I’ve said it before and I’ll say it again: just because a turn signal is on, doesn’t mean anything. Wait and see if the turn signal indicated on the car is the movement the driver is ACTUALLY planning to make; this may involve some patience and hesitation. Assuming otherwise is such a classic way to cause a collision.
For example, when two vehicles are facing one another and both are indicating a left turn signal; are you sure the other vehicle is actually going to turn left?
Death by turn signal (part 1) – BC Driving Blog