal green phase, it as known as an extended green, but this sequence is much less common, as it can create a hazardous yellow trap for oncoming left turns. The US 2009 Manual on Uniform Traffic Control Devices specifically prohibits flashing any green signal indication. Protected flashing green is now used in parts of California and Ontario as part of traffic signal preemption for emergency vehicles. This does not conform to MUTCD. In Croatia and Estonia a flashing green light gives advance notice of a change to amber. Steady signals Steady green arrows Throughout most of the United States a protected turn (a turn that can be made without conflicting traffic) is indicated by a steady green arrow pointing in the direction of the turn. This indication may be displayed in a separate traffic signal head or may be in combination with other arrows or a green ball indication on the same signal such as with the Dallas Phasing configuration described below. Modern signal standards require that a yellow "clearance" interval be displayed for not less than three seconds prior to the protected turn interval ending. Throughout Canada, as in the United States, a green arrow indicates protected movement in the direction of the arrow. In British Columbia (permissive only), Alberta, Saskatchewan and Manitoba, green turn arrows may or may not flash; both cases indicate a protected turn phase, but a flashing green arrow indicates that the protected phase will be followed by a