The usual permission to turn right after stopping at a red light is cancelled here. You must wait for green even if the way looks clear.
Stop and wait for the green light before turning. The sign exists because something here, a hidden approach, a busy crosswalk, makes the usual right-on-red unsafe.
This sign deletes an exception. No sign = right on red usually allowed after a full stop. Sign = wait for green.
Turning out of habit. Right-on-red is so routine that drivers stop, glance, and go without ever reading the pole beside the light.
Signs that live in the same family, or get confused with this one.
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